perl/Porting/Glossary

!!!!!!!   DO NOT EDIT THIS FILE   !!!!!!!
This file is built by metaconfig.

This file contains a description of all the shell variables whose value is
determined by the Configure script.  Variables intended for use in C
programs (e.g. I_UNISTD) are already described in config_h.SH.  [`configpm'
generates pod documentation for Config.pm from this file--please try to keep
the formatting regular.]

_a (Unix.U):
	This variable defines the extension used for ordinary library files.
	For unix, it is '.a'.  The '.' is included.  Other possible
	values include '.lib'.

_exe (Unix.U):
	This variable defines the extension used for executable files.
	DJGPP, Cygwin and OS/2 use '.exe'.  Stratus VOS uses '.pm'.
	On operating systems which do not require a specific extension
	for executable files, this variable is empty.

_o (Unix.U):
	This variable defines the extension used for object files.
	For unix, it is '.o'.  The '.' is included.  Other possible
	values include '.obj'.

afs (afs.U):
	This variable is set to 'true' if AFS (Andrew File System) is used
	on the system, 'false' otherwise.  It is possible to override this
	with a hint value or command line option, but you'd better know
	what you are doing.

afsroot (afs.U):
	This variable is by default set to '/afs'. In the unlikely case
	this is not the correct root, it is possible to override this with
	a hint value or command line option.  This will be used in subsequent
	tests for AFSness in the configure and test process.

alignbytes (alignbytes.U):
	This variable holds the number of bytes required to align a
	double-- or a long double when applicable. Usual values are
	2, 4 and 8.  The default is eight, for safety.

aphostname (d_gethname.U):
	This variable contains the command which can be used to compute the
	host name. The command is fully qualified by its absolute path, to make
	it safe when used by a process with super-user privileges.

api_revision (patchlevel.U):
	The three variables, api_revision, api_version, and
	api_subversion, specify the version of the oldest perl binary
	compatible with the present perl.  In a full version string
	such as '5.6.1', api_revision is the '5'.
	Prior to 5.5.640, the format was a floating point number,
	like 5.00563.

	perl.c:incpush() and lib/lib.pm will automatically search in
	$sitelib/.. for older directories back to the limit specified
	by these api_ variables.  This is only useful if you have a
	perl library directory tree structured like the default one.
	See INSTALL for how this works.  The versioned site_perl
	directory was introduced in 5.005, so that is the lowest
	possible value.  The version list appropriate for the current
	system is determined in inc_version_list.U.

	XXX To do:  Since compatibility can depend on compile time
	options (such as bincompat, longlong, etc.) it should
	(perhaps) be set by Configure, but currently it isn't.
	Currently, we read a hard-wired value from patchlevel.h.
	Perhaps what we ought to do is take the hard-wired value from
	patchlevel.h but then modify it if the current Configure
	options warrant.  patchlevel.h then would use an #ifdef guard.

api_subversion (patchlevel.U):
	The three variables, api_revision, api_version, and
	api_subversion, specify the version of the oldest perl binary
	compatible with the present perl.  In a full version string
	such as '5.6.1', api_subversion is the '1'.  See api_revision for
	full details.

api_version (patchlevel.U):
	The three variables, api_revision, api_version, and
	api_subversion, specify the version of the oldest perl binary
	compatible with the present perl.  In a full version string
	such as '5.6.1', api_version is the '6'.  See api_revision for
	full details.  As a special case, 5.5.0 is rendered in the
	old-style as 5.005.  (In the 5.005_0x maintenance series,
	this was the only versioned directory in $sitelib.)

api_versionstring (patchlevel.U):
	This variable combines api_revision, api_version, and
	api_subversion in a format such as 5.6.1 (or 5_6_1) suitable
	for use as a directory name.  This is filesystem dependent.

ar (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the ar program.  After Configure runs,
	the value is reset to a plain "ar" and is not useful.

archlib (archlib.U):
	This variable holds the name of the directory in which the user wants
	to put architecture-dependent public library files for $package.
	It is most often a local directory such as /usr/local/lib.
	Programs using this variable must be prepared to deal
	with filename expansion.

archlibexp (archlib.U):
	This variable is the same as the archlib variable, but is
	filename expanded at configuration time, for convenient use.

archname (archname.U):
	This variable is a short name to characterize the current
	architecture.  It is used mainly to construct the default archlib.

archname64 (use64bits.U):
	This variable is used for the 64-bitness part of $archname.

archobjs (Unix.U):
	This variable defines any additional objects that must be linked
	in with the program on this architecture.  On unix, it is usually
	empty.  It is typically used to include emulations of unix calls
	or other facilities.  For perl on OS/2, for example, this would
	include os2/os2.obj.

asctime_r_proto (d_asctime_r.U):
	This variable encodes the prototype of asctime_r.
	It is zero if d_asctime_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_asctime_r
	is defined.

awk (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the awk program.  After Configure runs,
	the value is reset to a plain "awk" and is not useful.

baserev (baserev.U):
	The base revision level of this package, from the .package file.

bash (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

bin (bin.U):
	This variable holds the name of the directory in which the user wants
	to put publicly executable images for the package in question.  It
	is most often a local directory such as /usr/local/bin. Programs using
	this variable must be prepared to deal with ~name substitution.

bin_ELF (dlsrc.U):
	This variable saves the result from configure if generated binaries
	are in ELF format. Only set to defined when the test has actually
	been performed, and the result was positive.

binexp (bin.U):
	This is the same as the bin variable, but is filename expanded at
	configuration time, for use in your makefiles.

bison (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the bison program.  After Configure runs,
	the value is reset to a plain "bison" and is not useful.

byacc (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the byacc program.  After Configure runs,
	the value is reset to a plain "byacc" and is not useful.

byteorder (byteorder.U):
	This variable holds the byte order in a UV. In the following,
	larger digits indicate more significance.  The variable byteorder
	is either 4321 on a big-endian machine, or 1234 on a little-endian,
	or 87654321 on a Cray ... or 3412 with weird order !

c (n.U):
	This variable contains the \c string if that is what causes the echo
	command to suppress newline.  Otherwise it is null.  Correct usage is
	$echo $n "prompt for a question: $c".

castflags (d_castneg.U):
	This variable contains a flag that precise difficulties the
	compiler has casting odd floating values to unsigned long:
	0 = ok
	1 = couldn't cast < 0
	2 = couldn't cast >= 0x80000000
	4 = couldn't cast in argument expression list

cat (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the cat program.  After Configure runs,
	the value is reset to a plain "cat" and is not useful.

cc (cc.U):
	This variable holds the name of a command to execute a C compiler which
	can resolve multiple global references that happen to have the same
	name.  Usual values are 'cc' and 'gcc'.
	Fervent ANSI compilers may be called 'c89'.  AIX has xlc.

cccdlflags (dlsrc.U):
	This variable contains any special flags that might need to be
	passed with 'cc -c' to compile modules to be used to create a shared
	library that will be used for dynamic loading.  For hpux, this
	should be +z.  It is up to the makefile to use it.

ccdlflags (dlsrc.U):
	This variable contains any special flags that might need to be
	passed to cc to link with a shared library for dynamic loading.
	It is up to the makefile to use it.  For sunos 4.1, it should
	be empty.

ccflags (ccflags.U):
	This variable contains any additional C compiler flags desired by
	the user.  It is up to the Makefile to use this.

ccflags_uselargefiles (uselfs.U):
	This variable contains the compiler flags needed by large file builds
	and added to ccflags by hints files.

ccname (Checkcc.U):
	This can set either by hints files or by Configure.  If using
	gcc, this is gcc, and if not, usually equal to cc, unimpressive, no?
	Some platforms, however, make good use of this by storing the
	flavor of the C compiler being used here.  For example if using
	the Sun WorkShop suite, ccname will be 'workshop'.

ccsymbols (Cppsym.U):
	The variable contains the symbols defined by the C compiler alone.
	The symbols defined by cpp or by cc when it calls cpp are not in
	this list, see cppsymbols and cppccsymbols.
	The list is a space-separated list of symbol=value tokens.

ccversion (Checkcc.U):
	This can set either by hints files or by Configure.  If using
	a (non-gcc) vendor cc, this variable may contain a version for
	the compiler.

cf_by (cf_who.U):
	Login name of the person who ran the Configure script and answered the
	questions. This is used to tag both config.sh and config_h.SH.

cf_email (cf_email.U):
	Electronic mail address of the person who ran Configure. This can be
	used by units that require the user's e-mail, like MailList.U.

cf_time (cf_who.U):
	Holds the output of the "date" command when the configuration file was
	produced. This is used to tag both config.sh and config_h.SH.

charbits (charsize.U):
	This variable contains the value of the CHARBITS symbol, which
	indicates to the C program how many bits there are in a character.

charsize (charsize.U):
	This variable contains the value of the CHARSIZE symbol, which
	indicates to the C program how many bytes there are in a character.

chgrp (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

chmod (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the chmod program.  After Configure runs,
	the value is reset to a plain "chmod" and is not useful.

chown (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

clocktype (d_times.U):
	This variable holds the type returned by times(). It can be long,
	or clock_t on BSD sites (in which case <sys/types.h> should be
	included).

comm (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the comm program.  After Configure runs,
	the value is reset to a plain "comm" and is not useful.

compiler_warning (compiler_warning.U):
	This variable holds the command to check if the file specified as a
	parameter contains a compiler warning

compress (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

config_arg0 (Options.U):
	This variable contains the string used to invoke the Configure
	command, as reported by the shell in the $0 variable.

config_argc (Options.U):
	This variable contains the number of command-line arguments
	passed to Configure, as reported by the shell in the $# variable.
	The individual arguments are stored as variables config_arg1,
	config_arg2, etc.

config_args (Options.U):
	This variable contains a single string giving the command-line
	arguments passed to Configure.	Spaces within arguments,
	quotes, and escaped characters are not correctly preserved.
	To reconstruct the command line, you must assemble the individual
	command line pieces, given in config_arg[0-9]*.

contains (contains.U):
	This variable holds the command to do a grep with a proper return
	status.  On most sane systems it is simply "grep".  On insane systems
	it is a grep followed by a cat followed by a test.  This variable
	is primarily for the use of other Configure units.

cp (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the cp program.  After Configure runs,
	the value is reset to a plain "cp" and is not useful.

cpio (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

cpp (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the cpp program.  After Configure runs,
	the value is reset to a plain "cpp" and is not useful.

cpp_stuff (cpp_stuff.U):
	This variable contains an identification of the concatenation mechanism
	used by the C preprocessor.

cppccsymbols (Cppsym.U):
	The variable contains the symbols defined by the C compiler
	when it calls cpp.  The symbols defined by the cc alone or cpp
	alone are not in this list, see ccsymbols and cppsymbols.
	The list is a space-separated list of symbol=value tokens.

cppflags (ccflags.U):
	This variable holds the flags that will be passed to the C pre-
	processor. It is up to the Makefile to use it.

cpplast (cppstdin.U):
	This variable has the same functionality as cppminus, only it applies
	to cpprun and not cppstdin.

cppminus (cppstdin.U):
	This variable contains the second part of the string which will invoke
	the C preprocessor on the standard input and produce to standard
	output.  This variable will have the value "-" if cppstdin needs
	a minus to specify standard input, otherwise the value is "".

cpprun (cppstdin.U):
	This variable contains the command which will invoke a C preprocessor
	on standard input and put the output to stdout. It is guaranteed not
	to be a wrapper and may be a null string if no preprocessor can be
	made directly available. This preprocessor might be different from the
	one used by the C compiler. Don't forget to append cpplast after the
	preprocessor options.

cppstdin (cppstdin.U):
	This variable contains the command which will invoke the C
	preprocessor on standard input and put the output to stdout.
	It is primarily used by other Configure units that ask about
	preprocessor symbols.

cppsymbols (Cppsym.U):
	The variable contains the symbols defined by the C preprocessor
	alone.  The symbols defined by cc or by cc when it calls cpp are
	not in this list, see ccsymbols and cppccsymbols.
	The list is a space-separated list of symbol=value tokens.

crypt_r_proto (d_crypt_r.U):
	This variable encodes the prototype of crypt_r.
	It is zero if d_crypt_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_crypt_r
	is defined.

cryptlib (d_crypt.U):
	This variable holds -lcrypt or the path to a libcrypt.a archive if
	the crypt() function is not defined in the standard C library. It is
	up to the Makefile to use this.

csh (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the csh program.  After Configure runs,
	the value is reset to a plain "csh" and is not useful.

ctermid_r_proto (d_ctermid_r.U):
	This variable encodes the prototype of ctermid_r.
	It is zero if d_ctermid_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_ctermid_r
	is defined.

ctime_r_proto (d_ctime_r.U):
	This variable encodes the prototype of ctime_r.
	It is zero if d_ctime_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_ctime_r
	is defined.

d__fwalk (d__fwalk.U):
	This variable conditionally defines HAS__FWALK if _fwalk() is
	available to apply a function to all the file handles.

d_accept4 (d_accept4.U):
	This variable conditionally defines HAS_ACCEPT4 if accept4() is
	available to accept socket connections.

d_access (d_access.U):
	This variable conditionally defines HAS_ACCESS if the access() system
	call is available to check for access permissions using real IDs.

d_accessx (d_accessx.U):
	This variable conditionally defines the HAS_ACCESSX symbol, which
	indicates to the C program that the accessx() routine is available.

d_acosh (d_acosh.U):
	This variable conditionally defines the HAS_ACOSH symbol, which
	indicates to the C program that the acosh() routine is available.

d_aintl (d_aintl.U):
	This variable conditionally defines the HAS_AINTL symbol, which
	indicates to the C program that the aintl() routine is available.
	If copysignl is also present we can emulate modfl.

d_alarm (d_alarm.U):
	This variable conditionally defines the HAS_ALARM symbol, which
	indicates to the C program that the alarm() routine is available.

d_archlib (archlib.U):
	This variable conditionally defines ARCHLIB to hold the pathname
	of architecture-dependent library files for $package.  If
	$archlib is the same as $privlib, then this is set to undef.

d_asctime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_ASCTIME64 symbol, which
	indicates to the C program that the asctime64 () routine is available.

d_asctime_r (d_asctime_r.U):
	This variable conditionally defines the HAS_ASCTIME_R symbol,
	which indicates to the C program that the asctime_r()
	routine is available.

d_asinh (d_asinh.U):
	This variable conditionally defines the HAS_ASINH symbol, which
	indicates to the C program that the asinh() routine is available.

d_atanh (d_atanh.U):
	This variable conditionally defines the HAS_ATANH symbol, which
	indicates to the C program that the atanh() routine is available.

d_atolf (atolf.U):
	This variable conditionally defines the HAS_ATOLF symbol, which
	indicates to the C program that the atolf() routine is available.

d_atoll (atoll.U):
	This variable conditionally defines the HAS_ATOLL symbol, which
	indicates to the C program that the atoll() routine is available.

d_attribute_always_inline (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_ALWAYS_INLINE,
	which indicates that the C compiler can know that certain
	functions should always be inlined.

d_attribute_deprecated (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_DEPRECATED, which
	indicates that GCC can handle the attribute for marking deprecated
	APIs

d_attribute_format (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_FORMAT, which
	indicates the C compiler can check for printf-like formats.

d_attribute_malloc (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_MALLOC, which
	indicates the C compiler can understand functions as having
	malloc-like semantics.

d_attribute_nonnull (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_NONNULL, which
	indicates that the C compiler can know that certain arguments
	must not be NULL, and will check accordingly at compile time.

d_attribute_noreturn (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_NORETURN, which
	indicates that the C compiler can know that certain functions
	are guaranteed never to return.

d_attribute_pure (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_PURE, which
	indicates that the C compiler can know that certain functions
	are "pure" functions, meaning that they have no side effects, and
	only rely on function input and/or global data for their results.

d_attribute_unused (d_attribut.U):
	This variable conditionally defines HASATTRIBUTE_UNUSED, which
	indicates that the C compiler can know that certain variables
	and arguments may not always be used, and to not throw warnings
	if they don't get used.

d_attribute_visibility (d_attribut.U):
	This variable conditionally defines the HASATTRIBUTE_VISIBILITY symbol,
	and indicates different GCC attribute visibility

d_attribute_warn_unused_result (d_attribut.U):
	This variable conditionally defines
	HASATTRIBUTE_WARN_UNUSED_RESULT, which indicates that the C
	compiler can know that certain functions have a return values
	that must not be ignored, such as malloc() or open().

d_backtrace (d_backtrace.U):
	This variable conditionally defines the HAS_BACKTRACE symbol, which
	indicates to the C program that the backtrace() routine is available
	to get a stack trace.

d_bsd (Guess.U):
	This symbol conditionally defines the symbol BSD when running on a
	BSD system.

d_bsdgetpgrp (d_getpgrp.U):
	This variable conditionally defines USE_BSD_GETPGRP if
	getpgrp needs one arguments whereas USG one needs none.

d_bsdsetpgrp (d_setpgrp.U):
	This variable conditionally defines USE_BSD_SETPGRP if
	setpgrp needs two arguments whereas USG one needs none.
	See also d_setpgid for a POSIX interface.

d_builtin_add_overflow (d_builtin_overflow.U):
	This variable conditionally defines HAS_BUILTIN_ADD_OVERFLOW, which
	indicates that the compiler supports __builtin_add_overflow(x,y,&z)
	for safely adding x and y into z while checking for overflow.

d_builtin_choose_expr (d_builtin.U):
	This conditionally defines HAS_BUILTIN_CHOOSE_EXPR, which
	indicates that the compiler supports __builtin_choose_expr(x,y,z).
	This built-in function is analogous to the "x?y:z" operator in C,
	except that the expression returned has its type unaltered by
	promotion rules. Also, the built-in function does not evaluate
	the expression that was not chosen.

d_builtin_expect (d_builtin.U):
	This conditionally defines HAS_BUILTIN_EXPECT, which indicates
	that the compiler supports __builtin_expect(exp,c).  You may use
	__builtin_expect to provide the compiler with branch prediction
	information.

d_builtin_mul_overflow (d_builtin_overflow.U):
	This variable conditionally defines HAS_BUILTIN_MUL_OVERFLOW, which
	indicates that the compiler supports __builtin_mul_overflow(x,y,&z)
	for safely multiplying x and y into z while checking for overflow.

d_builtin_sub_overflow (d_builtin_overflow.U):
	This variable conditionally defines HAS_BUILTIN_SUB_OVERFLOW, which
	indicates that the compiler supports __builtin_sub_overflow(x,y,&z)
	for safely subtracting y from x into z while checking for overflow.

d_c99_variadic_macros (d_c99_variadic.U):
	This variable conditionally defines the HAS_C99_VARIADIC_MACROS
	symbol, which indicates to the C program that C99 variadic macros
	are available.

d_casti32 (d_casti32.U):
	This variable conditionally defines CASTI32, which indicates
	whether the C compiler can cast large floats to 32-bit ints.

d_castneg (d_castneg.U):
	This variable conditionally defines CASTNEG, which indicates
	whether the C compiler can cast negative float to unsigned.

d_cbrt (d_cbrt.U):
	This variable conditionally defines the HAS_CBRT symbol, which
	indicates to the C program that the cbrt() (cube root) function
	is available.

d_chown (d_chown.U):
	This variable conditionally defines the HAS_CHOWN symbol, which
	indicates to the C program that the chown() routine is available.

d_chroot (d_chroot.U):
	This variable conditionally defines the HAS_CHROOT symbol, which
	indicates to the C program that the chroot() routine is available.

d_chsize (d_chsize.U):
	This variable conditionally defines the CHSIZE symbol, which
	indicates to the C program that the chsize() routine is available
	to truncate files.  You might need a -lx to get this routine.

d_class (d_class.U):
	This variable conditionally defines the HAS_CLASS symbol, which
	indicates to the C program that the class() routine is available.

d_clearenv (d_clearenv.U):
	This variable conditionally defines the HAS_CLEARENV symbol, which
	indicates to the C program that the clearenv () routine is available.

d_closedir (d_closedir.U):
	This variable conditionally defines HAS_CLOSEDIR if closedir() is
	available.

d_cmsghdr_s (d_cmsghdr_s.U):
	This variable conditionally defines the HAS_STRUCT_CMSGHDR symbol,
	which indicates that the struct cmsghdr is supported.

d_copysign (d_copysign.U):
	This variable conditionally defines the HAS_COPYSIGN symbol, which
	indicates to the C program that the copysign() routine is available.

d_copysignl (d_copysignl.U):
	This variable conditionally defines the HAS_COPYSIGNL symbol, which
	indicates to the C program that the copysignl() routine is available.
	If aintl is also present we can emulate modfl.

d_cplusplus (d_cplusplus.U):
	This variable conditionally defines the USE_CPLUSPLUS symbol, which
	indicates that a C++ compiler was used to compiled Perl and will be
	used to compile extensions.

d_crypt (d_crypt.U):
	This variable conditionally defines the CRYPT symbol, which
	indicates to the C program that the crypt() routine is available
	to encrypt passwords and the like.

d_crypt_r (d_crypt_r.U):
	This variable conditionally defines the HAS_CRYPT_R symbol,
	which indicates to the C program that the crypt_r()
	routine is available.

d_csh (d_csh.U):
	This variable conditionally defines the CSH symbol, which
	indicates to the C program that the C-shell exists.

d_ctermid (d_ctermid.U):
	This variable conditionally defines CTERMID if ctermid() is
	available to generate filename for terminal.

d_ctermid_r (d_ctermid_r.U):
	This variable conditionally defines the HAS_CTERMID_R symbol,
	which indicates to the C program that the ctermid_r()
	routine is available.

d_ctime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_CTIME64 symbol, which
	indicates to the C program that the ctime64 () routine is available.

d_ctime_r (d_ctime_r.U):
	This variable conditionally defines the HAS_CTIME_R symbol,
	which indicates to the C program that the ctime_r()
	routine is available.

d_cuserid (d_cuserid.U):
	This variable conditionally defines the HAS_CUSERID symbol, which
	indicates to the C program that the cuserid() routine is available
	to get character login names.

d_dbminitproto (d_dbminitproto.U):
	This variable conditionally defines the HAS_DBMINIT_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the dbminit() function.  Otherwise, it is
	up to the program to supply one.

d_difftime (d_difftime.U):
	This variable conditionally defines the HAS_DIFFTIME symbol, which
	indicates to the C program that the difftime() routine is available.

d_difftime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_DIFFTIME64 symbol, which
	indicates to the C program that the difftime64 () routine is available.

d_dir_dd_fd (d_dir_dd_fd.U):
	This variable conditionally defines the HAS_DIR_DD_FD symbol, which
	indicates that the DIR directory stream type contains a member
	variable called dd_fd.

d_dirfd (d_dirfd.U):
	This variable conditionally defines the HAS_DIRFD constant,
	which indicates to the C program that dirfd() is available
	to return the file descriptor of a directory stream.

d_dirnamlen (i_dirent.U):
	This variable conditionally defines DIRNAMLEN, which indicates
	to the C program that the length of directory entry names is
	provided by a d_namelen field.

d_dladdr (d_dladdr.U):
	This variable conditionally defines the HAS_DLADDR symbol, which
	indicates to the C program that the dladdr() routine is available
	to get a stack trace.

d_dlerror (d_dlerror.U):
	This variable conditionally defines the HAS_DLERROR symbol, which
	indicates to the C program that the dlerror() routine is available.

d_dlopen (d_dlopen.U):
	This variable conditionally defines the HAS_DLOPEN symbol, which
	indicates to the C program that the dlopen() routine is available.

d_dlsymun (d_dlsymun.U):
	This variable conditionally defines DLSYM_NEEDS_UNDERSCORE, which
	indicates that we need to prepend an underscore to the symbol
	name before calling dlsym().

d_dosuid (d_dosuid.U):
	This variable conditionally defines the symbol DOSUID, which
	tells the C program that it should insert setuid emulation code
	on hosts which have setuid #! scripts disabled.

d_double_has_inf (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_HAS_INF
	which indicates that the double type has an infinity.

d_double_has_nan (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_HAS_NAN
	which indicates that the double type has a not-a-number.

d_double_has_negative_zero (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_HAS_NEGATIVE_ZERO
	which indicates that the double type has a negative zero.

d_double_has_subnormals (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_HAS_SUBNORMALS
	which indicates that the double type has subnormals (denormals).

d_double_style_cray (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_STYLE_CRAY
	which indicates that the double is the 64-bit CRAY mainframe format.

d_double_style_ibm (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_STYLE_IBM,
	which indicates that the double is the 64-bit IBM mainframe format.

d_double_style_ieee (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_STYLE_IEEE,
	which indicates that the double is the 64-bit IEEE 754.

d_double_style_vax (longdblfio.U):
	This variable conditionally defines the symbol DOUBLE_STYLE_VAX,
	which indicates that the double is the 64-bit VAX format D or G.

d_drand48_r (d_drand48_r.U):
	This variable conditionally defines the HAS_DRAND48_R symbol,
	which indicates to the C program that the drand48_r()
	routine is available.

d_drand48proto (d_drand48proto.U):
	This variable conditionally defines the HAS_DRAND48_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the drand48() function.  Otherwise, it is
	up to the program to supply one.

d_dup2 (d_dup2.U):
	This variable conditionally defines HAS_DUP2 if dup2() is
	available to duplicate file descriptors.

d_dup3 (d_dup3.U):
	This variable conditionally defines HAS_DUP3 if dup3() is
	available to duplicate file descriptors.

d_duplocale (d_newlocale.U):
	This variable conditionally defines the HAS_DUPLOCALE symbol, which
	indicates to the C program that the duplocale() routine is available
	to duplicate a locale object.

d_eaccess (d_eaccess.U):
	This variable conditionally defines the HAS_EACCESS symbol, which
	indicates to the C program that the eaccess() routine is available.

d_endgrent (d_endgrent.U):
	This variable conditionally defines the HAS_ENDGRENT symbol, which
	indicates to the C program that the endgrent() routine is available
	for sequential access of the group database.

d_endgrent_r (d_endgrent_r.U):
	This variable conditionally defines the HAS_ENDGRENT_R symbol,
	which indicates to the C program that the endgrent_r()
	routine is available.

d_endhent (d_endhent.U):
	This variable conditionally defines HAS_ENDHOSTENT if endhostent() is
	available to close whatever was being used for host queries.

d_endhostent_r (d_endhostent_r.U):
	This variable conditionally defines the HAS_ENDHOSTENT_R symbol,
	which indicates to the C program that the endhostent_r()
	routine is available.

d_endnent (d_endnent.U):
	This variable conditionally defines HAS_ENDNETENT if endnetent() is
	available to close whatever was being used for network queries.

d_endnetent_r (d_endnetent_r.U):
	This variable conditionally defines the HAS_ENDNETENT_R symbol,
	which indicates to the C program that the endnetent_r()
	routine is available.

d_endpent (d_endpent.U):
	This variable conditionally defines HAS_ENDPROTOENT if endprotoent() is
	available to close whatever was being used for protocol queries.

d_endprotoent_r (d_endprotoent_r.U):
	This variable conditionally defines the HAS_ENDPROTOENT_R symbol,
	which indicates to the C program that the endprotoent_r()
	routine is available.

d_endpwent (d_endpwent.U):
	This variable conditionally defines the HAS_ENDPWENT symbol, which
	indicates to the C program that the endpwent() routine is available
	for sequential access of the passwd database.

d_endpwent_r (d_endpwent_r.U):
	This variable conditionally defines the HAS_ENDPWENT_R symbol,
	which indicates to the C program that the endpwent_r()
	routine is available.

d_endsent (d_endsent.U):
	This variable conditionally defines HAS_ENDSERVENT if endservent() is
	available to close whatever was being used for service queries.

d_endservent_r (d_endservent_r.U):
	This variable conditionally defines the HAS_ENDSERVENT_R symbol,
	which indicates to the C program that the endservent_r()
	routine is available.

d_eofnblk (nblock_io.U):
	This variable conditionally defines EOF_NONBLOCK if EOF can be seen
	when reading from a non-blocking I/O source.

d_erf (d_erf.U):
	This variable conditionally defines the HAS_ERF symbol, which
	indicates to the C program that the erf() routine is available.

d_erfc (d_erfc.U):
	This variable conditionally defines the HAS_ERFC symbol, which
	indicates to the C program that the erfc() routine is available.

d_eunice (Guess.U):
	This variable conditionally defines the symbols EUNICE and VAX, which
	alerts the C program that it must deal with idiosyncrasies of VMS.

d_exp2 (d_exp2.U):
	This variable conditionally defines the HAS_EXP2 symbol, which
	indicates to the C program that the exp2() routine is available.

d_expm1 (d_expm1.U):
	This variable conditionally defines the HAS_EXPM1 symbol, which
	indicates to the C program that the expm1() routine is available.

d_faststdio (d_faststdio.U):
	This variable conditionally defines the HAS_FAST_STDIO symbol,
	which indicates to the C program that the "fast stdio" is available
	to manipulate the stdio buffers directly.

d_fchdir (d_fchdir.U):
	This variable conditionally defines the HAS_FCHDIR symbol, which
	indicates to the C program that the fchdir() routine is available.

d_fchmod (d_fchmod.U):
	This variable conditionally defines the HAS_FCHMOD symbol, which
	indicates to the C program that the fchmod() routine is available
	to change mode of opened files.

d_fchmodat (d_fsat.U):
	This variable conditionally defines the HAS_FCHMODAT symbol, which
	indicates the POSIX fchmodat() function is available.

d_fchown (d_fchown.U):
	This variable conditionally defines the HAS_FCHOWN symbol, which
	indicates to the C program that the fchown() routine is available
	to change ownership of opened files.

d_fcntl (d_fcntl.U):
	This variable conditionally defines the HAS_FCNTL symbol, and indicates
	whether the fcntl() function exists

d_fcntl_can_lock (d_fcntl_can_lock.U):
	This variable conditionally defines the FCNTL_CAN_LOCK symbol
	and indicates whether file locking with fcntl() works.

d_fd_macros (d_fd_set.U):
	This variable contains the eventual value of the HAS_FD_MACROS symbol,
	which indicates if your C compiler knows about the macros which
	manipulate an fd_set.

d_fd_set (d_fd_set.U):
	This variable contains the eventual value of the HAS_FD_SET symbol,
	which indicates if your C compiler knows about the fd_set typedef.

d_fdclose (d_fdclose.U):
	This variable conditionally defines the HAS_FDCLOSE symbol, which
	indicates to the C program that the fdclose() routine is available.

d_fdim (d_fdim.U):
	This variable conditionally defines the HAS_FDIM symbol, which
	indicates to the C program that the fdim() routine is available.

d_fds_bits (d_fd_set.U):
	This variable contains the eventual value of the HAS_FDS_BITS symbol,
	which indicates if your fd_set typedef contains the fds_bits member.
	If you have an fd_set typedef, but the dweebs who installed it did
	a half-fast job and neglected to provide the macros to manipulate
	an fd_set, HAS_FDS_BITS will let us know how to fix the gaffe.

d_fegetround (d_fegetround.U):
	This variable conditionally defines HAS_FEGETROUND if fegetround() is
	available to get the floating point rounding mode.

d_ffs (d_ffs.U):
	This variable conditionally defines the HAS_FFS symbol, which
	indicates to the C program that the ffs() routine is available
	to find the first bit which is set in its integer argument.

d_ffsl (d_ffs.U):
	This variable conditionally defines the HAS_FFSL symbol, which
	indicates to the C program that the ffsl() routine is available
	to find the first bit which is set in its long integer argument.

d_fgetpos (d_fgetpos.U):
	This variable conditionally defines HAS_FGETPOS if fgetpos() is
	available to get the file position indicator.

d_finite (d_finite.U):
	This variable conditionally defines the HAS_FINITE symbol, which
	indicates to the C program that the finite() routine is available.

d_finitel (d_finitel.U):
	This variable conditionally defines the HAS_FINITEL symbol, which
	indicates to the C program that the finitel() routine is available.

d_flexfnam (d_flexfnam.U):
	This variable conditionally defines the FLEXFILENAMES symbol, which
	indicates that the system supports filenames longer than 14 characters.

d_flock (d_flock.U):
	This variable conditionally defines HAS_FLOCK if flock() is
	available to do file locking.

d_flockproto (d_flockproto.U):
	This variable conditionally defines the HAS_FLOCK_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the flock() function.  Otherwise, it is
	up to the program to supply one.

d_fma (d_fma.U):
	This variable conditionally defines the HAS_FMA symbol, which
	indicates to the C program that the fma() routine is available.

d_fmax (d_fmax.U):
	This variable conditionally defines the HAS_FMAX symbol, which
	indicates to the C program that the fmax() routine is available.

d_fmin (d_fmin.U):
	This variable conditionally defines the HAS_FMIN symbol, which
	indicates to the C program that the fmin() routine is available.

d_fdopendir (d_fdopendir.U):
	This variable conditionally defines the HAS_FORK symbol, which
	indicates that the fdopen routine is available to open a
	directory descriptor.

d_fork (d_fork.U):
	This variable conditionally defines the HAS_FORK symbol, which
	indicates to the C program that the fork() routine is available.

d_fp_class (d_fp_class.U):
	This variable conditionally defines the HAS_FP_CLASS symbol, which
	indicates to the C program that the fp_class() routine is available.

d_fp_classify (d_fpclassify.U):
	This variable conditionally defines the HAS_FP_CLASSIFY symbol, which
	indicates to the C program that the fp_classify() routine is available.

d_fp_classl (d_fp_classl.U):
	This variable conditionally defines the HAS_FP_CLASSL symbol, which
	indicates to the C program that the fp_classl() routine is available.

d_fpathconf (d_pathconf.U):
	This variable conditionally defines the HAS_FPATHCONF symbol, which
	indicates to the C program that the pathconf() routine is available
	to determine file-system related limits and options associated
	with a given open file descriptor.

d_fpclass (d_fpclass.U):
	This variable conditionally defines the HAS_FPCLASS symbol, which
	indicates to the C program that the fpclass() routine is available.

d_fpclassify (d_fpclassify.U):
	This variable conditionally defines the HAS_FPCLASSIFY symbol, which
	indicates to the C program that the fpclassify() routine is available.

d_fpclassl (d_fpclassl.U):
	This variable conditionally defines the HAS_FPCLASSL symbol, which
	indicates to the C program that the fpclassl() routine is available.

d_fpgetround (d_fpgetround.U):
	This variable conditionally defines HAS_FPGETROUND if fpgetround()
	is available to get the floating point rounding mode.

d_fpos64_t (d_fpos64_t.U):
	This symbol will be defined if the C compiler supports fpos64_t.

d_freelocale (d_newlocale.U):
	This variable conditionally defines the HAS_FREELOCALE symbol, which
	indicates to the C program that the freelocale() routine is available
	to deallocates the resources associated with a locale object.

d_frexpl (d_frexpl.U):
	This variable conditionally defines the HAS_FREXPL symbol, which
	indicates to the C program that the frexpl() routine is available.

d_fs_data_s (d_fs_data_s.U):
	This variable conditionally defines the HAS_STRUCT_FS_DATA symbol,
	which indicates that the struct fs_data is supported.

d_fseeko (d_fseeko.U):
	This variable conditionally defines the HAS_FSEEKO symbol, which
	indicates to the C program that the fseeko() routine is available.

d_fsetpos (d_fsetpos.U):
	This variable conditionally defines HAS_FSETPOS if fsetpos() is
	available to set the file position indicator.

d_fstatfs (d_fstatfs.U):
	This variable conditionally defines the HAS_FSTATFS symbol, which
	indicates to the C program that the fstatfs() routine is available.

d_fstatvfs (d_statvfs.U):
	This variable conditionally defines the HAS_FSTATVFS symbol, which
	indicates to the C program that the fstatvfs() routine is available.

d_fsync (d_fsync.U):
	This variable conditionally defines the HAS_FSYNC symbol, which
	indicates to the C program that the fsync() routine is available.

d_ftello (d_ftello.U):
	This variable conditionally defines the HAS_FTELLO symbol, which
	indicates to the C program that the ftello() routine is available.

d_ftime (d_ftime.U):
	This variable conditionally defines the HAS_FTIME symbol, which indicates
	that the ftime() routine exists.  The ftime() routine is basically
	a sub-second accuracy clock.

d_futimes (d_futimes.U):
	This variable conditionally defines the HAS_FUTIMES symbol, which
	indicates to the C program that the futimes() routine is available.

d_gai_strerror (d_gai_strerror.U):
	This variable conditionally defines the HAS_GAI_STRERROR symbol
	if the gai_strerror() routine is available and can be used to
	translate error codes returned by getaddrinfo() into human
	readable strings.

d_Gconvert (d_gconvert.U):
	This variable holds what Gconvert is defined as to convert
	floating point numbers into strings.  By default, Configure
	sets this macro to use the first of gconvert, gcvt, or sprintf
	that pass sprintf-%g-like behavior tests.  If perl is using
	long doubles, the macro uses the first of the following
	functions that pass Configure's tests: qgcvt, sprintf (if
	Configure knows how to make sprintf format long doubles--see
	sPRIgldbl), gconvert, gcvt, and sprintf (casting to double).
	The gconvert_preference and gconvert_ld_preference variables
	can be used to alter Configure's preferences, for doubles and
	long doubles, respectively.  If present, they contain a
	space-separated list of one or more of the above function
	names in the order they should be tried.

	d_Gconvert may be set to override Configure with a platform-
	specific function.  If this function expects a double, a
	different value may need to be set by the uselongdouble.cbu
	call-back unit so that long doubles can be formatted without
	loss of precision.

d_gdbm_ndbm_h_uses_prototypes (i_ndbm.U):
	This variable conditionally defines the NDBM_H_USES_PROTOTYPES symbol,
	which indicates that the gdbm-ndbm.h include file uses real ANSI C
	prototypes instead of K&R style function declarations. K&R style
	declarations are unsupported in C++, so the include file requires
	special handling when using a C++ compiler and this variable is
	undefined. Consult the different d_*ndbm_h_uses_prototypes variables
	to get the same information for alternative ndbm.h include files.

d_gdbmndbm_h_uses_prototypes (i_ndbm.U):
	This variable conditionally defines the NDBM_H_USES_PROTOTYPES symbol,
	which indicates that the gdbm/ndbm.h include file uses real ANSI C
	prototypes instead of K&R style function declarations. K&R style
	declarations are unsupported in C++, so the include file requires
	special handling when using a C++ compiler and this variable is
	undefined. Consult the different d_*ndbm_h_uses_prototypes variables
	to get the same information for alternative ndbm.h include files.

d_getaddrinfo (d_getaddrinfo.U):
	This variable conditionally defines the HAS_GETADDRINFO symbol,
	which indicates to the C program that the getaddrinfo() function
	is available.

d_getcwd (d_getcwd.U):
	This variable conditionally defines the HAS_GETCWD symbol, which
	indicates to the C program that the getcwd() routine is available
	to get the current working directory.

d_getenv_preserves_other_thread (d_getenv_thread.U):
	This variable conditionally defines the GETENV_PRESERVES_OTHER_THREAD
	symbol, which indicates to the C program that the getenv() system call
	does not zap the static buffer in a different thread.

d_getespwnam (d_getespwnam.U):
	This variable conditionally defines HAS_GETESPWNAM if getespwnam() is
	available to retrieve enhanced (shadow) password entries by name.

d_getfsstat (d_getfsstat.U):
	This variable conditionally defines the HAS_GETFSSTAT symbol, which
	indicates to the C program that the getfsstat() routine is available.

d_getgrent (d_getgrent.U):
	This variable conditionally defines the HAS_GETGRENT symbol, which
	indicates to the C program that the getgrent() routine is available
	for sequential access of the group database.

d_getgrent_r (d_getgrent_r.U):
	This variable conditionally defines the HAS_GETGRENT_R symbol,
	which indicates to the C program that the getgrent_r()
	routine is available.

d_getgrgid_r (d_getgrgid_r.U):
	This variable conditionally defines the HAS_GETGRGID_R symbol,
	which indicates to the C program that the getgrgid_r()
	routine is available.

d_getgrnam_r (d_getgrnam_r.U):
	This variable conditionally defines the HAS_GETGRNAM_R symbol,
	which indicates to the C program that the getgrnam_r()
	routine is available.

d_getgrps (d_getgrps.U):
	This variable conditionally defines the HAS_GETGROUPS symbol, which
	indicates to the C program that the getgroups() routine is available
	to get the list of process groups.

d_gethbyaddr (d_gethbyad.U):
	This variable conditionally defines the HAS_GETHOSTBYADDR symbol, which
	indicates to the C program that the gethostbyaddr() routine is available
	to look up hosts by their IP addresses.

d_gethbyname (d_gethbynm.U):
	This variable conditionally defines the HAS_GETHOSTBYNAME symbol, which
	indicates to the C program that the gethostbyname() routine is available
	to look up host names in some data base or other.

d_gethent (d_gethent.U):
	This variable conditionally defines HAS_GETHOSTENT if gethostent() is
	available to look up host names in some data base or another.

d_gethname (d_gethname.U):
	This variable conditionally defines the HAS_GETHOSTNAME symbol, which
	indicates to the C program that the gethostname() routine may be
	used to derive the host name.

d_gethostbyaddr_r (d_gethostbyaddr_r.U):
	This variable conditionally defines the HAS_GETHOSTBYADDR_R symbol,
	which indicates to the C program that the gethostbyaddr_r()
	routine is available.

d_gethostbyname_r (d_gethostbyname_r.U):
	This variable conditionally defines the HAS_GETHOSTBYNAME_R symbol,
	which indicates to the C program that the gethostbyname_r()
	routine is available.

d_gethostent_r (d_gethostent_r.U):
	This variable conditionally defines the HAS_GETHOSTENT_R symbol,
	which indicates to the C program that the gethostent_r()
	routine is available.

d_gethostprotos (d_gethostprotos.U):
	This variable conditionally defines the HAS_GETHOST_PROTOS symbol,
	which indicates to the C program that <netdb.h> supplies
	prototypes for the various gethost*() functions.
	See also netdbtype.U for probing for various netdb types.

d_getitimer (d_getitimer.U):
	This variable conditionally defines the HAS_GETITIMER symbol, which
	indicates to the C program that the getitimer() routine is available.

d_getlogin (d_getlogin.U):
	This variable conditionally defines the HAS_GETLOGIN symbol, which
	indicates to the C program that the getlogin() routine is available
	to get the login name.

d_getlogin_r (d_getlogin_r.U):
	This variable conditionally defines the HAS_GETLOGIN_R symbol,
	which indicates to the C program that the getlogin_r()
	routine is available.

d_getmnt (d_getmnt.U):
	This variable conditionally defines the HAS_GETMNT symbol, which
	indicates to the C program that the getmnt() routine is available
	to retrieve one or more mount info blocks by filename.

d_getmntent (d_getmntent.U):
	This variable conditionally defines the HAS_GETMNTENT symbol, which
	indicates to the C program that the getmntent() routine is available
	to iterate through mounted files to get their mount info.

d_getnameinfo (d_getnameinfo.U):
	This variable conditionally defines the HAS_GETNAMEINFO symbol,
	which indicates to the C program that the getnameinfo() function
	is available.

d_getnbyaddr (d_getnbyad.U):
	This variable conditionally defines the HAS_GETNETBYADDR symbol, which
	indicates to the C program that the getnetbyaddr() routine is available
	to look up networks by their IP addresses.

d_getnbyname (d_getnbynm.U):
	This variable conditionally defines the HAS_GETNETBYNAME symbol, which
	indicates to the C program that the getnetbyname() routine is available
	to look up networks by their names.

d_getnent (d_getnent.U):
	This variable conditionally defines HAS_GETNETENT if getnetent() is
	available to look up network names in some data base or another.

d_getnetbyaddr_r (d_getnetbyaddr_r.U):
	This variable conditionally defines the HAS_GETNETBYADDR_R symbol,
	which indicates to the C program that the getnetbyaddr_r()
	routine is available.

d_getnetbyname_r (d_getnetbyname_r.U):
	This variable conditionally defines the HAS_GETNETBYNAME_R symbol,
	which indicates to the C program that the getnetbyname_r()
	routine is available.

d_getnetent_r (d_getnetent_r.U):
	This variable conditionally defines the HAS_GETNETENT_R symbol,
	which indicates to the C program that the getnetent_r()
	routine is available.

d_getnetprotos (d_getnetprotos.U):
	This variable conditionally defines the HAS_GETNET_PROTOS symbol,
	which indicates to the C program that <netdb.h> supplies
	prototypes for the various getnet*() functions.
	See also netdbtype.U for probing for various netdb types.

d_getpagsz (d_getpagsz.U):
	This variable conditionally defines HAS_GETPAGESIZE if getpagesize()
	is available to get the system page size.

d_getpbyname (d_getprotby.U):
	This variable conditionally defines the HAS_GETPROTOBYNAME
	symbol, which indicates to the C program that the
	getprotobyname() routine is available to look up protocols
	by their name.

d_getpbynumber (d_getprotby.U):
	This variable conditionally defines the HAS_GETPROTOBYNUMBER
	symbol, which indicates to the C program that the
	getprotobynumber() routine is available to look up protocols
	by their number.

d_getpent (d_getpent.U):
	This variable conditionally defines HAS_GETPROTOENT if getprotoent() is
	available to look up protocols in some data base or another.

d_getpgid (d_getpgid.U):
	This variable conditionally defines the HAS_GETPGID symbol, which
	indicates to the C program that the getpgid(pid) function
	is available to get the process group id.

d_getpgrp (d_getpgrp.U):
	This variable conditionally defines HAS_GETPGRP if getpgrp() is
	available to get the current process group.

d_getpgrp2 (d_getpgrp2.U):
	This variable conditionally defines the HAS_GETPGRP2 symbol, which
	indicates to the C program that the getpgrp2() (as in DG/UX) routine
	is available to get the current process group.

d_getppid (d_getppid.U):
	This variable conditionally defines the HAS_GETPPID symbol, which
	indicates to the C program that the getppid() routine is available
	to get the parent process ID.

d_getprior (d_getprior.U):
	This variable conditionally defines HAS_GETPRIORITY if getpriority()
	is available to get a process's priority.

d_getprotobyname_r (d_getprotobyname_r.U):
	This variable conditionally defines the HAS_GETPROTOBYNAME_R symbol,
	which indicates to the C program that the getprotobyname_r()
	routine is available.

d_getprotobynumber_r (d_getprotobynumber_r.U):
	This variable conditionally defines the HAS_GETPROTOBYNUMBER_R symbol,
	which indicates to the C program that the getprotobynumber_r()
	routine is available.

d_getprotoent_r (d_getprotoent_r.U):
	This variable conditionally defines the HAS_GETPROTOENT_R symbol,
	which indicates to the C program that the getprotoent_r()
	routine is available.

d_getprotoprotos (d_getprotoprotos.U):
	This variable conditionally defines the HAS_GETPROTO_PROTOS symbol,
	which indicates to the C program that <netdb.h> supplies
	prototypes for the various getproto*() functions.
	See also netdbtype.U for probing for various netdb types.

d_getprpwnam (d_getprpwnam.U):
	This variable conditionally defines HAS_GETPRPWNAM if getprpwnam() is
	available to retrieve protected (shadow) password entries by name.

d_getpwent (d_getpwent.U):
	This variable conditionally defines the HAS_GETPWENT symbol, which
	indicates to the C program that the getpwent() routine is available
	for sequential access of the passwd database.

d_getpwent_r (d_getpwent_r.U):
	This variable conditionally defines the HAS_GETPWENT_R symbol,
	which indicates to the C program that the getpwent_r()
	routine is available.

d_getpwnam_r (d_getpwnam_r.U):
	This variable conditionally defines the HAS_GETPWNAM_R symbol,
	which indicates to the C program that the getpwnam_r()
	routine is available.

d_getpwuid_r (d_getpwuid_r.U):
	This variable conditionally defines the HAS_GETPWUID_R symbol,
	which indicates to the C program that the getpwuid_r()
	routine is available.

d_getsbyname (d_getsrvby.U):
	This variable conditionally defines the HAS_GETSERVBYNAME
	symbol, which indicates to the C program that the
	getservbyname() routine is available to look up services
	by their name.

d_getsbyport (d_getsrvby.U):
	This variable conditionally defines the HAS_GETSERVBYPORT
	symbol, which indicates to the C program that the
	getservbyport() routine is available to look up services
	by their port.

d_getsent (d_getsent.U):
	This variable conditionally defines HAS_GETSERVENT if getservent() is
	available to look up network services in some data base or another.

d_getservbyname_r (d_getservbyname_r.U):
	This variable conditionally defines the HAS_GETSERVBYNAME_R symbol,
	which indicates to the C program that the getservbyname_r()
	routine is available.

d_getservbyport_r (d_getservbyport_r.U):
	This variable conditionally defines the HAS_GETSERVBYPORT_R symbol,
	which indicates to the C program that the getservbyport_r()
	routine is available.

d_getservent_r (d_getservent_r.U):
	This variable conditionally defines the HAS_GETSERVENT_R symbol,
	which indicates to the C program that the getservent_r()
	routine is available.

d_getservprotos (d_getservprotos.U):
	This variable conditionally defines the HAS_GETSERV_PROTOS symbol,
	which indicates to the C program that <netdb.h> supplies
	prototypes for the various getserv*() functions.
	See also netdbtype.U for probing for various netdb types.

d_getspnam (d_getspnam.U):
	This variable conditionally defines HAS_GETSPNAM if getspnam() is
	available to retrieve SysV shadow password entries by name.

d_getspnam_r (d_getspnam_r.U):
	This variable conditionally defines the HAS_GETSPNAM_R symbol,
	which indicates to the C program that the getspnam_r()
	routine is available.

d_gettimeod (d_ftime.U):
	This variable conditionally defines the HAS_GETTIMEOFDAY symbol, which
	indicates that the gettimeofday() system call exists (to obtain a
	sub-second accuracy clock). You should probably include <sys/resource.h>.

d_gmtime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_GMTIME64 symbol, which
	indicates to the C program that the gmtime64 () routine is available.

d_gmtime_r (d_gmtime_r.U):
	This variable conditionally defines the HAS_GMTIME_R symbol,
	which indicates to the C program that the gmtime_r()
	routine is available.

d_gnulibc (d_gnulibc.U):
	Defined if we're dealing with the GNU C Library.

d_grpasswd (i_grp.U):
	This variable conditionally defines GRPASSWD, which indicates
	that struct group in <grp.h> contains gr_passwd.

d_has_C_UTF8 (d_setlocale.U):
	This variable is set to either "true" or "false" depending on
	whether the compilation system supports the C.UTF-8 locale.

d_hasmntopt (d_hasmntopt.U):
	This variable conditionally defines the HAS_HASMNTOPT symbol, which
	indicates to the C program that the hasmntopt() routine is available
	to query the mount options of file systems.

d_htonl (d_htonl.U):
	This variable conditionally defines HAS_HTONL if htonl() and its
	friends are available to do network order byte swapping.

d_hypot (d_hypot.U):
	This variable conditionally defines HAS_HYPOT if hypot is available
	for numerically stable hypotenuse function.

d_ilogb (d_ilogb.U):
	This variable conditionally defines the HAS_ILOGB symbol, which
	indicates to the C program that the ilogb() routine is available
	for extracting the exponent of double x as a signed integer.

d_ilogbl (d_ilogbl.U):
	This variable conditionally defines the HAS_ILOGBL symbol, which
	indicates to the C program that the ilogbl() routine is available
	for extracting the exponent of long double x as a signed integer.
	If scalbnl is also present we can emulate frexpl.

d_inc_version_list (inc_version_list.U):
	This variable conditionally defines PERL_INC_VERSION_LIST.
	It is set to undef when PERL_INC_VERSION_LIST is empty.

d_inetaton (d_inetaton.U):
	This variable conditionally defines the HAS_INET_ATON symbol, which
	indicates to the C program that the inet_aton() function is available
	to parse IP address "dotted-quad" strings.

d_inetntop (d_inetntop.U):
	This variable conditionally defines the HAS_INETNTOP symbol,
	which indicates to the C program that the inet_ntop() function
	is available.

d_inetpton (d_inetpton.U):
	This variable conditionally defines the HAS_INETPTON symbol,
	which indicates to the C program that the inet_pton() function
	is available.

d_int64_t (d_int64_t.U):
	This symbol will be defined if the C compiler supports int64_t.

d_ip_mreq (d_socket.U):
	This variable conditionally defines the HAS_IP_MREQ symbol, which
	indicates the availability of a struct ip_mreq.

d_ip_mreq_source (d_socket.U):
	This variable conditionally defines the HAS_IP_MREQ_SOURCE symbol,
	which indicates the availability of a struct ip_mreq_source.

d_ipv6_mreq (d_socket.U):
	This variable conditionally defines the HAS_IPV6_MREQ symbol, which
	indicates the availability of a struct ipv6_mreq.

d_ipv6_mreq_source (d_socket.U):
	This variable conditionally defines the HAS_IPV6_MREQ_SOURCE symbol,
	which indicates the availability of a struct ipv6_mreq_source.

d_isascii (d_isascii.U):
	This variable conditionally defines the HAS_ISASCII constant,
	which indicates to the C program that isascii() is available.

d_isblank (d_isblank.U):
	This variable conditionally defines the HAS_ISBLANK constant,
	which indicates to the C program that isblank() is available.

d_isfinite (d_isfinite.U):
	This variable conditionally defines the HAS_ISFINITE symbol, which
	indicates to the C program that the isfinite() routine is available.

d_isfinitel (d_isfinitel.U):
	This variable conditionally defines the HAS_ISFINITEL symbol, which
	indicates to the C program that the isfinitel() routine is available.

d_isinf (d_isinf.U):
	This variable conditionally defines the HAS_ISINF symbol, which
	indicates to the C program that the isinf() routine is available.

d_isinfl (d_isinfl.U):
	This variable conditionally defines the HAS_ISINFL symbol, which
	indicates to the C program that the isinfl() routine is available.

d_isless (d_isless.U):
	This variable conditionally defines the HAS_ISLESS symbol, which
	indicates to the C program that the isless() routine is available.

d_isnan (d_isnan.U):
	This variable conditionally defines the HAS_ISNAN symbol, which
	indicates to the C program that the isnan() routine is available.

d_isnanl (d_isnanl.U):
	This variable conditionally defines the HAS_ISNANL symbol, which
	indicates to the C program that the isnanl() routine is available.

d_isnormal (d_isnormal.U):
	This variable conditionally defines the HAS_ISNORMAL symbol, which
	indicates to the C program that the isnormal() routine is available.

d_j0 (d_j0.U):
	This variable conditionally defines the HAS_J0 symbol, which
	indicates to the C program that the j0() routine is available.

d_j0l (d_j0.U):
	This variable conditionally defines the HAS_J0L symbol, which
	indicates to the C program that the j0l() routine is available.

d_killpg (d_killpg.U):
	This variable conditionally defines the HAS_KILLPG symbol, which
	indicates to the C program that the killpg() routine is available
	to kill process groups.

d_lc_monetary_2008 (d_lc_monetary_2008.U):
	This variable conditionally defines HAS_LC_MONETARY_2008 if libc
	has the international currency locale rules from POSIX
	1003.1-2008.

d_lchown (d_lchown.U):
	This variable conditionally defines the HAS_LCHOWN symbol, which
	indicates to the C program that the lchown() routine is available
	to operate on a symbolic link (instead of following the link).

d_ldbl_dig (d_ldbl_dig.U):
	This variable conditionally defines d_ldbl_dig if this system's
	header files provide LDBL_DIG, which is the number of significant
	digits in a long double precision number.

d_ldexpl (d_longdbl.U):
	This variable conditionally defines the HAS_LDEXPL symbol, which
	indicates to the C program that the ldexpl() routine is available.

d_lgamma (d_lgamma.U):
	This variable conditionally defines the HAS_LGAMMA symbol, which
	indicates to the C program that the lgamma() routine is available
	for the log gamma function.  See also d_tgamma and d_lgamma_r.

d_lgamma_r (d_lgamma_r.U):
	This variable conditionally defines the HAS_LGAMMA_R symbol, which
	indicates to the C program that the lgamma_r() routine is available
	for the log gamma function, without using the global signgam variable.

d_libm_lib_version (d_libm_lib_version.U):
	This variable conditionally defines the LIBM_LIB_VERSION symbol,
	which indicates to the C program that math.h defines _LIB_VERSION
	being available in libm

d_libname_unique (so.U):
	This variable is defined if the target system insists on unique
	basenames for shared library files. This is currently true on Android,
	false everywhere else we know of.
	Defaults to 'undef'.

d_link (d_link.U):
	This variable conditionally defines HAS_LINK if link() is
	available to create hard links.

d_linkat (d_fsat.U):
	This variable conditionally defines the HAS_LINKAT symbol, which
	indicates the POSIX linkat() function is available.

d_llrint (d_llrint.U):
	This variable conditionally defines the HAS_LLRINT symbol, which
	indicates to the C program that the llrint() routine is available
	to return the long long value closest to a double (according
	to the current rounding mode).

d_llrintl (d_llrintl.U):
	This variable conditionally defines the HAS_LLRINTL symbol, which
	indicates to the C program that the llrintl() routine is available
	to return the long long value closest to a long double (according
	to the current rounding mode).

d_llround (d_llround.U):
	This variable conditionally defines the HAS_LLROUND symbol, which
	indicates to the C program that the llround() routine is available
	to return the long long value nearest to x.

d_llroundl (d_llroundl.U):
	This variable conditionally defines the HAS_LLROUNDL symbol, which
	indicates to the C program that the llroundl() routine is available
	to return the long long value nearest to x away from zero.

d_localeconv_l (d_localeconv_l.U):
	This variable conditionally defines the HAS_LOCALECONV_L symbol, which
	indicates to the C program that the localeconv_l() routine is available.

d_localtime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_LOCALTIME64 symbol, which
	indicates to the C program that the localtime64 () routine is available.

d_localtime_r (d_localtime_r.U):
	This variable conditionally defines the HAS_LOCALTIME_R symbol,
	which indicates to the C program that the localtime_r()
	routine is available.

d_localtime_r_needs_tzset (d_localtime_r.U):
	This variable conditionally defines the LOCALTIME_R_NEEDS_TZSET
	symbol, which makes us call tzset before localtime_r()

d_locconv (d_locconv.U):
	This variable conditionally defines HAS_LOCALECONV if localeconv() is
	available for numeric and monetary formatting conventions.

d_lockf (d_lockf.U):
	This variable conditionally defines HAS_LOCKF if lockf() is
	available to do file locking.

d_log1p (d_log1p.U):
	This variable conditionally defines the HAS_LOG1P symbol, which
	indicates to the C program that the logp1() routine is available
	to compute log(1 + x) for values of x close to zero.

d_log2 (d_log2.U):
	This variable conditionally defines the HAS_LOG2 symbol, which
	indicates to the C program that the log2() routine is available
	to compute log base two.

d_logb (d_logb.U):
	This variable conditionally defines the HAS_LOGB symbol, which
	indicates to the C program that the logb() routine is available
	to extract the exponent of x.

d_long_double_style_ieee (d_longdbl.U):
	This variable conditionally defines LONG_DOUBLE_STYLE_IEEE
	if the long double is any of the IEEE 754 style long doubles:
	LONG_DOUBLE_STYLE_IEEE_STD, LONG_DOUBLE_STYLE_IEEE_EXTENDED,
	LONG_DOUBLE_STYLE_IEEE_DOUBLEDOUBLE.

d_long_double_style_ieee_doubledouble (d_longdbl.U):
	This variable conditionally defines LONG_DOUBLE_STYLE_IEEE_DOUBLEDOUBLE
	if the long double is the 128-bit IEEE 754 double-double.

d_long_double_style_ieee_extended (d_longdbl.U):
	This variable conditionally defines LONG_DOUBLE_STYLE_IEEE_EXTENDED
	if the long double is the 80-bit IEEE 754 extended precision.
	Note that despite the 'extended' this is less than the 'std',
	since this is an extension of the double precision.

d_long_double_style_ieee_std (d_longdbl.U):
	This variable conditionally defines LONG_DOUBLE_STYLE_IEEE_STD
	if the long double is the 128-bit IEEE 754.

d_long_double_style_vax (d_longdbl.U):
	This variable conditionally defines LONG_DOUBLE_STYLE_VAX
	if the long double is the 128-bit VAX format H.

d_longdbl (d_longdbl.U):
	This variable conditionally defines HAS_LONG_DOUBLE if
	the long double type is supported.

d_longlong (d_longlong.U):
	This variable conditionally defines HAS_LONG_LONG if
	the long long type is supported.

d_lrint (d_lrint.U):
	This variable conditionally defines the HAS_LRINT symbol, which
	indicates to the C program that the lrint() routine is available
	to return the integral value closest to a double (according
	to the current rounding mode).

d_lrintl (d_lrintl.U):
	This variable conditionally defines the HAS_LRINTL symbol, which
	indicates to the C program that the lrintl() routine is available
	to return the integral value closest to a long double (according
	to the current rounding mode).

d_lround (d_lround.U):
	This variable conditionally defines the HAS_LROUND symbol, which
	indicates to the C program that the lround() routine is available
	to return the integral value nearest to x.

d_lroundl (d_lroundl.U):
	This variable conditionally defines the HAS_LROUNDL symbol, which
	indicates to the C program that the lroundl() routine is available
	to return the integral value nearest to x away from zero.

d_lseekproto (d_lseekproto.U):
	This variable conditionally defines the HAS_LSEEK_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the lseek() function.  Otherwise, it is
	up to the program to supply one.

d_lstat (d_lstat.U):
	This variable conditionally defines HAS_LSTAT if lstat() is
	available to do file stats on symbolic links.

d_madvise (d_madvise.U):
	This variable conditionally defines HAS_MADVISE if madvise() is
	available to map a file into memory.

d_malloc_good_size (d_malloc_size.U):
	This symbol, if defined, indicates that the malloc_good_size
	routine is available for use.

d_malloc_size (d_malloc_size.U):
	This symbol, if defined, indicates that the malloc_size
	routine is available for use.

d_malloc_usable_size (d_malloc_size.U):
	This symbol, if defined, indicates that the malloc_usable_size
	routine is available for use.

d_mblen (d_mblen.U):
	This variable conditionally defines the HAS_MBLEN symbol, which
	indicates to the C program that the mblen() routine is available
	to find the number of bytes in a multibyte character.

d_mbrlen (d_mbrlen.U):
	This variable conditionally defines the HAS_MBRLEN symbol if the
	mbrlen() routine is available to be used to get the length of
	multi-byte character strings.

d_mbrtowc (d_mbrtowc.U):
	This variable conditionally defines the HAS_MBRTOWC symbol if the
	mbrtowc() routine is available to be used to convert a multi-byte
	character into a wide character.

d_mbstowcs (d_mbstowcs.U):
	This variable conditionally defines the HAS_MBSTOWCS symbol, which
	indicates to the C program that the mbstowcs() routine is available
	to convert a multibyte string into a wide character string.

d_mbtowc (d_mbtowc.U):
	This variable conditionally defines the HAS_MBTOWC symbol, which
	indicates to the C program that the mbtowc() routine is available
	to convert multibyte to a wide character.

d_memmem (d_memmem.U):
	This variable conditionally defines the HAS_MEMMEM symbol, which
	indicates to the C program that the memmem() routine is available
	to return a pointer to the start of the first occurrence of a
	substring in a memory area (or NULL if not found).

d_memrchr (d_memrchr.U):
	This variable conditionally defines the HAS_MEMRCHR symbol, which
	indicates to the C program that the memrchr() routine is available
	to return a pointer to the last occurrence of a byte in a memory
	area (or NULL if not found).

d_mkdir (d_mkdir.U):
	This variable conditionally defines the HAS_MKDIR symbol, which
	indicates to the C program that the mkdir() routine is available
	to create directories..

d_mkdtemp (d_mkdtemp.U):
	This variable conditionally defines the HAS_MKDTEMP symbol, which
	indicates to the C program that the mkdtemp() routine is available
	to exclusively create a uniquely named temporary directory.

d_mkfifo (d_mkfifo.U):
	This variable conditionally defines the HAS_MKFIFO symbol, which
	indicates to the C program that the mkfifo() routine is available.

d_mkostemp (d_mkostemp.U):
	This variable conditionally defines HAS_MKOSTEMP if mkostemp() is
	available to exclusively create and open a uniquely named (with a
	suffix) temporary file.

d_mkstemp (d_mkstemp.U):
	This variable conditionally defines the HAS_MKSTEMP symbol, which
	indicates to the C program that the mkstemp() routine is available
	to exclusively create and open a uniquely named temporary file.

d_mkstemps (d_mkstemps.U):
	This variable conditionally defines the HAS_MKSTEMPS symbol, which
	indicates to the C program that the mkstemps() routine is available
	to exclusively create and open a uniquely named (with a suffix)
	temporary file.

d_mktime (d_mktime.U):
	This variable conditionally defines the HAS_MKTIME symbol, which
	indicates to the C program that the mktime() routine is available.

d_mktime64 (d_timefuncs64.U):
	This variable conditionally defines the HAS_MKTIME64 symbol, which
	indicates to the C program that the mktime64 () routine is available.

d_mmap (d_mmap.U):
	This variable conditionally defines HAS_MMAP if mmap() is
	available to map a file into memory.

d_modfl (d_modfl.U):
	This variable conditionally defines the HAS_MODFL symbol, which
	indicates to the C program that the modfl() routine is available.

d_modflproto (d_modfl.U):
	This symbol, if defined, indicates that the system provides
	a prototype for the modfl() function.  Otherwise, it is up
	to the program to supply one.  C99 says it should be
	long double modfl(long double, long double *);

d_mprotect (d_mprotect.U):
	This variable conditionally defines HAS_MPROTECT if mprotect() is
	available to modify the access protection of a memory mapped file.

d_msg (d_msg.U):
	This variable conditionally defines the HAS_MSG symbol, which
	indicates that the entire msg*(2) library is present.

d_msg_ctrunc (d_socket.U):
	This variable conditionally defines the HAS_MSG_CTRUNC symbol,
	which indicates that the MSG_CTRUNC is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_msg_dontroute (d_socket.U):
	This variable conditionally defines the HAS_MSG_DONTROUTE symbol,
	which indicates that the MSG_DONTROUTE is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_msg_oob (d_socket.U):
	This variable conditionally defines the HAS_MSG_OOB symbol,
	which indicates that the MSG_OOB is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_msg_peek (d_socket.U):
	This variable conditionally defines the HAS_MSG_PEEK symbol,
	which indicates that the MSG_PEEK is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_msg_proxy (d_socket.U):
	This variable conditionally defines the HAS_MSG_PROXY symbol,
	which indicates that the MSG_PROXY is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_msgctl (d_msgctl.U):
	This variable conditionally defines the HAS_MSGCTL symbol, which
	indicates to the C program that the msgctl() routine is available.

d_msgget (d_msgget.U):
	This variable conditionally defines the HAS_MSGGET symbol, which
	indicates to the C program that the msgget() routine is available.

d_msghdr_s (d_msghdr_s.U):
	This variable conditionally defines the HAS_STRUCT_MSGHDR symbol,
	which indicates that the struct msghdr is supported.

d_msgrcv (d_msgrcv.U):
	This variable conditionally defines the HAS_MSGRCV symbol, which
	indicates to the C program that the msgrcv() routine is available.

d_msgsnd (d_msgsnd.U):
	This variable conditionally defines the HAS_MSGSND symbol, which
	indicates to the C program that the msgsnd() routine is available.

d_msync (d_msync.U):
	This variable conditionally defines HAS_MSYNC if msync() is
	available to synchronize a mapped file.

d_munmap (d_munmap.U):
	This variable conditionally defines HAS_MUNMAP if munmap() is
	available to unmap a region mapped by mmap().

d_mymalloc (mallocsrc.U):
	This variable conditionally defines MYMALLOC in case other parts
	of the source want to take special action if MYMALLOC is used.
	This may include different sorts of profiling or error detection.

d_nan (d_nan.U):
	This variable conditionally defines HAS_NAN if nan() is
	available to generate NaN.

d_nanosleep (d_nanosleep.U):
	This variable conditionally defines HAS_NANOSLEEP
	if nanosleep() is available to sleep with 1E-9 sec accuracy.

d_ndbm (i_ndbm.U):
	This variable conditionally defines the HAS_NDBM symbol, which
	indicates that both the ndbm.h include file and an appropriate ndbm
	library exist.  Consult the different i_*ndbm variables
	to find out the actual include location.  Sometimes, a system has the
	header file but not the library.  This variable will only be set if
	the system has both.

d_ndbm_h_uses_prototypes (i_ndbm.U):
	This variable conditionally defines the NDBM_H_USES_PROTOTYPES symbol,
	which indicates that the ndbm.h include file uses real ANSI C
	prototypes instead of K&R style function declarations. K&R style
	declarations are unsupported in C++, so the include file requires
	special handling when using a C++ compiler and this variable is
	undefined. Consult the different d_*ndbm_h_uses_prototypes variables
	to get the same information for alternative ndbm.h include files.

d_nearbyint (d_nearbyint.U):
	This variable conditionally defines HAS_NEARBYINT if nearbyint()
	is available to return the integral value closest to (according to
	the current rounding mode) to x.

d_newlocale (d_newlocale.U):
	This variable conditionally defines the HAS_NEWLOCALE symbol, which
	indicates to the C program that the newlocale() routine is available
	to return a new locale object or modify an existing locale object.

d_nextafter (d_nextafter.U):
	This variable conditionally defines HAS_NEXTAFTER if nextafter()
	is available to return the next machine representable double from
	x in direction y.

d_nexttoward (d_nexttoward.U):
	This variable conditionally defines HAS_NEXTTOWARD if nexttoward()
	is available to return the next machine representable long double from
	x in direction y.

d_nice (d_nice.U):
	This variable conditionally defines the HAS_NICE symbol, which
	indicates to the C program that the nice() routine is available.

d_nl_langinfo (d_nl_langinfo.U):
	This variable conditionally defines the HAS_NL_LANGINFO symbol, which
	indicates to the C program that the nl_langinfo() routine is available.

d_nl_langinfo_l (d_nl_langinfo.U):
	This variable conditionally defines the HAS_NL_LANGINFO_L symbol, which
	indicates to the C program that the nl_langinfo_l() routine is available.

d_non_int_bitfields (d_bitfield.U):
	This variable conditionally defines HAS_NON_INT_BITFIELDS
	which indicates that the C compiler accepts struct bitfields of sizes
	that aren't 'int' or 'unsigned int'

d_nv_preserves_uv (perlxv.U):
	This variable indicates whether a variable of type nvtype
	can preserve all the bits a variable of type uvtype.

d_nv_zero_is_allbits_zero (perlxv.U):
	This variable indicates whether a variable of type nvtype
	stores 0.0 in memory as all bits zero.

d_off64_t (d_off64_t.U):
	This symbol will be defined if the C compiler supports off64_t.

d_old_pthread_create_joinable (d_pthrattrj.U):
	This variable conditionally defines pthread_create_joinable.
	undef if pthread.h defines PTHREAD_CREATE_JOINABLE.

d_oldpthreads (usethreads.U):
	This variable conditionally defines the OLD_PTHREADS_API symbol,
	and indicates that Perl should be built to use the old
	draft POSIX threads API.  This is only potentially meaningful if
	usethreads is set.

d_oldsock (d_socket.U):
	This variable conditionally defines the OLDSOCKET symbol, which
	indicates that the BSD socket interface is based on 4.1c and not 4.2.

d_open3 (d_open3.U):
	This variable conditionally defines the HAS_OPEN3 manifest constant,
	which indicates to the C program that the 3 argument version of
	the open(2) function is available.

d_openat (d_fsat.U):
	This variable conditionally defines the HAS_OPENAT symbol, which
	indicates the POSIX openat() function is available.

d_pathconf (d_pathconf.U):
	This variable conditionally defines the HAS_PATHCONF symbol, which
	indicates to the C program that the pathconf() routine is available
	to determine file-system related limits and options associated
	with a given filename.

d_pause (d_pause.U):
	This variable conditionally defines the HAS_PAUSE symbol, which
	indicates to the C program that the pause() routine is available
	to suspend a process until a signal is received.

d_perl_lc_all_category_positions_init (disparate_lc_all.U):
	This symbol, if defined, indicates that $lc_all_category_positions_init
	is valid

d_perl_lc_all_separator (disparate_lc_all.U):
	This symbol, if defined, indicates that $perl_lc_all_separator is valid

d_perl_lc_all_uses_name_value_pairs (disparate_lc_all.U):
	This symbol, if defined, indicates that the string returned by
	setlocale(LC_ALL, NULL) uses 'name=value;' pairs to indicate what each
	category's locale is when they aren't all set to the same locale.
	When not defined, the platform uses positional notation.

d_perl_otherlibdirs (otherlibdirs.U):
	This variable conditionally defines PERL_OTHERLIBDIRS, which
	contains a colon-separated set of paths for the perl binary to
	include in @INC.  See also otherlibdirs.

d_phostname (d_gethname.U):
	This variable conditionally defines the HAS_PHOSTNAME symbol, which
	contains the shell command which, when fed to popen(), may be
	used to derive the host name.

d_pipe (d_pipe.U):
	This variable conditionally defines the HAS_PIPE symbol, which
	indicates to the C program that the pipe() routine is available
	to create an inter-process channel.

d_pipe2 (d_pipe2.U):
	This variable conditionally defines the HAS_PIPE2 symbol, which
	indicates to the C program that the pipe2() routine is available
	to create an inter-process channel.

d_poll (d_poll.U):
	This variable conditionally defines the HAS_POLL symbol, which
	indicates to the C program that the poll() routine is available
	to poll active file descriptors.

d_portable (d_portable.U):
	This variable conditionally defines the PORTABLE symbol, which
	indicates to the C program that it should not assume that it is
	running on the machine it was compiled on.

d_prctl (d_prctl.U):
	This variable conditionally defines the HAS_PRCTL symbol, which
	indicates to the C program that the prctl() routine is available.
	Note that there are at least two prctl variants: Linux and Irix.
	While they are somewhat similar, they are incompatible.

d_prctl_set_name (d_prctl.U):
	This variable conditionally defines the HAS_PRCTL_SET_NAME symbol,
	which indicates to the C program that the prctl() routine supports
	the PR_SET_NAME option.

d_PRId64 (quadfio.U):
	This variable conditionally defines the PERL_PRId64 symbol, which
	indicates that stdio has a symbol to print 64-bit decimal numbers.

d_PRIeldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.

d_PRIEUldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.
	The 'U' in the name is to separate this from d_PRIeldbl so that even
	case-blind systems can see the difference.

d_PRIfldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.

d_PRIFUldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.
	The 'U' in the name is to separate this from d_PRIfldbl so that even
	case-blind systems can see the difference.

d_PRIgldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.

d_PRIGUldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to print long doubles.
	The 'U' in the name is to separate this from d_PRIgldbl so that even
	case-blind systems can see the difference.

d_PRIi64 (quadfio.U):
	This variable conditionally defines the PERL_PRIi64 symbol, which
	indicates that stdio has a symbol to print 64-bit decimal numbers.

d_printf_format_null (d_attribut.U):
	This variable conditionally defines PRINTF_FORMAT_NULL_OK, which
	indicates the C compiler allows printf-like formats to be null.

d_PRIo64 (quadfio.U):
	This variable conditionally defines the PERL_PRIo64 symbol, which
	indicates that stdio has a symbol to print 64-bit octal numbers.

d_PRIu64 (quadfio.U):
	This variable conditionally defines the PERL_PRIu64 symbol, which
	indicates that stdio has a symbol to print 64-bit unsigned decimal
	numbers.

d_PRIx64 (quadfio.U):
	This variable conditionally defines the PERL_PRIx64 symbol, which
	indicates that stdio has a symbol to print 64-bit hexadecimal numbers.

d_PRIXU64 (quadfio.U):
	This variable conditionally defines the PERL_PRIXU64 symbol, which
	indicates that stdio has a symbol to print 64-bit hExADECimAl numbers.
	The 'U' in the name is to separate this from d_PRIx64 so that even
	case-blind systems can see the difference.

d_procselfexe (d_procselfexe.U):
	Defined if $procselfexe is symlink to the absolute
	pathname of the executing program.

d_pseudofork (d_vfork.U):
	This variable conditionally defines the HAS_PSEUDOFORK symbol,
	which indicates that an emulation of the fork routine is available.

d_pthread_atfork (d_pthread_atfork.U):
	This variable conditionally defines the HAS_PTHREAD_ATFORK symbol,
	which indicates to the C program that the pthread_atfork()
	routine is available.

d_pthread_attr_setscope (d_pthread_attr_ss.U):
	This variable conditionally defines HAS_PTHREAD_ATTR_SETSCOPE if
	pthread_attr_setscope() is available to set the contention scope
	attribute of a thread attribute object.

d_pthread_yield (d_pthread_y.U):
	This variable conditionally defines the HAS_PTHREAD_YIELD
	symbol if the pthread_yield routine is available to yield
	the execution of the current thread.

d_ptrdiff_t (d_ptrdiff_t.U):
	This symbol will be defined if the C compiler supports ptrdiff_t.

d_pwage (i_pwd.U):
	This variable conditionally defines PWAGE, which indicates
	that struct passwd contains pw_age.

d_pwchange (i_pwd.U):
	This variable conditionally defines PWCHANGE, which indicates
	that struct passwd contains pw_change.

d_pwclass (i_pwd.U):
	This variable conditionally defines PWCLASS, which indicates
	that struct passwd contains pw_class.

d_pwcomment (i_pwd.U):
	This variable conditionally defines PWCOMMENT, which indicates
	that struct passwd contains pw_comment.

d_pwexpire (i_pwd.U):
	This variable conditionally defines PWEXPIRE, which indicates
	that struct passwd contains pw_expire.

d_pwgecos (i_pwd.U):
	This variable conditionally defines PWGECOS, which indicates
	that struct passwd contains pw_gecos.

d_pwpasswd (i_pwd.U):
	This variable conditionally defines PWPASSWD, which indicates
	that struct passwd contains pw_passwd.

d_pwquota (i_pwd.U):
	This variable conditionally defines PWQUOTA, which indicates
	that struct passwd contains pw_quota.

d_qgcvt (d_qgcvt.U):
	This variable conditionally defines the HAS_QGCVT symbol, which
	indicates to the C program that the qgcvt() routine is available.

d_quad (quadtype.U):
	This variable, if defined, tells that there's a 64-bit integer type,
	quadtype.

d_querylocale (d_newlocale.U):
	This variable conditionally defines the HAS_QUERYLOCALE symbol, which
	indicates to the C program that the querylocale() routine is available
	to return the name of the locale for a category mask.

d_random_r (d_random_r.U):
	This variable conditionally defines the HAS_RANDOM_R symbol,
	which indicates to the C program that the random_r()
	routine is available.

d_re_comp (d_regcmp.U):
	This variable conditionally defines the HAS_RECOMP symbol, which
	indicates to the C program that the re_comp() routine is available
	for regular pattern matching (usually on BSD). If so, it is likely that
	re_exec() exists.

d_readdir (d_readdir.U):
	This variable conditionally defines HAS_READDIR if readdir() is
	available to read directory entries.

d_readdir64_r (d_readdir64_r.U):
	This variable conditionally defines the HAS_READDIR64_R symbol,
	which indicates to the C program that the readdir64_r()
	routine is available.

d_readdir_r (d_readdir_r.U):
	This variable conditionally defines the HAS_READDIR_R symbol,
	which indicates to the C program that the readdir_r()
	routine is available.

d_readlink (d_readlink.U):
	This variable conditionally defines the HAS_READLINK symbol, which
	indicates to the C program that the readlink() routine is available
	to read the value of a symbolic link.

d_readv (d_readv.U):
	This variable conditionally defines the HAS_READV symbol, which
	indicates to the C program that the readv() routine is available.

d_recvmsg (d_recvmsg.U):
	This variable conditionally defines the HAS_RECVMSG symbol, which
	indicates to the C program that the recvmsg() routine is available.

d_regcmp (d_regcmp.U):
	This variable conditionally defines the HAS_REGCMP symbol, which
	indicates to the C program that the regcmp() routine is available
	for regular pattern matching (usually on System V).

d_regcomp (d_regcmp.U):
	This variable conditionally defines the HAS_REGCOMP symbol, which
	indicates to the C program that the regcomp() routine is available
	for regular pattern matching (usually on POSIX.2 conforming systems).

d_remainder (d_remainder.U):
	This variable conditionally defines the HAS_REMAINDER symbol, which
	indicates to the C program that the remainder() routine is available.

d_remquo (d_remquo.U):
	This variable conditionally defines the HAS_REMQUO symbol, which
	indicates to the C program that the remquo() routine is available.

d_rename (d_rename.U):
	This variable conditionally defines the HAS_RENAME symbol, which
	indicates to the C program that the rename() routine is available
	to rename files.

d_renameat (d_fsat.U):
	This variable conditionally defines the HAS_RENAMEAT symbol, which
	indicates the POSIX renameat() function is available.

d_rewinddir (d_readdir.U):
	This variable conditionally defines HAS_REWINDDIR if rewinddir() is
	available.

d_rint (d_rint.U):
	This variable conditionally defines the HAS_RINT symbol, which
	indicates to the C program that the rint() routine is available.

d_rmdir (d_rmdir.U):
	This variable conditionally defines HAS_RMDIR if rmdir() is
	available to remove directories.

d_round (d_round.U):
	This variable conditionally defines the HAS_ROUND symbol, which
	indicates to the C program that the round() routine is available.

d_sbrkproto (d_sbrkproto.U):
	This variable conditionally defines the HAS_SBRK_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the sbrk() function.  Otherwise, it is
	up to the program to supply one.

d_scalbn (d_scalbn.U):
	This variable conditionally defines the HAS_SCALBN symbol, which
	indicates to the C program that the scalbn() routine is available.

d_scalbnl (d_scalbnl.U):
	This variable conditionally defines the HAS_SCALBNL symbol, which
	indicates to the C program that the scalbnl() routine is available.
	If ilogbl is also present we can emulate frexpl.

d_sched_yield (d_pthread_y.U):
	This variable conditionally defines the HAS_SCHED_YIELD
	symbol if the sched_yield routine is available to yield
	the execution of the current thread.

d_scm_rights (d_socket.U):
	This variable conditionally defines the HAS_SCM_RIGHTS symbol,
	which indicates that the SCM_RIGHTS is available.  #ifdef is
	not enough because it may be an enum, glibc has been known to do this.

d_SCNfldbl (longdblfio.U):
	This variable conditionally defines the PERL_PRIfldbl symbol, which
	indicates that stdio has a symbol to scan long doubles.

d_seekdir (d_readdir.U):
	This variable conditionally defines HAS_SEEKDIR if seekdir() is
	available.

d_select (d_select.U):
	This variable conditionally defines HAS_SELECT if select() is
	available to select active file descriptors. A <sys/time.h>
	inclusion may be necessary for the timeout field.

d_sem (d_sem.U):
	This variable conditionally defines the HAS_SEM symbol, which
	indicates that the entire sem*(2) library is present.

d_semctl (d_semctl.U):
	This variable conditionally defines the HAS_SEMCTL symbol, which
	indicates to the C program that the semctl() routine is available.

d_semctl_semid_ds (d_union_semun.U):
	This variable conditionally defines USE_SEMCTL_SEMID_DS, which
	indicates that struct semid_ds * is to be used for semctl IPC_STAT.

d_semctl_semun (d_union_semun.U):
	This variable conditionally defines USE_SEMCTL_SEMUN, which
	indicates that union semun is to be used for semctl IPC_STAT.

d_semget (d_semget.U):
	This variable conditionally defines the HAS_SEMGET symbol, which
	indicates to the C program that the semget() routine is available.

d_semop (d_semop.U):
	This variable conditionally defines the HAS_SEMOP symbol, which
	indicates to the C program that the semop() routine is available.

d_sendmsg (d_sendmsg.U):
	This variable conditionally defines the HAS_SENDMSG symbol, which
	indicates to the C program that the sendmsg() routine is available.

d_setegid (d_setegid.U):
	This variable conditionally defines the HAS_SETEGID symbol, which
	indicates to the C program that the setegid() routine is available
	to change the effective gid of the current program.

d_setenv (d_setenv.U):
	This variable conditionally defines the HAS_SETENV symbol, which
	indicates to the C program that the setenv routine is available.

d_seteuid (d_seteuid.U):
	This variable conditionally defines the HAS_SETEUID symbol, which
	indicates to the C program that the seteuid() routine is available
	to change the effective uid of the current program.

d_setgrent (d_setgrent.U):
	This variable conditionally defines the HAS_SETGRENT symbol, which
	indicates to the C program that the setgrent() routine is available
	for initializing sequential access to the group database.

d_setgrent_r (d_setgrent_r.U):
	This variable conditionally defines the HAS_SETGRENT_R symbol,
	which indicates to the C program that the setgrent_r()
	routine is available.

d_setgrps (d_setgrps.U):
	This variable conditionally defines the HAS_SETGROUPS symbol, which
	indicates to the C program that the setgroups() routine is available
	to set the list of process groups.

d_sethent (d_sethent.U):
	This variable conditionally defines HAS_SETHOSTENT if sethostent() is
	available.

d_sethostent_r (d_sethostent_r.U):
	This variable conditionally defines the HAS_SETHOSTENT_R symbol,
	which indicates to the C program that the sethostent_r()
	routine is available.

d_setitimer (d_setitimer.U):
	This variable conditionally defines the HAS_SETITIMER symbol, which
	indicates to the C program that the setitimer() routine is available.

d_setlinebuf (d_setlnbuf.U):
	This variable conditionally defines the HAS_SETLINEBUF symbol, which
	indicates to the C program that the setlinebuf() routine is available
	to change stderr or stdout from block-buffered or unbuffered to a
	line-buffered mode.

d_setlocale (d_setlocale.U):
	This variable conditionally defines HAS_SETLOCALE if setlocale() is
	available to handle locale-specific ctype implementations.

d_setlocale_accepts_any_locale_name (d_setlocale.U):
	This variable conditionally defines SETLOCALE_ACCEPTS_ANY_LOCALE_NAME
	if setlocale() accepts any locale name.

d_setlocale_r (d_setlocale_r.U):
	This variable conditionally defines the HAS_SETLOCALE_R symbol,
	which indicates to the C program that the setlocale_r()
	routine is available.

d_setnent (d_setnent.U):
	This variable conditionally defines HAS_SETNETENT if setnetent() is
	available.

d_setnetent_r (d_setnetent_r.U):
	This variable conditionally defines the HAS_SETNETENT_R symbol,
	which indicates to the C program that the setnetent_r()
	routine is available.

d_setpent (d_setpent.U):
	This variable conditionally defines HAS_SETPROTOENT if setprotoent() is
	available.

d_setpgid (d_setpgid.U):
	This variable conditionally defines the HAS_SETPGID symbol if the
	setpgid(pid, gpid) function is available to set process group ID.

d_setpgrp (d_setpgrp.U):
	This variable conditionally defines HAS_SETPGRP if setpgrp() is
	available to set the current process group.

d_setpgrp2 (d_setpgrp2.U):
	This variable conditionally defines the HAS_SETPGRP2 symbol, which
	indicates to the C program that the setpgrp2() (as in DG/UX) routine
	is available to set the current process group.

d_setprior (d_setprior.U):
	This variable conditionally defines HAS_SETPRIORITY if setpriority()
	is available to set a process's priority.

d_setproctitle (d_setproctitle.U):
	This variable conditionally defines the HAS_SETPROCTITLE symbol,
	which indicates to the C program that the setproctitle() routine
	is available.

d_setprotoent_r (d_setprotoent_r.U):
	This variable conditionally defines the HAS_SETPROTOENT_R symbol,
	which indicates to the C program that the setprotoent_r()
	routine is available.

d_setpwent (d_setpwent.U):
	This variable conditionally defines the HAS_SETPWENT symbol, which
	indicates to the C program that the setpwent() routine is available
	for initializing sequential access to the passwd database.

d_setpwent_r (d_setpwent_r.U):
	This variable conditionally defines the HAS_SETPWENT_R symbol,
	which indicates to the C program that the setpwent_r()
	routine is available.

d_setregid (d_setregid.U):
	This variable conditionally defines HAS_SETREGID if setregid() is
	available to change the real and effective gid of the current
	process.

d_setresgid (d_setregid.U):
	This variable conditionally defines HAS_SETRESGID if setresgid() is
	available to change the real, effective and saved gid of the current
	process.

d_setresuid (d_setreuid.U):
	This variable conditionally defines HAS_SETREUID if setresuid() is
	available to change the real, effective and saved uid of the current
	process.

d_setreuid (d_setreuid.U):
	This variable conditionally defines HAS_SETREUID if setreuid() is
	available to change the real and effective uid of the current
	process.

d_setrgid (d_setrgid.U):
	This variable conditionally defines the HAS_SETRGID symbol, which
	indicates to the C program that the setrgid() routine is available
	to change the real gid of the current program.

d_setruid (d_setruid.U):
	This variable conditionally defines the HAS_SETRUID symbol, which
	indicates to the C program that the setruid() routine is available
	to change the real uid of the current program.

d_setsent (d_setsent.U):
	This variable conditionally defines HAS_SETSERVENT if setservent() is
	available.

d_setservent_r (d_setservent_r.U):
	This variable conditionally defines the HAS_SETSERVENT_R symbol,
	which indicates to the C program that the setservent_r()
	routine is available.

d_setsid (d_setsid.U):
	This variable conditionally defines HAS_SETSID if setsid() is
	available to set the process group ID.

d_setvbuf (d_setvbuf.U):
	This variable conditionally defines the HAS_SETVBUF symbol, which
	indicates to the C program that the setvbuf() routine is available
	to change buffering on an open stdio stream.

d_shm (d_shm.U):
	This variable conditionally defines the HAS_SHM symbol, which
	indicates that the entire shm*(2) library is present.

d_shmat (d_shmat.U):
	This variable conditionally defines the HAS_SHMAT symbol, which
	indicates to the C program that the shmat() routine is available.

d_shmatprototype (d_shmat.U):
	This variable conditionally defines the HAS_SHMAT_PROTOTYPE
	symbol, which indicates that sys/shm.h has a prototype for
	shmat.

d_shmctl (d_shmctl.U):
	This variable conditionally defines the HAS_SHMCTL symbol, which
	indicates to the C program that the shmctl() routine is available.

d_shmdt (d_shmdt.U):
	This variable conditionally defines the HAS_SHMDT symbol, which
	indicates to the C program that the shmdt() routine is available.

d_shmget (d_shmget.U):
	This variable conditionally defines the HAS_SHMGET symbol, which
	indicates to the C program that the shmget() routine is available.

d_sigaction (d_sigaction.U):
	This variable conditionally defines the HAS_SIGACTION symbol, which
	indicates that the Vr4 sigaction() routine is available.

d_siginfo_si_addr (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_ADDR symbol,
	which indicates that the siginfo_t struct has the si_addr member.

d_siginfo_si_band (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_BAND symbol,
	which indicates that the siginfo_t struct has the si_band member.

d_siginfo_si_errno (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_ERRNO symbol,
	which indicates that the siginfo_t struct has the si_errno member.

d_siginfo_si_fd (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_FD symbol,
	which indicates that the siginfo_t struct has the si_fd member.

d_siginfo_si_pid (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_PID symbol,
	which indicates that the siginfo_t struct has the si_pid member.

d_siginfo_si_status (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_STATUS symbol,
	which indicates that the siginfo_t struct has the si_status member.

d_siginfo_si_uid (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_UID symbol,
	which indicates that the siginfo_t struct has the si_uid member.

d_siginfo_si_value (d_siginfo_si.U):
	This variable conditionally defines the HAS_SIGINFO_SI_VALUE symbol,
	which indicates that the siginfo_t struct has the si_value member.

d_signbit (d_signbit.U):
	This variable conditionally defines the HAS_SIGNBIT symbol, which
	indicates to the C program that the signbit() routine is available
	and safe to use with perl's intern NV type.

d_sigprocmask (d_sigprocmask.U):
	This variable conditionally defines HAS_SIGPROCMASK
	if sigprocmask() is available to examine or change the signal mask
	of the calling process.

d_sigsetjmp (d_sigsetjmp.U):
	This variable conditionally defines the HAS_SIGSETJMP symbol,
	which indicates that the sigsetjmp() routine is available to
	call setjmp() and optionally save the process's signal mask.

d_sin6_scope_id (d_socket.U):
	This variable conditionally defines the HAS_SIN6_SCOPE_ID symbol, which
	indicates that a struct sockaddr_in6 structure has the sin6_scope_id
	member.

d_sitearch (sitearch.U):
	This variable conditionally defines SITEARCH to hold the pathname
	of architecture-dependent library files for $package.  If
	$sitearch is the same as $archlib, then this is set to undef.

d_snprintf (d_snprintf.U):
	This variable conditionally defines the HAS_SNPRINTF symbol, which
	indicates to the C program that the snprintf () library function
	is available.

d_sockaddr_in6 (d_socket.U):
	This variable conditionally defines the HAS_SOCKADDR_IN6 symbol, which
	indicates the availability of a struct sockaddr_in6.

d_sockaddr_sa_len (d_socket.U):
	This variable conditionally defines the HAS_SOCKADDR_SA_LEN symbol,
	which indicates that a struct sockaddr structure has the sa_len
	member.

d_sockaddr_storage (d_socket.U):
	This variable conditionally defines the HAS_SOCKADDR_STORAGE symbol,
	which indicates the availability of a struct sockaddr_storage.

d_sockatmark (d_sockatmark.U):
	This variable conditionally defines the HAS_SOCKATMARK symbol, which
	indicates to the C program that the sockatmark() routine is available.

d_sockatmarkproto (d_sockatmarkproto.U):
	This variable conditionally defines the HAS_SOCKATMARK_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the sockatmark() function.  Otherwise, it is
	up to the program to supply one.

d_socket (d_socket.U):
	This variable conditionally defines HAS_SOCKET, which indicates
	that the BSD socket interface is supported.

d_socklen_t (d_socklen_t.U):
	This symbol will be defined if the C compiler supports socklen_t.

d_sockpair (d_socket.U):
	This variable conditionally defines the HAS_SOCKETPAIR symbol, which
	indicates that the BSD socketpair() is supported.

d_socks5_init (d_socks5_init.U):
	This variable conditionally defines the HAS_SOCKS5_INIT symbol, which
	indicates to the C program that the socks5_init() routine is available.

d_sqrtl (d_sqrtl.U):
	This variable conditionally defines the HAS_SQRTL symbol, which
	indicates to the C program that the sqrtl() routine is available.

d_srand48_r (d_srand48_r.U):
	This variable conditionally defines the HAS_SRAND48_R symbol,
	which indicates to the C program that the srand48_r()
	routine is available.

d_srandom_r (d_srandom_r.U):
	This variable conditionally defines the HAS_SRANDOM_R symbol,
	which indicates to the C program that the srandom_r()
	routine is available.

d_sresgproto (d_sresgproto.U):
	This variable conditionally defines the HAS_SETRESGID_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the setresgid() function.  Otherwise, it is
	up to the program to supply one.

d_sresuproto (d_sresuproto.U):
	This variable conditionally defines the HAS_SETRESUID_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the setresuid() function.  Otherwise, it is
	up to the program to supply one.

d_stat (d_stat.U):
	This variable conditionally defines HAS_STAT if stat() is
	available to get file status.

d_statblks (d_statblks.U):
	This variable conditionally defines USE_STAT_BLOCKS
	if this system has a stat structure declaring
	st_blksize and st_blocks.

d_statfs_f_flags (d_statfs_f_flags.U):
	This variable conditionally defines the HAS_STRUCT_STATFS_F_FLAGS
	symbol, which indicates to struct statfs from has f_flags member.
	This kind of struct statfs is coming from sys/mount.h (BSD),
	not from sys/statfs.h (SYSV).

d_statfs_s (d_statfs_s.U):
	This variable conditionally defines the HAS_STRUCT_STATFS symbol,
	which indicates that the struct statfs is supported.

d_static_inline (d_static_inline.U):
	This variable conditionally defines the HAS_STATIC_INLINE symbol,
	which indicates that the C compiler supports C99-style static
	inline.  That is, the function can't be called from another
	translation unit.

d_statvfs (d_statvfs.U):
	This variable conditionally defines the HAS_STATVFS symbol, which
	indicates to the C program that the statvfs() routine is available.

d_stdio_cnt_lval (d_stdstdio.U):
	This variable conditionally defines STDIO_CNT_LVALUE if the
	FILE_cnt macro can be used as an lvalue.

d_stdio_ptr_lval (d_stdstdio.U):
	This variable conditionally defines STDIO_PTR_LVALUE if the
	FILE_ptr macro can be used as an lvalue.

d_stdio_ptr_lval_nochange_cnt (d_stdstdio.U):
	This symbol is defined if using the FILE_ptr macro as an lvalue
	to increase the pointer by n leaves File_cnt(fp) unchanged.

d_stdio_ptr_lval_sets_cnt (d_stdstdio.U):
	This symbol is defined if using the FILE_ptr macro as an lvalue
	to increase the pointer by n has the side effect of decreasing the
	value of File_cnt(fp) by n.

d_stdio_stream_array (stdio_streams.U):
	This variable tells whether there is an array holding
	the stdio streams.

d_stdiobase (d_stdstdio.U):
	This variable conditionally defines USE_STDIO_BASE if this system
	has a FILE structure declaring a usable _base field (or equivalent)
	in stdio.h.

d_stdstdio (d_stdstdio.U):
	This variable conditionally defines USE_STDIO_PTR if this system
	has a FILE structure declaring usable _ptr and _cnt fields (or
	equivalent) in stdio.h.

d_strcoll (d_strcoll.U):
	This variable conditionally defines HAS_STRCOLL if strcoll() is
	available to compare strings using collating information.

d_strerror_l (d_strerror_l.U):
	This variable conditionally defines the HAS_STRERROR_L symbol, which
	indicates to the C program that the strerror_l() routine is available
	to return the error message for a given errno value in a particular
	locale (identified by a locale_t object).

d_strerror_r (d_strerror_r.U):
	This variable conditionally defines the HAS_STRERROR_R symbol,
	which indicates to the C program that the strerror_r()
	routine is available.

d_strftime (d_strftime.U):
	This variable conditionally defines the HAS_STRFTIME symbol, which
	indicates to the C program that the strftime() routine is available.

d_strlcat (d_strlcat.U):
	This variable conditionally defines the HAS_STRLCAT symbol, which
	indicates to the C program that the strlcat () routine is available.

d_strlcpy (d_strlcpy.U):
	This variable conditionally defines the HAS_STRLCPY symbol, which
	indicates to the C program that the strlcpy () routine is available.

d_strnlen (d_strnlen.U):
	This variable conditionally defines the HAS_STRNLEN symbol, which
	indicates to the C program that the strnlen () routine is available.

d_strtod (d_strtod.U):
	This variable conditionally defines the HAS_STRTOD symbol, which
	indicates to the C program that the strtod() routine is available
	to provide better numeric string conversion than atof().

d_strtod_l (d_strtod_l.U):
	This variable conditionally defines the HAS_STRTOD_L symbol, which
	indicates to the C program that the strtod_l() routine is available.

d_strtol (d_strtol.U):
	This variable conditionally defines the HAS_STRTOL symbol, which
	indicates to the C program that the strtol() routine is available
	to provide better numeric string conversion than atoi() and friends.

d_strtold (d_strtold.U):
	This variable conditionally defines the HAS_STRTOLD symbol, which
	indicates to the C program that the strtold() routine is available.

d_strtold_l (d_strtold_l.U):
	This variable conditionally defines the HAS_STRTOLD_L symbol, which
	indicates to the C program that the strtold_l() routine is available.

d_strtoll (d_strtoll.U):
	This variable conditionally defines the HAS_STRTOLL symbol, which
	indicates to the C program that the strtoll() routine is available.

d_strtoq (d_strtoq.U):
	This variable conditionally defines the HAS_STRTOQ symbol, which
	indicates to the C program that the strtoq() routine is available.

d_strtoul (d_strtoul.U):
	This variable conditionally defines the HAS_STRTOUL symbol, which
	indicates to the C program that the strtoul() routine is available
	to provide conversion of strings to unsigned long.

d_strtoull (d_strtoull.U):
	This variable conditionally defines the HAS_STRTOULL symbol, which
	indicates to the C program that the strtoull() routine is available.

d_strtouq (d_strtouq.U):
	This variable conditionally defines the HAS_STRTOUQ symbol, which
	indicates to the C program that the strtouq() routine is available.

d_strxfrm (d_strxfrm.U):
	This variable conditionally defines HAS_STRXFRM if strxfrm() is
	available to transform strings.

d_strxfrm_l (d_strxfrm_l.U):
	This variable conditionally defines HAS_STRXFRM_L if strxfrm_l() is
	available to transform strings.

d_suidsafe (d_dosuid.U):
	This variable conditionally defines SETUID_SCRIPTS_ARE_SECURE_NOW
	if setuid scripts can be secure.  This test looks in /dev/fd/.

d_symlink (d_symlink.U):
	This variable conditionally defines the HAS_SYMLINK symbol, which
	indicates to the C program that the symlink() routine is available
	to create symbolic links.

d_syscall (d_syscall.U):
	This variable conditionally defines HAS_SYSCALL if syscall() is
	available call arbitrary system calls.

d_syscallproto (d_syscallproto.U):
	This variable conditionally defines the HAS_SYSCALL_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the syscall() function.  Otherwise, it is
	up to the program to supply one.

d_sysconf (d_sysconf.U):
	This variable conditionally defines the HAS_SYSCONF symbol, which
	indicates to the C program that the sysconf() routine is available
	to determine system related limits and options.

d_sysernlst (d_strerror.U):
	This variable conditionally defines HAS_SYS_ERRNOLIST if sys_errnolist[]
	is available to translate error numbers to the symbolic name.

d_syserrlst (d_strerror.U):
	This variable conditionally defines HAS_SYS_ERRLIST if sys_errlist[] is
	available to translate error numbers to strings.

d_system (d_system.U):
	This variable conditionally defines HAS_SYSTEM if system() is
	available to issue a shell command.

d_tcgetpgrp (d_tcgtpgrp.U):
	This variable conditionally defines the HAS_TCGETPGRP symbol, which
	indicates to the C program that the tcgetpgrp() routine is available.
	to get foreground process group ID.

d_tcsetpgrp (d_tcstpgrp.U):
	This variable conditionally defines the HAS_TCSETPGRP symbol, which
	indicates to the C program that the tcsetpgrp() routine is available
	to set foreground process group ID.

d_telldir (d_readdir.U):
	This variable conditionally defines HAS_TELLDIR if telldir() is
	available.

d_telldirproto (d_telldirproto.U):
	This variable conditionally defines the HAS_TELLDIR_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the telldir() function.  Otherwise, it is
	up to the program to supply one.

d_tgamma (d_tgamma.U):
	This variable conditionally defines the HAS_TGAMMA symbol, which
	indicates to the C program that the tgamma() routine is available
	for the gamma function.  See also d_lgamma.

d_thread_local (d_thread_local.U):
	This variable conditionally defines the PERL_THREAD_LOCAL symbol. In
	turn that gives a linkage specification for thread-local storage.

d_time (d_time.U):
	This variable conditionally defines the HAS_TIME symbol, which indicates
	that the time() routine exists.  The time() routine is normally
	provided on UNIX systems.

d_timegm (d_timegm.U):
	This variable conditionally defines the HAS_TIMEGM symbol, which
	indicates to the C program that the timegm () routine is available.

d_times (d_times.U):
	This variable conditionally defines the HAS_TIMES symbol, which indicates
	that the times() routine exists.  The times() routine is normally
	provided on UNIX systems. You may have to include <sys/times.h>.

d_tm_tm_gmtoff (i_time.U):
	This variable conditionally defines HAS_TM_TM_GMTOFF, which indicates
	to the C program that the struct tm has the tm_gmtoff field.

d_tm_tm_zone (i_time.U):
	This variable conditionally defines HAS_TM_TM_ZONE, which indicates
	to the C program that the struct tm has the tm_zone field.

d_tmpnam_r (d_tmpnam_r.U):
	This variable conditionally defines the HAS_TMPNAM_R symbol,
	which indicates to the C program that the tmpnam_r()
	routine is available.

d_towlower (d_towlower.U):
	This variable conditionally defines the HAS_TOWLOWER symbol, which
	indicates to the C program that the towlower() routine is available.

d_towupper (d_towupper.U):
	This variable conditionally defines the HAS_TOWUPPER symbol, which
	indicates to the C program that the towupper() routine is available.

d_trunc (d_trunc.U):
	This variable conditionally defines the HAS_TRUNC symbol, which
	indicates to the C program that the trunc() routine is available
	to round doubles towards zero.

d_truncate (d_truncate.U):
	This variable conditionally defines HAS_TRUNCATE if truncate() is
	available to truncate files.

d_truncl (d_truncl.U):
	This variable conditionally defines the HAS_TRUNCL symbol, which
	indicates to the C program that the truncl() routine is available
	to round long doubles towards zero. If copysignl is also present,
	we can emulate modfl.

d_ttyname_r (d_ttyname_r.U):
	This variable conditionally defines the HAS_TTYNAME_R symbol,
	which indicates to the C program that the ttyname_r()
	routine is available.

d_tzname (d_tzname.U):
	This variable conditionally defines HAS_TZNAME if tzname[] is
	available to access timezone names.

d_u32align (d_u32align.U):
	This variable tells whether you must access character data
	through U32-aligned pointers.

d_ualarm (d_ualarm.U):
	This variable conditionally defines the HAS_UALARM symbol, which
	indicates to the C program that the ualarm() routine is available.

d_umask (d_umask.U):
	This variable conditionally defines the HAS_UMASK symbol, which
	indicates to the C program that the umask() routine is available.
	to set and get the value of the file creation mask.

d_uname (d_gethname.U):
	This variable conditionally defines the HAS_UNAME symbol, which
	indicates to the C program that the uname() routine may be
	used to derive the host name.

d_union_semun (d_union_semun.U):
	This variable conditionally defines HAS_UNION_SEMUN if the
	union semun is defined by including <sys/sem.h>.

d_unlinkat (d_fsat.U):
	This variable conditionally defines the HAS_UNLINKAT symbol, which
	indicates the POSIX unlinkat() function isavailable.

d_unordered (d_unordered.U):
	This variable conditionally defines the HAS_UNORDERED symbol, which
	indicates to the C program that the unordered() routine is available.

d_unsetenv (d_unsetenv.U):
	This variable conditionally defines the HAS_UNSETENV symbol, which
	indicates to the C program that the unsetenv () routine is available.

d_uselocale (d_newlocale.U):
	This variable conditionally defines the HAS_USELOCALE symbol, which
	indicates to the C program that the uselocale() routine is available
	to set the current locale for the calling thread.

d_usleep (d_usleep.U):
	This variable conditionally defines HAS_USLEEP if usleep() is
	available to do high granularity sleeps.

d_usleepproto (d_usleepproto.U):
	This variable conditionally defines the HAS_USLEEP_PROTO symbol,
	which indicates to the C program that the system provides
	a prototype for the usleep() function.  Otherwise, it is
	up to the program to supply one.

d_ustat (d_ustat.U):
	This variable conditionally defines HAS_USTAT if ustat() is
	available to query file system statistics by dev_t.

d_vendorarch (vendorarch.U):
	This variable conditionally defined PERL_VENDORARCH.

d_vendorbin (vendorbin.U):
	This variable conditionally defines PERL_VENDORBIN.

d_vendorlib (vendorlib.U):
	This variable conditionally defines PERL_VENDORLIB.

d_vendorscript (vendorscript.U):
	This variable conditionally defines PERL_VENDORSCRIPT.

d_vfork (d_vfork.U):
	This variable conditionally defines the HAS_VFORK symbol, which
	indicates the vfork() routine is available.

d_void_closedir (d_closedir.U):
	This variable conditionally defines VOID_CLOSEDIR if closedir()
	does not return a value.

d_voidsig (d_voidsig.U):
	This variable conditionally defines VOIDSIG if this system
	declares "void (*signal(...))()" in signal.h.  The old way was to
	declare it as "int (*signal(...))()".

d_voidtty (i_sysioctl.U):
	This variable conditionally defines USE_IOCNOTTY to indicate that the
	ioctl() call with TIOCNOTTY should be used to void tty association.
	Otherwise (on USG probably), it is enough to close the standard file
	descriptors and do a setpgrp().

d_vsnprintf (d_snprintf.U):
	This variable conditionally defines the HAS_VSNPRINTF symbol, which
	indicates to the C program that the vsnprintf () library function
	is available.

d_wait4 (d_wait4.U):
	This variable conditionally defines the HAS_WAIT4 symbol, which
	indicates the wait4() routine is available.

d_waitpid (d_waitpid.U):
	This variable conditionally defines HAS_WAITPID if waitpid() is
	available to wait for child process.

d_wcrtomb (d_wcrtomb.U):
	This variable conditionally defines the HAS_WCRTOMB symbol if the
	wcrtomb() routine is available to be used to convert a wide character
	into a multi-byte character.

d_wcscmp (d_wcscmp.U):
	This variable conditionally defines the HAS_WCSCMP symbol if the
	wcscmp() routine is available and can be used to compare wide
	character strings.

d_wcstombs (d_wcstombs.U):
	This variable conditionally defines the HAS_WCSTOMBS symbol, which
	indicates to the C program that the wcstombs() routine is available
	to convert wide character strings to multibyte strings.

d_wcsxfrm (d_wcsxfrm.U):
	This variable conditionally defines the HAS_WCSXFRM symbol if the
	wcsxfrm() routine is available and can be used to compare wide
	character strings.

d_wctomb (d_wctomb.U):
	This variable conditionally defines the HAS_WCTOMB symbol, which
	indicates to the C program that the wctomb() routine is available
	to convert a wide character to a multibyte.

d_writev (d_writev.U):
	This variable conditionally defines the HAS_WRITEV symbol, which
	indicates to the C program that the writev() routine is available.

d_xenix (Guess.U):
	This variable conditionally defines the symbol XENIX, which alerts
	the C program that it runs under Xenix.

date (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the date program.  After Configure runs,
	the value is reset to a plain "date" and is not useful.

db_hashtype (i_db.U):
	This variable contains the type of the hash structure element
	in the <db.h> header file.  In older versions of DB, it was
	int, while in newer ones it is u_int32_t.

db_prefixtype (i_db.U):
	This variable contains the type of the prefix structure element
	in the <db.h> header file.  In older versions of DB, it was
	int, while in newer ones it is size_t.

db_version_major (i_db.U):
	This variable contains the major version number of
	Berkeley DB found in the <db.h> header file.

db_version_minor (i_db.U):
	This variable contains the minor version number of
	Berkeley DB found in the <db.h> header file.
	For DB version 1 this is always 0.

db_version_patch (i_db.U):
	This variable contains the patch version number of
	Berkeley DB found in the <db.h> header file.
	For DB version 1 this is always 0.

default_inc_excludes_dot (defaultincdot.U):
	When defined, remove the legacy '.' from @INC

direntrytype (i_dirent.U):
	This symbol is set to 'struct direct' or 'struct dirent' depending on
	whether dirent is available or not. You should use this pseudo type to
	portably declare your directory entries.

dlext (dlext.U):
	This variable contains the extension that is to be used for the
	dynamically loaded modules that perl generates.

dlsrc (dlsrc.U):
	This variable contains the name of the dynamic loading file that
	will be used with the package.

doubleinfbytes (infnan.U):
	This variable contains comma-separated list of hexadecimal bytes
	for the double precision infinity.

doublekind (longdblfio.U):
	This variable, if defined, encodes the type of a double:
	1 = IEEE 754 32-bit little endian,
	2 = IEEE 754 32-bit big endian,
	3 = IEEE 754 64-bit little endian,
	4 = IEEE 754 64-bit big endian,
	5 = IEEE 754 128-bit little endian,
	6 = IEEE 754 128-bit big endian,
	7 = IEEE 754 64-bit mixed endian le-be,
	8 = IEEE 754 64-bit mixed endian be-le,
	9 = VAX 32bit little endian F float format
	10 = VAX 64bit little endian D float format
	11 = VAX 64bit little endian G float format
	12 = IBM 32bit format
	13 = IBM 64bit format
	14 = Cray 64bit format
	-1 = unknown format.

doublemantbits (mantbits.U):
	This symbol, if defined, tells how many mantissa bits
	there are in double precision floating point format.
	Note that this is usually DBL_MANT_DIG minus one, since
	with the standard IEEE 754 formats DBL_MANT_DIG includes
	the implicit bit which doesn't really exist.

doublenanbytes (infnan.U):
	This variable contains comma-separated list of hexadecimal bytes
	for the double precision not-a-number.

doublesize (doublesize.U):
	This variable contains the value of the DOUBLESIZE symbol, which
	indicates to the C program how many bytes there are in a double.

drand01 (randfunc.U):
	Indicates the macro to be used to generate normalized
	random numbers.  Uses randfunc, often divided by
	(double) (((unsigned long) 1 << randbits)) in order to
	normalize the result.
	In C programs, the macro 'Drand01' is mapped to drand01.

drand48_r_proto (d_drand48_r.U):
	This variable encodes the prototype of drand48_r.
	It is zero if d_drand48_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_drand48_r
	is defined.

dtrace (usedtrace.U):
	This variable holds the location of the dtrace executable.

dtraceobject (dtraceobject.U):
	Whether we need to build an object file with the dtrace tool.

dtracexnolibs (dtraceobject.U):
	Whether dtrace accepts -xnolibs.  If available we call dtrace -h
	and dtrace -G with -xnolibs to allow dtrace to run in a jail on
	FreeBSD.

dynamic_ext (Extensions.U):
	This variable holds a list of XS extension files we want to
	link dynamically into the package.  It is used by Makefile.

eagain (nblock_io.U):
	This variable bears the symbolic errno code set by read() when no
	data is present on the file and non-blocking I/O was enabled (otherwise,
	read() blocks naturally).

ebcdic (ebcdic.U):
	This variable conditionally defines EBCDIC if this
	system uses EBCDIC encoding.

echo (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the echo program.  After Configure runs,
	the value is reset to a plain "echo" and is not useful.

egrep (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the egrep program.  After Configure runs,
	the value is reset to a plain "egrep" and is not useful.

emacs (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

endgrent_r_proto (d_endgrent_r.U):
	This variable encodes the prototype of endgrent_r.
	It is zero if d_endgrent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endgrent_r
	is defined.

endhostent_r_proto (d_endhostent_r.U):
	This variable encodes the prototype of endhostent_r.
	It is zero if d_endhostent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endhostent_r
	is defined.

endnetent_r_proto (d_endnetent_r.U):
	This variable encodes the prototype of endnetent_r.
	It is zero if d_endnetent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endnetent_r
	is defined.

endprotoent_r_proto (d_endprotoent_r.U):
	This variable encodes the prototype of endprotoent_r.
	It is zero if d_endprotoent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endprotoent_r
	is defined.

endpwent_r_proto (d_endpwent_r.U):
	This variable encodes the prototype of endpwent_r.
	It is zero if d_endpwent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endpwent_r
	is defined.

endservent_r_proto (d_endservent_r.U):
	This variable encodes the prototype of endservent_r.
	It is zero if d_endservent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_endservent_r
	is defined.

eunicefix (Init.U):
	When running under Eunice this variable contains a command which will
	convert a shell script to the proper form of text file for it to be
	executable by the shell.  On other systems it is a no-op.

exe_ext (Unix.U):
	This is an old synonym for _exe.

expr (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the expr program.  After Configure runs,
	the value is reset to a plain "expr" and is not useful.

extensions (Extensions.U):
	This variable holds a list of all extension files (both XS and
	non-xs) installed with the package.  It is propagated to Config.pm
	and is typically used to test whether a particular extension
	is available.

extern_C (Csym.U):
	ANSI C requires 'extern' where C++ requires 'extern "C"'. This
	variable can be used in Configure to do the right thing.

extras (Extras.U):
	This variable holds a list of extra modules to install.

fflushall (fflushall.U):
	This symbol, if defined, tells that to flush
	all pending stdio output one must loop through all
	the stdio file handles stored in an array and fflush them.
	Note that if fflushNULL is defined, fflushall will not
	even be probed for and will be left undefined.

fflushNULL (fflushall.U):
	This symbol, if defined, tells that fflush(NULL) correctly
	flushes all pending stdio output without side effects. In
	particular, on some platforms calling fflush(NULL) *still*
	corrupts STDIN if it is a pipe.

find (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

firstmakefile (Unix.U):
	This variable defines the first file searched by make.  On unix,
	it is makefile (then Makefile).  On case-insensitive systems,
	it might be something else.  This is only used to deal with
	convoluted make depend tricks.

flex (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

fpossize (fpossize.U):
	This variable contains the size of a fpostype in bytes.

fpostype (fpostype.U):
	This variable defines Fpos_t to be something like fpos_t, long,
	uint, or whatever type is used to declare file positions in libc.

freetype (mallocsrc.U):
	This variable contains the return type of free().  It is usually
	void, but occasionally int.

from (Cross.U):
	This variable contains the command used by Configure
	to copy files from the target host.  Useful and available
	only during Perl build.
	The string ':' if not cross-compiling.

full_ar (Loc_ar.U):
	This variable contains the full pathname to 'ar', whether or
	not the user has specified 'portability'.  This is only used
	in the Makefile.SH.

full_csh (d_csh.U):
	This variable contains the full pathname to 'csh', whether or
	not the user has specified 'portability'.  This is only used
	in the compiled C program, and we assume that all systems which
	can share this executable will have the same full pathname to
	'csh.'

full_sed (Loc_sed.U):
	This variable contains the full pathname to 'sed', whether or
	not the user has specified 'portability'.  This is only used
	in the compiled C program, and we assume that all systems which
	can share this executable will have the same full pathname to
	'sed.'

gccansipedantic (gccvers.U):
	If GNU cc (gcc) is used, this variable will enable (if set) the
	-ansi and -pedantic ccflags for building core files (through
	cflags script). (See Porting/pumpkin.pod for full description).

gccosandvers (gccvers.U):
	If GNU cc (gcc) is used, this variable holds the operating system
	and version used to compile gcc.  It is set to '' if not gcc,
	or if nothing useful can be parsed as the os version.

gccversion (gccvers.U):
	If GNU cc (gcc) is used, this variable holds '1' or '2' to
	indicate whether the compiler is version 1 or 2.  This is used in
	setting some of the default cflags.  It is set to '' if not gcc.

getgrent_r_proto (d_getgrent_r.U):
	This variable encodes the prototype of getgrent_r.
	It is zero if d_getgrent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getgrent_r
	is defined.

getgrgid_r_proto (d_getgrgid_r.U):
	This variable encodes the prototype of getgrgid_r.
	It is zero if d_getgrgid_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getgrgid_r
	is defined.

getgrnam_r_proto (d_getgrnam_r.U):
	This variable encodes the prototype of getgrnam_r.
	It is zero if d_getgrnam_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getgrnam_r
	is defined.

gethostbyaddr_r_proto (d_gethostbyaddr_r.U):
	This variable encodes the prototype of gethostbyaddr_r.
	It is zero if d_gethostbyaddr_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_gethostbyaddr_r
	is defined.

gethostbyname_r_proto (d_gethostbyname_r.U):
	This variable encodes the prototype of gethostbyname_r.
	It is zero if d_gethostbyname_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_gethostbyname_r
	is defined.

gethostent_r_proto (d_gethostent_r.U):
	This variable encodes the prototype of gethostent_r.
	It is zero if d_gethostent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_gethostent_r
	is defined.

getlogin_r_proto (d_getlogin_r.U):
	This variable encodes the prototype of getlogin_r.
	It is zero if d_getlogin_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getlogin_r
	is defined.

getnetbyaddr_r_proto (d_getnetbyaddr_r.U):
	This variable encodes the prototype of getnetbyaddr_r.
	It is zero if d_getnetbyaddr_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getnetbyaddr_r
	is defined.

getnetbyname_r_proto (d_getnetbyname_r.U):
	This variable encodes the prototype of getnetbyname_r.
	It is zero if d_getnetbyname_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getnetbyname_r
	is defined.

getnetent_r_proto (d_getnetent_r.U):
	This variable encodes the prototype of getnetent_r.
	It is zero if d_getnetent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getnetent_r
	is defined.

getprotobyname_r_proto (d_getprotobyname_r.U):
	This variable encodes the prototype of getprotobyname_r.
	It is zero if d_getprotobyname_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getprotobyname_r
	is defined.

getprotobynumber_r_proto (d_getprotobynumber_r.U):
	This variable encodes the prototype of getprotobynumber_r.
	It is zero if d_getprotobynumber_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getprotobynumber_r
	is defined.

getprotoent_r_proto (d_getprotoent_r.U):
	This variable encodes the prototype of getprotoent_r.
	It is zero if d_getprotoent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getprotoent_r
	is defined.

getpwent_r_proto (d_getpwent_r.U):
	This variable encodes the prototype of getpwent_r.
	It is zero if d_getpwent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getpwent_r
	is defined.

getpwnam_r_proto (d_getpwnam_r.U):
	This variable encodes the prototype of getpwnam_r.
	It is zero if d_getpwnam_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getpwnam_r
	is defined.

getpwuid_r_proto (d_getpwuid_r.U):
	This variable encodes the prototype of getpwuid_r.
	It is zero if d_getpwuid_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getpwuid_r
	is defined.

getservbyname_r_proto (d_getservbyname_r.U):
	This variable encodes the prototype of getservbyname_r.
	It is zero if d_getservbyname_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getservbyname_r
	is defined.

getservbyport_r_proto (d_getservbyport_r.U):
	This variable encodes the prototype of getservbyport_r.
	It is zero if d_getservbyport_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getservbyport_r
	is defined.

getservent_r_proto (d_getservent_r.U):
	This variable encodes the prototype of getservent_r.
	It is zero if d_getservent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getservent_r
	is defined.

getspnam_r_proto (d_getspnam_r.U):
	This variable encodes the prototype of getspnam_r.
	It is zero if d_getspnam_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_getspnam_r
	is defined.

gidformat (gidf.U):
	This variable contains the format string used for printing a Gid_t.

gidsign (gidsign.U):
	This variable contains the signedness of a gidtype.
	1 for unsigned, -1 for signed.

gidsize (gidsize.U):
	This variable contains the size of a gidtype in bytes.

gidtype (gidtype.U):
	This variable defines Gid_t to be something like gid_t, int,
	ushort, or whatever type is used to declare the return type
	of getgid().  Typically, it is the type of group ids in the kernel.

glibpth (libpth.U):
	This variable holds the general path (space-separated) used to
	find libraries.  It may contain directories that do not exist on
	this platform, libpth is the cleaned-up version.

gmake (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the gmake program.  After Configure runs,
	the value is reset to a plain "gmake" and is not useful.

gmtime_r_proto (d_gmtime_r.U):
	This variable encodes the prototype of gmtime_r.
	It is zero if d_gmtime_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_gmtime_r
	is defined.

gnulibc_version (d_gnulibc.U):
	This variable contains the version number of the GNU C library.
	It is usually something like '2.2.5'.  It is a plain '' if this
	is not the GNU C library, or if the version is unknown.

grep (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the grep program.  After Configure runs,
	the value is reset to a plain "grep" and is not useful.

groupcat (nis.U):
	This variable contains a command that produces the text of the
	/etc/group file.  This is normally "cat /etc/group", but can be
	"ypcat group" when NIS is used.
	On some systems, such as os390, there may be no equivalent
	command, in which case this variable is unset.

groupstype (groupstype.U):
	This variable defines Groups_t to be something like gid_t, int,
	ushort, or whatever type is used for the second argument to
	getgroups() and setgroups().  Usually, this is the same as
	gidtype (gid_t), but sometimes it isn't.

gzip (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the gzip program.  After Configure runs,
	the value is reset to a plain "gzip" and is not useful.

h_fcntl (h_fcntl.U):
	This is variable gets set in various places to tell i_fcntl that
	<fcntl.h> should be included.

h_sysfile (h_sysfile.U):
	This is variable gets set in various places to tell i_sys_file that
	<sys/file.h> should be included.

hint (Oldconfig.U):
	Gives the type of hints used for previous answers. May be one of
	"default", "recommended" or "previous".

hostcat (nis.U):
	This variable contains a command that produces the text of the
	/etc/hosts file.  This is normally "cat /etc/hosts", but can be
	"ypcat hosts" when NIS is used.
	On some systems, such as os390, there may be no equivalent
	command, in which case this variable is unset.

hostgenerate (Cross.U):
	This variable contains the path to a generate_uudmap binary that
	can be run on the host OS when cross-compiling.  Useful and
	available only during Perl build.
	Empty string '' if not cross-compiling.

hostosname (Cross.U):
	This variable contains the original value of '$^O' for hostperl
	when cross-compiling.  This is useful to pick the proper tools
	when running build code in the host.
	Empty string '' if not cross-compiling.

hostperl (Cross.U):
	This variable contains the path to a miniperl binary that can be
	run on the host OS when cross-compiling.  Useful and available only
	during Perl build.
	Empty string '' if not cross-compiling.

html1dir (html1dir.U):
	This variable contains the name of the directory in which html
	source pages are to be put.  This directory is for pages
	that describe whole programs, not libraries or modules.  It
	is intended to correspond roughly to section 1 of the Unix
	manuals.

html1direxp (html1dir.U):
	This variable is the same as the html1dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

html3dir (html3dir.U):
	This variable contains the name of the directory in which html
	source pages are to be put.  This directory is for pages
	that describe libraries or modules.  It is intended to
	correspond roughly to section 3 of the Unix manuals.

html3direxp (html3dir.U):
	This variable is the same as the html3dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

i16size (perlxv.U):
	This variable is the size of an I16 in bytes.

i16type (perlxv.U):
	This variable contains the C type used for Perl's I16.

i32dformat (perlx32f.U):
	This variable contains the format string used for printing
	a Perl I32 as a signed decimal integer.

i32size (perlxv.U):
	This variable is the size of an I32 in bytes.

i32type (perlxv.U):
	This variable contains the C type used for Perl's I32.

i64size (perlxv.U):
	This variable is the size of an I64 in bytes.

i64type (perlxv.U):
	This variable contains the C type used for Perl's I64.

i8size (perlxv.U):
	This variable is the size of an I8 in bytes.

i8type (perlxv.U):
	This variable contains the C type used for Perl's I8.

i_arpainet (i_arpainet.U):
	This variable conditionally defines the I_ARPA_INET symbol,
	and indicates whether a C program should include <arpa/inet.h>.

i_bfd (i_bfd.U):
	This variable conditionally defines the I_BFD symbol, and
	indicates whether a C program can include <bfd.h>.

i_bsdioctl (i_sysioctl.U):
	This variable conditionally defines the I_SYS_BSDIOCTL symbol, which
	indicates to the C program that <sys/bsdioctl.h> exists and should
	be included.

i_crypt (i_crypt.U):
	This variable conditionally defines the I_CRYPT symbol, and indicates
	whether a C program should include <crypt.h>.

i_db (i_db.U):
	This variable conditionally defines the I_DB symbol, and indicates
	whether a C program may include Berkeley's DB include file <db.h>.

i_dbm (i_dbm.U):
	This variable conditionally defines the I_DBM symbol, which
	indicates to the C program that <dbm.h> exists and should
	be included.

i_dirent (i_dirent.U):
	This variable conditionally defines I_DIRENT, which indicates
	to the C program that it should include <dirent.h>.

i_dlfcn (i_dlfcn.U):
	This variable conditionally defines the I_DLFCN symbol, which
	indicates to the C program that <dlfcn.h> exists and should
	be included.

i_execinfo (i_execinfo.U):
	This variable conditionally defines the I_EXECINFO symbol, and indicates
	whether a C program may include <execinfo.h>, for backtrace() support.

i_fcntl (i_fcntl.U):
	This variable controls the value of I_FCNTL (which tells
	the C program to include <fcntl.h>).

i_fenv (i_fenv.U):
	This variable conditionally defines the I_FENV symbol, which
	indicates to the C program that <fenv.h> exists and should
	be included.

i_fp (i_fp.U):
	This variable conditionally defines the I_FP symbol, and indicates
	whether a C program should include <fp.h>.

i_fp_class (i_fp_class.U):
	This variable conditionally defines the I_FP_CLASS symbol, and indicates
	whether a C program should include <fp_class.h>.

i_gdbm (i_gdbm.U):
	This variable conditionally defines the I_GDBM symbol, which
	indicates to the C program that <gdbm.h> exists and should
	be included.

i_gdbm_ndbm (i_ndbm.U):
	This variable conditionally defines the I_GDBM_NDBM symbol, which
	indicates to the C program that <gdbm-ndbm.h> exists and should
	be included.  This is the location of the ndbm.h compatibility file
	in Debian 4.0.

i_gdbmndbm (i_ndbm.U):
	This variable conditionally defines the I_GDBMNDBM symbol, which
	indicates to the C program that <gdbm/ndbm.h> exists and should
	be included.  This was the location of the ndbm.h compatibility file
	in RedHat 7.1.

i_grp (i_grp.U):
	This variable conditionally defines the I_GRP symbol, and indicates
	whether a C program should include <grp.h>.

i_ieeefp (i_ieeefp.U):
	This variable conditionally defines the I_IEEEFP symbol, and indicates
	whether a C program should include <ieeefp.h>.

i_inttypes (i_inttypes.U):
	This variable conditionally defines the I_INTTYPES symbol,
	and indicates whether a C program should include <inttypes.h>.

i_langinfo (i_langinfo.U):
	This variable conditionally defines the I_LANGINFO symbol,
	and indicates whether a C program should include <langinfo.h>.

i_libutil (i_libutil.U):
	This variable conditionally defines the I_LIBUTIL symbol, and indicates
	whether a C program should include <libutil.h>.

i_locale (i_locale.U):
	This variable conditionally defines the I_LOCALE symbol,
	and indicates whether a C program should include <locale.h>.

i_machcthr (i_machcthr.U):
	This variable conditionally defines the I_MACH_CTHREADS symbol,
	and indicates whether a C program should include <mach/cthreads.h>.

i_malloc (i_malloc.U):
	This variable conditionally defines the I_MALLOC symbol, and indicates
	whether a C program should include <malloc.h>.

i_mallocmalloc (i_mallocmalloc.U):
	This variable conditionally defines the I_MALLOCMALLOC symbol,
	and indicates whether a C program should include <malloc/malloc.h>.

i_mntent (i_mntent.U):
	This variable conditionally defines the I_MNTENT symbol, and indicates
	whether a C program should include <mntent.h>.

i_ndbm (i_ndbm.U):
	This variable conditionally defines the I_NDBM symbol, which
	indicates to the C program that <ndbm.h> exists and should
	be included.

i_netdb (i_netdb.U):
	This variable conditionally defines the I_NETDB symbol, and indicates
	whether a C program should include <netdb.h>.

i_neterrno (i_neterrno.U):
	This variable conditionally defines the I_NET_ERRNO symbol, which
	indicates to the C program that <net/errno.h> exists and should
	be included.

i_netinettcp (i_netinettcp.U):
	This variable conditionally defines the I_NETINET_TCP symbol,
	and indicates whether a C program should include <netinet/tcp.h>.

i_niin (i_niin.U):
	This variable conditionally defines I_NETINET_IN, which indicates
	to the C program that it should include <netinet/in.h>. Otherwise,
	you may try <sys/in.h>.

i_poll (i_poll.U):
	This variable conditionally defines the I_POLL symbol, and indicates
	whether a C program should include <poll.h>.

i_prot (i_prot.U):
	This variable conditionally defines the I_PROT symbol, and indicates
	whether a C program should include <prot.h>.

i_pthread (i_pthread.U):
	This variable conditionally defines the I_PTHREAD symbol,
	and indicates whether a C program should include <pthread.h>.

i_pwd (i_pwd.U):
	This variable conditionally defines I_PWD, which indicates
	to the C program that it should include <pwd.h>.

i_quadmath (i_quadmath.U):
	This variable conditionally defines I_QUADMATH, which indicates
	to the C program that it should include <quadmath.h>.

i_rpcsvcdbm (i_dbm.U):
	This variable conditionally defines the I_RPCSVC_DBM symbol, which
	indicates to the C program that <rpcsvc/dbm.h> exists and should
	be included.  Some System V systems might need this instead of <dbm.h>.

i_sgtty (i_termio.U):
	This variable conditionally defines the I_SGTTY symbol, which
	indicates to the C program that it should include <sgtty.h> rather
	than <termio.h>.

i_shadow (i_shadow.U):
	This variable conditionally defines the I_SHADOW symbol, and indicates
	whether a C program should include <shadow.h>.

i_socks (i_socks.U):
	This variable conditionally defines the I_SOCKS symbol, and indicates
	whether a C program should include <socks.h>.

i_stdbool (i_stdbool.U):
	This variable conditionally defines the I_STDBOOL symbol, which
	indicates to the C program that <stdbool.h> exists and should
	be included.

i_stdckdint (i_stdckdint.U):
	This variable conditionally defines the I_STDCKDINT symbol, which
	indicates to the C program that <stdckdint.h> exists and should
	be included.

i_stdint (i_stdint.U):
	This variable conditionally defines the I_STDINT symbol, which
	indicates to the C program that <stdint.h> exists and should
	be included.

i_stdlib (i_stdlib.U):
	This variable unconditionally defines the I_STDLIB symbol.

i_sunmath (i_sunmath.U):
	This variable conditionally defines the I_SUNMATH symbol, and indicates
	whether a C program should include <sunmath.h>.

i_sysaccess (i_sysaccess.U):
	This variable conditionally defines the I_SYS_ACCESS symbol,
	and indicates whether a C program should include <sys/access.h>.

i_sysdir (i_sysdir.U):
	This variable conditionally defines the I_SYS_DIR symbol, and indicates
	whether a C program should include <sys/dir.h>.

i_sysfile (i_sysfile.U):
	This variable conditionally defines the I_SYS_FILE symbol, and indicates
	whether a C program should include <sys/file.h> to get R_OK and friends.

i_sysfilio (i_sysioctl.U):
	This variable conditionally defines the I_SYS_FILIO symbol, which
	indicates to the C program that <sys/filio.h> exists and should
	be included in preference to <sys/ioctl.h>.

i_sysin (i_niin.U):
	This variable conditionally defines I_SYS_IN, which indicates
	to the C program that it should include <sys/in.h> instead of
	<netinet/in.h>.

i_sysioctl (i_sysioctl.U):
	This variable conditionally defines the I_SYS_IOCTL symbol, which
	indicates to the C program that <sys/ioctl.h> exists and should
	be included.

i_syslog (i_syslog.U):
	This variable conditionally defines the I_SYSLOG symbol,
	and indicates whether a C program should include <syslog.h>.

i_sysmman (i_sysmman.U):
	This variable conditionally defines the I_SYS_MMAN symbol,
	and indicates whether a C program should include <sys/mman.h>.

i_sysmode (i_sysmode.U):
	This variable conditionally defines the I_SYSMODE symbol,
	and indicates whether a C program should include <sys/mode.h>.

i_sysmount (i_sysmount.U):
	This variable conditionally defines the I_SYSMOUNT symbol,
	and indicates whether a C program should include <sys/mount.h>.

i_sysndir (i_sysndir.U):
	This variable conditionally defines the I_SYS_NDIR symbol, and indicates
	whether a C program should include <sys/ndir.h>.

i_sysparam (i_sysparam.U):
	This variable conditionally defines the I_SYS_PARAM symbol, and indicates
	whether a C program should include <sys/param.h>.

i_syspoll (i_syspoll.U):
	This variable conditionally defines the I_SYS_POLL symbol, which
	indicates to the C program that it should include <sys/poll.h>.

i_sysresrc (i_sysresrc.U):
	This variable conditionally defines the I_SYS_RESOURCE symbol,
	and indicates whether a C program should include <sys/resource.h>.

i_syssecrt (i_syssecrt.U):
	This variable conditionally defines the I_SYS_SECURITY symbol,
	and indicates whether a C program should include <sys/security.h>.

i_sysselct (i_sysselct.U):
	This variable conditionally defines I_SYS_SELECT, which indicates
	to the C program that it should include <sys/select.h> in order to
	get the definition of struct timeval.

i_syssockio (i_sysioctl.U):
	This variable conditionally defines I_SYS_SOCKIO to indicate to the
	C program that socket ioctl codes may be found in <sys/sockio.h>
	instead of <sys/ioctl.h>.

i_sysstat (i_sysstat.U):
	This variable conditionally defines the I_SYS_STAT symbol,
	and indicates whether a C program should include <sys/stat.h>.

i_sysstatfs (i_sysstatfs.U):
	This variable conditionally defines the I_SYSSTATFS symbol,
	and indicates whether a C program should include <sys/statfs.h>.

i_sysstatvfs (i_sysstatvfs.U):
	This variable conditionally defines the I_SYSSTATVFS symbol,
	and indicates whether a C program should include <sys/statvfs.h>.

i_syssyscall (i_syssyscall.U):
	This variable conditionally defines the I_SYS_SYSCALL symbol,
	and indicates whether a C program should include <sys/syscall.h>.

i_systime (i_time.U):
	This variable conditionally defines I_SYS_TIME, which indicates
	to the C program that it should include <sys/time.h>.

i_systimek (i_time.U):
	This variable conditionally defines I_SYS_TIME_KERNEL, which
	indicates to the C program that it should include <sys/time.h>
	with KERNEL defined.

i_systimes (i_systimes.U):
	This variable conditionally defines the I_SYS_TIMES symbol, and indicates
	whether a C program should include <sys/times.h>.

i_systypes (i_systypes.U):
	This variable conditionally defines the I_SYS_TYPES symbol,
	and indicates whether a C program should include <sys/types.h>.

i_sysuio (i_sysuio.U):
	This variable conditionally defines the I_SYSUIO symbol, and indicates
	whether a C program should include <sys/uio.h>.

i_sysun (i_sysun.U):
	This variable conditionally defines I_SYS_UN, which indicates
	to the C program that it should include <sys/un.h> to get UNIX
	domain socket definitions.

i_sysutsname (i_sysutsname.U):
	This variable conditionally defines the I_SYSUTSNAME symbol,
	and indicates whether a C program should include <sys/utsname.h>.

i_sysvfs (i_sysvfs.U):
	This variable conditionally defines the I_SYSVFS symbol,
	and indicates whether a C program should include <sys/vfs.h>.

i_syswait (i_syswait.U):
	This variable conditionally defines I_SYS_WAIT, which indicates
	to the C program that it should include <sys/wait.h>.

i_termio (i_termio.U):
	This variable conditionally defines the I_TERMIO symbol, which
	indicates to the C program that it should include <termio.h> rather
	than <sgtty.h>.

i_termios (i_termio.U):
	This variable conditionally defines the I_TERMIOS symbol, which
	indicates to the C program that the POSIX <termios.h> file is
	to be included.

i_time (i_time.U):
	This variable unconditionally defines I_TIME, which indicates
	to the C program that it should include <time.h>.

i_unistd (i_unistd.U):
	This variable conditionally defines the I_UNISTD symbol, and indicates
	whether a C program should include <unistd.h>.

i_ustat (i_ustat.U):
	This variable conditionally defines the I_USTAT symbol, and indicates
	whether a C program should include <ustat.h>.

i_utime (i_utime.U):
	This variable conditionally defines the I_UTIME symbol, and indicates
	whether a C program should include <utime.h>.

i_vfork (i_vfork.U):
	This variable conditionally defines the I_VFORK symbol, and indicates
	whether a C program should include vfork.h.

i_wchar (i_wchar.U):
	This variable conditionally defines the I_WCHAR symbol,
	that indicates whether a C program may include <wchar.h>.

i_wctype (i_wctype.U):
	This variable conditionally defines the I_WCTYPE symbol,
	that indicates whether a C program may include <wctype.h>.

i_xlocale (d_newlocale.U):
	This symbol, if defined, indicates to the C program that the
	header xlocale.h is available.  See also xlocale_needed.

ignore_versioned_solibs (libs.U):
	This variable should be non-empty if non-versioned shared
	libraries (libfoo.so.x.y) are to be ignored (because they
	cannot be linked against).

inc_version_list (inc_version_list.U):
	This variable specifies the list of subdirectories in over
	which perl.c:incpush() and lib/lib.pm will automatically
	search when adding directories to @INC.  The elements in
	the list are separated by spaces.  This is only useful
	if you have a perl library directory tree structured like the
	default one.  See INSTALL for how this works.  The versioned
	site_perl directory was introduced in 5.005, so that is the
	lowest possible value.

	This list includes architecture-dependent directories back to
	version $api_versionstring (e.g. 5.5.640) and
	architecture-independent directories all the way back to
	5.005.

inc_version_list_init (inc_version_list.U):
	This variable holds the same list as inc_version_list, but
	each item is enclosed in double quotes and separated by commas,
	suitable for use in the PERL_INC_VERSION_LIST initialization.

incpath (usrinc.U):
	This variable must precede the normal include path to get the
	right one, as in "$incpath/usr/include" or "$incpath/usr/lib".
	Value can be "" or "/bsd43" on mips.

incpth (libpth.U):
	This variable must precede the normal include path to get the
	right one, as in "$incpath/usr/include" or "$incpath/usr/lib".
	Value can be "" or "/bsd43" on mips.

inews (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

initialinstalllocation (bin.U):
	When userelocatableinc is true, this variable holds the location
	that make install should copy the perl binary to, with all the
	run-time relocatable paths calculated from this at install time.
	When used, it is initialized to the original value of binexp, and
	then binexp is set to '.../', as the other binaries are found
	relative to the perl binary.

installarchlib (archlib.U):
	This variable is really the same as archlibexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installbin (bin.U):
	This variable is the same as binexp unless AFS is running in which case
	the user is explicitly prompted for it. This variable should always
	be used in your makefiles for maximum portability.

installhtml1dir (html1dir.U):
	This variable is really the same as html1direxp, unless you are
	using a different installprefix.  For extra portability, you
	should only use this variable within your makefiles.

installhtml3dir (html3dir.U):
	This variable is really the same as html3direxp, unless you are
	using a different installprefix.  For extra portability, you
	should only use this variable within your makefiles.

installman1dir (man1dir.U):
	This variable is really the same as man1direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	man1direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installman3dir (man3dir.U):
	This variable is really the same as man3direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	man3direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installprefix (installprefix.U):
	This variable holds the name of the directory below which
	"make install" will install the package.  For most users, this
	is the same as prefix.  However, it is useful for
	installing the software into a different (usually temporary)
	location after which it can be bundled up and moved somehow
	to the final location specified by prefix.

installprefixexp (installprefix.U):
	This variable holds the full absolute path of installprefix
	with all ~-expansion done.

installprivlib (privlib.U):
	This variable is really the same as privlibexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installscript (scriptdir.U):
	This variable is usually the same as scriptdirexp, unless you are on
	a system running AFS, in which case they may differ slightly. You
	should always use this variable within your makefiles for portability.

installsitearch (sitearch.U):
	This variable is really the same as sitearchexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installsitebin (sitebin.U):
	This variable is usually the same as sitebinexp, unless you are on
	a system running AFS, in which case they may differ slightly. You
	should always use this variable within your makefiles for portability.

installsitehtml1dir (sitehtml1dir.U):
	This variable is really the same as sitehtml1direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	html1direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installsitehtml3dir (sitehtml3dir.U):
	This variable is really the same as sitehtml3direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	html3direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installsitelib (sitelib.U):
	This variable is really the same as sitelibexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installsiteman1dir (siteman1dir.U):
	This variable is really the same as siteman1direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	man1direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installsiteman3dir (siteman3dir.U):
	This variable is really the same as siteman3direxp, unless you are using
	AFS in which case it points to the read/write location whereas
	man3direxp only points to the read-only access location. For extra
	portability, you should only use this variable within your makefiles.

installsitescript (sitescript.U):
	This variable is usually the same as sitescriptexp, unless you are on
	a system running AFS, in which case they may differ slightly. You
	should always use this variable within your makefiles for portability.

installstyle (installstyle.U):
	This variable describes the "style" of the perl installation.
	This is intended to be useful for tools that need to
	manipulate entire perl distributions.  Perl itself doesn't use
	this to find its libraries -- the library directories are
	stored directly in Config.pm.  Currently, there are only two
	styles:  "lib" and "lib/perl5".  The default library locations
	(e.g. privlib, sitelib) are either $prefix/lib or
	$prefix/lib/perl5.  The former is useful if $prefix is a
	directory dedicated to perl (e.g. /opt/perl), while the latter
	is useful if $prefix is shared by many packages, e.g. if
	$prefix=/usr/local.

	Unfortunately, while this "style" variable is used to set
	defaults for all three directory hierarchies (core, vendor, and
	site), there is no guarantee that the same style is actually
	appropriate for all those directories.  For example, $prefix
	might be /opt/perl, but $siteprefix might be /usr/local.
	(Perhaps, in retrospect, the "lib" style should never have been
	supported, but it did seem like a nice idea at the time.)

	The situation is even less clear for tools such as MakeMaker
	that can be used to install additional modules into
	non-standard places.  For example, if a user intends to install
	a module into a private directory (perhaps by setting PREFIX on
	the Makefile.PL command line), then there is no reason to
	assume that the Configure-time $installstyle setting will be
	relevant for that PREFIX.

	This may later be extended to include other information, so
	be careful with pattern-matching on the results.

	For compatibility with perl5.005 and earlier, the default
	setting is based on whether or not $prefix contains the string
	"perl".

installusrbinperl (instubperl.U):
	This variable tells whether Perl should be installed also as
	/usr/bin/perl in addition to
	$installbin/perl

installvendorarch (vendorarch.U):
	This variable is really the same as vendorarchexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorbin (vendorbin.U):
	This variable is really the same as vendorbinexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorhtml1dir (vendorhtml1dir.U):
	This variable is really the same as vendorhtml1direxp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorhtml3dir (vendorhtml3dir.U):
	This variable is really the same as vendorhtml3direxp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorlib (vendorlib.U):
	This variable is really the same as vendorlibexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorman1dir (vendorman1dir.U):
	This variable is really the same as vendorman1direxp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorman3dir (vendorman3dir.U):
	This variable is really the same as vendorman3direxp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

installvendorscript (vendorscript.U):
	This variable is really the same as vendorscriptexp but may differ on
	those systems using AFS. For extra portability, only this variable
	should be used in makefiles.

intsize (intsize.U):
	This variable contains the value of the INTSIZE symbol, which
	indicates to the C program how many bytes there are in an int.

issymlink (issymlink.U):
	This variable holds the test command to test for a symbolic link
	(if they are supported).  Typical values include 'test -h' and
	'test -L'.

ivdformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl IV as a signed decimal integer.

ivsize (perlxv.U):
	This variable is the size of an IV in bytes.

ivtype (perlxv.U):
	This variable contains the C type used for Perl's IV.

known_extensions (Extensions.U):
	This variable holds a list of all extensions (both XS and non-xs)
	included in the package source distribution.  This information is
	only really of use during the Perl build, as the list makes no
	distinction between extensions which were build and installed, and
	those which where not.  See "extensions" for the list of extensions
	actually built and available.

ksh (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

ld (dlsrc.U):
	This variable indicates the program to be used to link
	libraries for dynamic loading.  On some systems, it is 'ld'.
	On ELF systems, it should be $cc.  Mostly, we'll try to respect
	the hint file setting.

ld_can_script (dlsrc.U):
	This variable shows if the loader accepts scripts in the form of
	-Wl,--version-script=ld.script. This is currently only supported
	for GNU ld on ELF in dynamic loading builds.

lddlflags (dlsrc.U):
	This variable contains any special flags that might need to be
	passed to $ld to create a shared library suitable for dynamic
	loading.  It is up to the makefile to use it.  For hpux, it
	should be '-b'.  For sunos 4.1, it is empty.

ldflags (ccflags.U):
	This variable contains any additional C loader flags desired by
	the user.  It is up to the Makefile to use this.

ldflags_uselargefiles (uselfs.U):
	This variable contains the loader flags needed by large file builds
	and added to ldflags by hints files.

ldlibpthname (libperl.U):
	This variable holds the name of the shared library
	search path, often LD_LIBRARY_PATH.  To get an empty
	string, the hints file must set this to 'none'.

less (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the less program.  After Configure runs,
	the value is reset to a plain "less" and is not useful.

lib_ext (Unix.U):
	This is an old synonym for _a.

libc (libc.U):
	This variable contains the location of the C library.

libperl (libperl.U):
	The perl executable is obtained by linking perlmain.c with
	libperl, any static extensions (usually just DynaLoader),
	and any other libraries needed on this system.  libperl
	is usually libperl.a, but can also be libperl.so.xxx if
	the user wishes to build a perl executable with a shared
	library.

libpth (libpth.U):
	This variable holds the general path (space-separated) used to find
	libraries. It is intended to be used by other units.

libs (libs.U):
	This variable holds the additional libraries we want to use.
	It is up to the Makefile to deal with it.  The list can be empty.

libsdirs (libs.U):
	This variable holds the directory names aka dirnames of the libraries
	we found and accepted, duplicates are removed.

libsfiles (libs.U):
	This variable holds the filenames aka basenames of the libraries
	we found and accepted.

libsfound (libs.U):
	This variable holds the full pathnames of the libraries
	we found and accepted.

libspath (libs.U):
	This variable holds the directory names probed for libraries.

libswanted (Myinit.U):
	This variable holds a list of all the libraries we want to
	search.  The order is chosen to pick up the c library
	ahead of ucb or bsd libraries for SVR4.

libswanted_uselargefiles (uselfs.U):
	This variable contains the libraries needed by large file builds
	and added to ldflags by hints files.  It is a space separated list
	of the library names without the "lib" prefix or any suffix, just
	like libswanted..

line (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

lint (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

lkflags (ccflags.U):
	This variable contains any additional C partial linker flags desired by
	the user.  It is up to the Makefile to use this.

ln (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the ln program.  After Configure runs,
	the value is reset to a plain "ln" and is not useful.

lns (lns.U):
	This variable holds the name of the command to make
	symbolic links (if they are supported).  It can be used
	in the Makefile. It is either 'ln -s' or 'ln'

localtime_r_proto (d_localtime_r.U):
	This variable encodes the prototype of localtime_r.
	It is zero if d_localtime_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_localtime_r
	is defined.

locincpth (ccflags.U):
	This variable contains a list of additional directories to be
	searched by the compiler.  The appropriate '-I' directives will
	be added to ccflags.  This is intended to simplify setting
	local directories from the Configure command line.
	It's not much, but it parallels the loclibpth stuff in libpth.U.

loclibpth (libpth.U):
	This variable holds the paths (space-separated) used to find local
	libraries.  It is prepended to libpth, and is intended to be easily
	set from the command line.

longdblinfbytes (infnan.U):
	This variable contains comma-separated list of hexadecimal bytes
	for the long double precision infinity.

longdblkind (d_longdbl.U):
	This variable, if defined, encodes the type of a long double:
	0 = double,
	1 = IEEE 754 128-bit little endian,
	2 = IEEE 754 128-bit big endian,
	3 = x86 80-bit little endian,
	4 = x86 80-bit big endian,
	5 = double-double 128-bit little endian,
	6 = double-double 128-bit big endian,
	7 = 128-bit mixed-endian double-double (64-bit LEs in BE),
	8 = 128-bit mixed-endian double-double (64-bit BEs in LE),
	9 = 128-bit PDP-style mixed-endian long doubles,
	-1 = unknown format.

longdblmantbits (mantbits.U):
	This symbol, if defined, tells how many mantissa bits
	there are in long double precision floating point format.
	Note that this can be LDBL_MANT_DIG minus one,
	since LDBL_MANT_DIG can include the IEEE 754 implicit bit.
	The common x86-style 80-bit long double does not have
	an implicit bit.

longdblnanbytes (infnan.U):
	This variable contains comma-separated list of hexadecimal bytes
	for the long double precision not-a-number.

longdblsize (d_longdbl.U):
	This variable contains the value of the LONG_DOUBLESIZE symbol, which
	indicates to the C program how many bytes there are in a long double,
	if this system supports long doubles.  Note that this is
	sizeof(long double), which may include unused bytes.

longlongsize (d_longlong.U):
	This variable contains the value of the LONGLONGSIZE symbol, which
	indicates to the C program how many bytes there are in a long long,
	if this system supports long long.

longsize (intsize.U):
	This variable contains the value of the LONGSIZE symbol, which
	indicates to the C program how many bytes there are in a long.

lp (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

lpr (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

ls (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the ls program.  After Configure runs,
	the value is reset to a plain "ls" and is not useful.

lseeksize (lseektype.U):
	This variable defines lseektype to be something like off_t, long,
	or whatever type is used to declare lseek offset's type in the
	kernel (which also appears to be lseek's return type).

lseektype (lseektype.U):
	This variable defines lseektype to be something like off_t, long,
	or whatever type is used to declare lseek offset's type in the
	kernel (which also appears to be lseek's return type).

mail (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

mailx (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

make (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the make program.  After Configure runs,
	the value is reset to a plain "make" and is not useful.

make_set_make (make.U):
	Some versions of 'make' set the variable MAKE.  Others do not.
	This variable contains the string to be included in Makefile.SH
	so that MAKE is set if needed, and not if not needed.
	Possible values are:

	make_set_make='#'		# If your make program handles this for you,

	make_set_make="MAKE=$make"	# if it doesn't.

	This uses a comment character so that we can distinguish a
	'set' value (from a previous config.sh or Configure '-D' option)
	from an uncomputed value.

mallocobj (mallocsrc.U):
	This variable contains the name of the malloc.o that this package
	generates, if that malloc.o is preferred over the system malloc.
	Otherwise the value is null.  This variable is intended for generating
	Makefiles.  See mallocsrc.

mallocsrc (mallocsrc.U):
	This variable contains the name of the malloc.c that comes with
	the package, if that malloc.c is preferred over the system malloc.
	Otherwise the value is null.  This variable is intended for generating
	Makefiles.

malloctype (mallocsrc.U):
	This variable contains the kind of ptr returned by malloc and realloc.

man1dir (man1dir.U):
	This variable contains the name of the directory in which manual
	source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.

man1direxp (man1dir.U):
	This variable is the same as the man1dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

man1ext (man1dir.U):
	This variable contains the extension that the manual page should
	have: one of 'n', 'l', or '1'.  The Makefile must supply the '.'.
	See man1dir.

man3dir (man3dir.U):
	This variable contains the name of the directory in which manual
	source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.

man3direxp (man3dir.U):
	This variable is the same as the man3dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

man3ext (man3dir.U):
	This variable contains the extension that the manual page should
	have: one of 'n', 'l', or '3'.  The Makefile must supply the '.'.
	See man3dir.

mips_type (usrinc.U):
	This variable holds the environment type for the mips system.
	Possible values are "BSD 4.3" and "System V".

mistrustnm (Csym.U):
	This variable can be used to establish a fallthrough for the cases
	where nm fails to find a symbol.  If usenm is false or usenm is true
	and mistrustnm is false, this variable has no effect.  If usenm is true
	and mistrustnm is "compile", a test program will be compiled to try to
	find any symbol that can't be located via nm lookup.  If mistrustnm is
	"run", the test program will be run as well as being compiled.

mkdir (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the mkdir program.  After Configure runs,
	the value is reset to a plain "mkdir" and is not useful.

mmaptype (d_mmap.U):
	This symbol contains the type of pointer returned by mmap()
	(and simultaneously the type of the first argument).
	It can be 'void *' or 'caddr_t'.

modetype (modetype.U):
	This variable defines modetype to be something like mode_t,
	int, unsigned short, or whatever type is used to declare file
	modes for system calls.

more (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the more program.  After Configure runs,
	the value is reset to a plain "more" and is not useful.

multiarch (multiarch.U):
	This variable conditionally defines the MULTIARCH symbol
	which signifies the presence of multiplatform files.
	This is normally set by hints files.

mv (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

myarchname (archname.U):
	This variable holds the architecture name computed by Configure in
	a previous run. It is not intended to be perused by any user and
	should never be set in a hint file.

mydomain (myhostname.U):
	This variable contains the eventual value of the MYDOMAIN symbol,
	which is the domain of the host the program is going to run on.
	The domain must be appended to myhostname to form a complete host name.
	The dot comes with mydomain, and need not be supplied by the program.

myhostname (myhostname.U):
	This variable contains the eventual value of the MYHOSTNAME symbol,
	which is the name of the host the program is going to run on.
	The domain is not kept with hostname, but must be gotten from mydomain.
	The dot comes with mydomain, and need not be supplied by the program.

myuname (Oldconfig.U):
	The output of 'uname -a' if available, otherwise the hostname.
	The whole thing is then lower-cased and slashes and single quotes are
	removed.

n (n.U):
	This variable contains the '-n' flag if that is what causes the echo
	command to suppress newline.  Otherwise it is null.  Correct usage is
	$echo $n "prompt for a question: $c".

need_va_copy (need_va_copy.U):
	This symbol, if defined, indicates that the system stores
	the variable argument list datatype, va_list, in a format
	that cannot be copied by simple assignment, so that some
	other means must be used when copying is required.
	As such systems vary in their provision (or non-provision)
	of copying mechanisms, handy.h defines a platform-
	independent macro, Perl_va_copy(src, dst), to do the job.

netdb_hlen_type (netdbtype.U):
	This variable holds the type used for the 2nd argument to
	gethostbyaddr().  Usually, this is int or size_t or unsigned.
	This is only useful if you have gethostbyaddr(), naturally.

netdb_host_type (netdbtype.U):
	This variable holds the type used for the 1st argument to
	gethostbyaddr().  Usually, this is char * or void *,  possibly
	with or without a const prefix.
	This is only useful if you have gethostbyaddr(), naturally.

netdb_name_type (netdbtype.U):
	This variable holds the type used for the argument to
	gethostbyname().  Usually, this is char * or const char *.
	This is only useful if you have gethostbyname(), naturally.

netdb_net_type (netdbtype.U):
	This variable holds the type used for the 1st argument to
	getnetbyaddr().  Usually, this is int or long.
	This is only useful if you have getnetbyaddr(), naturally.

nm (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the nm program.  After Configure runs,
	the value is reset to a plain "nm" and is not useful.

nm_opt (usenm.U):
	This variable holds the options that may be necessary for nm.

nm_so_opt (usenm.U):
	This variable holds the options that may be necessary for nm
	to work on a shared library but that can not be used on an
	archive library.  Currently, this is only used by Linux, where
	nm --dynamic is *required* to get symbols from an ELF library which
	has been stripped, but nm --dynamic is *fatal* on an archive library.
	Maybe Linux should just always set usenm=false.

nonxs_ext (Extensions.U):
	This variable holds a list of all non-xs extensions built and
	installed by the package.  By default, all non-xs extensions
	distributed will be built, with the exception of platform-specific
	extensions (currently only one VMS specific extension).

nroff (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the nroff program.  After Configure runs,
	the value is reset to a plain "nroff" and is not useful.

nv_overflows_integers_at (perlxv.U):
	This variable gives the largest integer value that NVs can hold
	as a constant floating point expression.
	If it could not be determined, it holds the value 0.

nv_preserves_uv_bits (perlxv.U):
	This variable indicates how many of bits type uvtype
	a variable nvtype can preserve.

nveformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %e-ish floating point format.

nvEUformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %E-ish floating point format.

nvfformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %f-ish floating point format.

nvFUformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %F-ish floating point format.

nvgformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %g-ish floating point format.

nvGUformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl NV using %G-ish floating point format.

nvmantbits (mantbits.U):
	This variable tells how many bits the mantissa of a Perl NV has,
	not including the possible implicit bit.

nvsize (perlxv.U):
	This variable is the size of a Perl NV in bytes.
	Note that some floating point formats have unused bytes.

nvtype (perlxv.U):
	This variable contains the C type used for Perl's NV.

o_nonblock (nblock_io.U):
	This variable bears the symbol value to be used during open() or fcntl()
	to turn on non-blocking I/O for a file descriptor. If you wish to switch
	between blocking and non-blocking, you may try ioctl(FIOSNBIO) instead,
	but that is only supported by some devices.

obj_ext (Unix.U):
	This is an old synonym for _o.

old_pthread_create_joinable (d_pthrattrj.U):
	This variable defines the constant to use for creating joinable
	(aka undetached) pthreads.  Unused if pthread.h defines
	PTHREAD_CREATE_JOINABLE.  If used, possible values are
	PTHREAD_CREATE_UNDETACHED and __UNDETACHED.

optimize (ccflags.U):
	This variable contains any optimizer/debugger flag that should be used.
	It is up to the Makefile to use it.

orderlib (orderlib.U):
	This variable is "true" if the components of libraries must be ordered
	(with `lorder $* | tsort`) before placing them in an archive.  Set to
	"false" if ranlib or ar can generate random libraries.

osname (Oldconfig.U):
	This variable contains the operating system name (e.g. sunos,
	solaris, hpux, etc.).  It can be useful later on for setting
	defaults.  Any spaces are replaced with underscores.  It is set
	to a null string if we can't figure it out.

osvers (Oldconfig.U):
	This variable contains the operating system version (e.g.
	4.1.3, 5.2, etc.).  It is primarily used for helping select
	an appropriate hints file, but might be useful elsewhere for
	setting defaults.  It is set to '' if we can't figure it out.
	We try to be flexible about how much of the version number
	to keep, e.g. if 4.1.1, 4.1.2, and 4.1.3 are essentially the
	same for this package, hints files might just be os_4.0 or
	os_4.1, etc., not keeping separate files for each little release.

otherlibdirs (otherlibdirs.U):
	This variable contains a colon-separated set of paths for the perl
	binary to search for additional library files or modules.
	These directories will be tacked to the end of @INC.
	Perl will automatically search below each path for version-
	and architecture-specific directories.  See inc_version_list
	for more details.
	A value of ' ' means 'none' and is used to preserve this value
	for the next run through Configure.

package (package.U):
	This variable contains the name of the package being constructed.
	It is primarily intended for the use of later Configure units.

pager (pager.U):
	This variable contains the name of the preferred pager on the system.
	Usual values are (the full pathnames of) more, less, pg, or cat.

passcat (nis.U):
	This variable contains a command that produces the text of the
	/etc/passwd file.  This is normally "cat /etc/passwd", but can be
	"ypcat passwd" when NIS is used.
	On some systems, such as os390, there may be no equivalent
	command, in which case this variable is unset.

patchlevel (patchlevel.U):
	The patchlevel level of this package.
	The value of patchlevel comes from the patchlevel.h file.
	In a version number such as 5.6.1, this is the "6".
	In patchlevel.h, this is referred to as "PERL_VERSION".

path_sep (Unix.U):
	This is an old synonym for p_ in Head.U, the character
	used to separate elements in the command shell search PATH.

perl (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the perl program.  After Configure runs,
	the value is reset to a plain "perl" and is not useful.

perl5 (perl5.U):
	This variable contains the full path (if any) to a previously
	installed perl5.005 or later suitable for running the script
	to determine inc_version_list.

PERL_API_REVISION (patchlevel.h):
	This number describes the earliest compatible PERL_REVISION of
	Perl ("compatibility" here being defined as sufficient binary/API
	compatibility to run XS code built with the older version).
	Normally this does not change across maintenance releases.
	Please read the comment in patchlevel.h.

PERL_API_SUBVERSION (patchlevel.h):
	This number describes the earliest compatible PERL_SUBVERSION of
	Perl ("compatibility" here being defined as sufficient binary/API
	compatibility to run XS code built with the older version).
	Normally this does not change across maintenance releases.
	Please read the comment in patchlevel.h.

PERL_API_VERSION (patchlevel.h):
	This number describes the earliest compatible PERL_VERSION of
	Perl ("compatibility" here being defined as sufficient binary/API
	compatibility to run XS code built with the older version).
	Normally this does not change across maintenance releases.
	Please read the comment in patchlevel.h.

PERL_CONFIG_SH (Oldsyms.U):
	This is set to 'true' in config.sh so that a shell script
	sourcing config.sh can tell if it has been sourced already.

perl_lc_all_category_positions_init (disparate_lc_all.U):
	This symbol, when defined, gives the C initializer for an array whose
	element [0] is the first category in the string returned by
	setlocale(LC_ALL, NULL) when not all categories are the same, on
	systems that use a positional notation.  After element [0] is
	$lc_all_separator_init, then the category given by element [1], and so on.

perl_lc_all_separator (disparate_lc_all.U):
	This symbol, when defined, gives the substring used to separate
	categories in the aggregated string returned by setlocale(LC_ALL, NULL)
	when not all categories are in the same locale.  This is for systems
	that use a positional notation as opposed to 'name=value' pairs.

PERL_PATCHLEVEL (Oldsyms.U):
	This symbol reflects the patchlevel, if available. Will usually
	come from the .patch file, which is available when the perl
	source tree was fetched with rsync.

perl_patchlevel (patchlevel.U):
	This is the Perl patch level, a numeric change identifier,
	as defined by whichever source code maintenance system
	is used to maintain the patches; currently Perforce.
	It does not correlate with the Perl version numbers or
	the maintenance versus development dichotomy except
	by also being increasing.

PERL_REVISION (Oldsyms.U):
	In a Perl version number such as 5.6.2, this is the 5.
	This value is manually set in patchlevel.h

perl_static_inline (d_static_inline.U):
	This variable defines the PERL_STATIC_INLINE symbol to
	the best-guess incantation to use for static inline functions.
	Possibilities include
	static inline       (c99)
	static __inline__   (gcc -ansi)
	static __inline     (MSVC)
	static _inline      (older MSVC)
	static              (c89 compilers)

PERL_SUBVERSION (Oldsyms.U):
	In a Perl version number such as 5.6.2, this is the 2.
	Values greater than 50 represent potentially unstable
	development subversions.
	This value is manually set in patchlevel.h

perl_thread_local (d_thread_local.U):
	This variable gives the value for the PERL_THREAD_LOCAL symbol (when
	defined), which gives a linkage specification for thread-local storage.

PERL_VERSION (Oldsyms.U):
	In a Perl version number such as 5.6.2, this is the 6.
	This value is manually set in patchlevel.h

perladmin (perladmin.U):
	Electronic mail address of the perl5 administrator.

perllibs (End.U):
	The list of libraries needed by Perl only (any libraries needed
	by extensions only will by dropped, if using dynamic loading).

perlpath (perlpath.U):
	This variable contains the eventual value of the PERLPATH symbol,
	which contains the name of the perl interpreter to be used in
	shell scripts and in the "eval 'exec'" idiom.  This variable is
	not necessarily the pathname of the file containing the perl
	interpreter; you must append the executable extension (_exe) if
	it is not already present.  Note that Perl code that runs during
	the Perl build process cannot reference this variable, as Perl
	may not have been installed, or even if installed, may be a
	different version of Perl.

pg (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the pg program.  After Configure runs,
	the value is reset to a plain "pg" and is not useful.

phostname (myhostname.U):
	This variable contains the eventual value of the PHOSTNAME symbol,
	which is a command that can be fed to popen() to get the host name.
	The program should probably not presume that the domain is or isn't
	there already.

pidtype (pidtype.U):
	This variable defines PIDTYPE to be something like pid_t, int,
	ushort, or whatever type is used to declare process ids in the kernel.

plibpth (libpth.U):
	Holds the private path used by Configure to find out the libraries.
	Its value is prepend to libpth. This variable takes care of special
	machines, like the mips.  Usually, it should be empty.

pmake (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

pr (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

prefix (prefix.U):
	This variable holds the name of the directory below which the
	user will install the package.  Usually, this is /usr/local, and
	executables go in /usr/local/bin, library stuff in /usr/local/lib,
	man pages in /usr/local/man, etc.  It is only used to set defaults
	for things in bin.U, mansrc.U, privlib.U, or scriptdir.U.

prefixexp (prefix.U):
	This variable holds the full absolute path of the directory below
	which the user will install the package.  Derived from prefix.

privlib (privlib.U):
	This variable contains the eventual value of the PRIVLIB symbol,
	which is the name of the private library for this package.  It may
	have a ~ on the front. It is up to the makefile to eventually create
	this directory while performing installation (with ~ substitution).

privlibexp (privlib.U):
	This variable is the ~name expanded version of privlib, so that you
	may use it directly in Makefiles or shell scripts.

procselfexe (d_procselfexe.U):
	If d_procselfexe is defined, $procselfexe is the filename
	of the symbolic link pointing to the absolute pathname of
	the executing program.

ptrsize (ptrsize.U):
	This variable contains the value of the PTRSIZE symbol, which
	indicates to the C program how many bytes there are in a pointer.

quadkind (quadtype.U):
	This variable, if defined, encodes the type of a quad:
	1 = int, 2 = long, 3 = long long, 4 = int64_t.

quadtype (quadtype.U):
	This variable defines Quad_t to be something like long, int,
	long long, int64_t, or whatever type is used for 64-bit integers.

randbits (randfunc.U):
	Indicates how many bits are produced by the function used to
	generate normalized random numbers.

randfunc (randfunc.U):
	Indicates the name of the random number function to use.
	Values include drand48, random, and rand. In C programs,
	the 'Drand01' macro is defined to generate uniformly distributed
	random numbers over the range [0., 1.[ (see drand01 and nrand).

random_r_proto (d_random_r.U):
	This variable encodes the prototype of random_r.
	It is zero if d_random_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_random_r
	is defined.

randseedtype (randfunc.U):
	Indicates the type of the argument of the seedfunc.

ranlib (orderlib.U):
	This variable is set to the pathname of the ranlib program, if it is
	needed to generate random libraries.  Set to ":" if ar can generate
	random libraries or if random libraries are not supported

rd_nodata (nblock_io.U):
	This variable holds the return code from read() when no data is
	present. It should be -1, but some systems return 0 when O_NDELAY is
	used, which is a shame because you cannot make the difference between
	no data and an EOF.. Sigh!

readdir64_r_proto (d_readdir64_r.U):
	This variable encodes the prototype of readdir64_r.
	It is zero if d_readdir64_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_readdir64_r
	is defined.

readdir_r_proto (d_readdir_r.U):
	This variable encodes the prototype of readdir_r.
	It is zero if d_readdir_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_readdir_r
	is defined.

revision (patchlevel.U):
	The value of revision comes from the patchlevel.h file.
	In a version number such as 5.6.1, this is the "5".
	In patchlevel.h, this is referred to as "PERL_REVISION".

rm (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the rm program.  After Configure runs,
	the value is reset to a plain "rm" and is not useful.

rm_try (Unix.U):
	This is a cleanup variable for try test programs.
	Internal Configure use only.

rmail (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

run (Cross.U):
	This variable contains the command used by Configure
	to copy and execute a cross-compiled executable in the
	target host.  Useful and available only during Perl build.
	Empty string '' if not cross-compiling.

runnm (usenm.U):
	This variable contains 'true' or 'false' depending whether the
	nm extraction should be performed or not, according to the value
	of usenm and the flags on the Configure command line.

sched_yield (d_pthread_y.U):
	This variable defines the way to yield the execution
	of the current thread.

scriptdir (scriptdir.U):
	This variable holds the name of the directory in which the user wants
	to put publicly scripts for the package in question.  It is either
	the same directory as for binaries, or a special one that can be
	mounted across different architectures, like /usr/share. Programs
	must be prepared to deal with ~name expansion.

scriptdirexp (scriptdir.U):
	This variable is the same as scriptdir, but is filename expanded
	at configuration time, for programs not wanting to bother with it.

sed (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the sed program.  After Configure runs,
	the value is reset to a plain "sed" and is not useful.

seedfunc (randfunc.U):
	Indicates the random number generating seed function.
	Values include srand48, srandom, and srand.

selectminbits (selectminbits.U):
	This variable holds the minimum number of bits operated by select.
	That is, if you do select(n, ...), how many bits at least will be
	cleared in the masks if some activity is detected.  Usually this
	is either n or 32*ceil(n/32), especially many little-endians do
	the latter.  This is only useful if you have select(), naturally.

selecttype (selecttype.U):
	This variable holds the type used for the 2nd, 3rd, and 4th
	arguments to select.  Usually, this is 'fd_set *', if HAS_FD_SET
	is defined, and 'int *' otherwise.  This is only useful if you
	have select(), naturally.

sendmail (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

setgrent_r_proto (d_setgrent_r.U):
	This variable encodes the prototype of setgrent_r.
	It is zero if d_setgrent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setgrent_r
	is defined.

sethostent_r_proto (d_sethostent_r.U):
	This variable encodes the prototype of sethostent_r.
	It is zero if d_sethostent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_sethostent_r
	is defined.

setlocale_r_proto (d_setlocale_r.U):
	This variable encodes the prototype of setlocale_r.
	It is zero if d_setlocale_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setlocale_r
	is defined.

setnetent_r_proto (d_setnetent_r.U):
	This variable encodes the prototype of setnetent_r.
	It is zero if d_setnetent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setnetent_r
	is defined.

setprotoent_r_proto (d_setprotoent_r.U):
	This variable encodes the prototype of setprotoent_r.
	It is zero if d_setprotoent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setprotoent_r
	is defined.

setpwent_r_proto (d_setpwent_r.U):
	This variable encodes the prototype of setpwent_r.
	It is zero if d_setpwent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setpwent_r
	is defined.

setservent_r_proto (d_setservent_r.U):
	This variable encodes the prototype of setservent_r.
	It is zero if d_setservent_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_setservent_r
	is defined.

sGMTIME_max (time_size.U):
	This variable defines the maximum value of the time_t offset that
	the system function gmtime () accepts

sGMTIME_min (time_size.U):
	This variable defines the minimum value of the time_t offset that
	the system function gmtime () accepts

sh (sh.U):
	This variable contains the full pathname of the shell used
	on this system to execute Bourne shell scripts.  Usually, this will be
	/bin/sh, though it's possible that some systems will have /bin/ksh,
	/bin/pdksh, /bin/ash, /bin/bash, or even something such as
	D:/bin/sh.exe.
	This unit comes before Options.U, so you can't set sh with a '-D'
	option, though you can override this (and startsh)
	with '-O -Dsh=/bin/whatever -Dstartsh=whatever'

shar (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

sharpbang (spitshell.U):
	This variable contains the string #! if this system supports that
	construct.

shmattype (d_shmat.U):
	This symbol contains the type of pointer returned by shmat().
	It can be 'void *' or 'char *'.

shortsize (intsize.U):
	This variable contains the value of the SHORTSIZE symbol which
	indicates to the C program how many bytes there are in a short.

shrpenv (libperl.U):
	If the user builds a shared libperl.so, then we need to tell the
	'perl' executable where it will be able to find the installed libperl.so.
	One way to do this on some systems is to set the environment variable
	LD_RUN_PATH to the directory that will be the final location of the
	shared libperl.so.  The makefile can use this with something like
	$shrpenv $(CC) -o perl perlmain.o $libperl $libs
	Typical values are
	shrpenv="env LD_RUN_PATH=$archlibexp/CORE"
	or
	shrpenv=''
	See the main perl Makefile.SH for actual working usage.

	Alternatively, we might be able to use a command line option such
	as -R $archlibexp/CORE (Solaris) or -Wl,-rpath
	$archlibexp/CORE (Linux).

shsharp (spitshell.U):
	This variable tells further Configure units whether your sh can
	handle # comments.

sig_count (sig_name.U):
	This variable holds a number larger than the largest valid
	signal number.  This is usually the same as the NSIG macro.

sig_name (sig_name.U):
	This variable holds the signal names, space separated. The leading
	SIG in signal name is removed.  A ZERO is prepended to the list.
	This is currently not used, sig_name_init is used instead.

sig_name_init (sig_name.U):
	This variable holds the signal names, enclosed in double quotes and
	separated by commas, suitable for use in the SIG_NAME definition
	below.  A "ZERO" is prepended to the list, and the list is
	terminated with a plain 0.  The leading SIG in signal names
	is removed. See sig_num.

sig_num (sig_name.U):
	This variable holds the signal numbers, space separated. A ZERO is
	prepended to the list (corresponding to the fake SIGZERO).
	Those numbers correspond to  the value of the signal listed
	in the same place within the sig_name list.
	This is currently not used, sig_num_init is used instead.

sig_num_init (sig_name.U):
	This variable holds the signal numbers, enclosed in double quotes and
	separated by commas, suitable for use in the SIG_NUM definition
	below.  A "ZERO" is prepended to the list, and the list is
	terminated with a plain 0.

sig_size (sig_name.U):
	This variable contains the number of elements of the sig_name
	and sig_num arrays.

signal_t (d_voidsig.U):
	This variable holds the type of the signal handler (void or int).

sitearch (sitearch.U):
	This variable contains the eventual value of the SITEARCH symbol,
	which is the name of the private library for this package.  It may
	have a ~ on the front. It is up to the makefile to eventually create
	this directory while performing installation (with ~ substitution).
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	architecture-dependent modules in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitearchexp (sitearch.U):
	This variable is the ~name expanded version of sitearch, so that you
	may use it directly in Makefiles or shell scripts.

sitebin (sitebin.U):
	This variable holds the name of the directory in which the user wants
	to put add-on publicly executable files for the package in question.  It
	is most often a local directory such as /usr/local/bin. Programs using
	this variable must be prepared to deal with ~name substitution.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	executables in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitebinexp (sitebin.U):
	This is the same as the sitebin variable, but is filename expanded at
	configuration time, for use in your makefiles.

sitehtml1dir (sitehtml1dir.U):
	This variable contains the name of the directory in which site-specific
	html source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	html pages in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitehtml1direxp (sitehtml1dir.U):
	This variable is the same as the sitehtml1dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

sitehtml3dir (sitehtml3dir.U):
	This variable contains the name of the directory in which site-specific
	library html source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	library html pages in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitehtml3direxp (sitehtml3dir.U):
	This variable is the same as the sitehtml3dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

sitelib (sitelib.U):
	This variable contains the eventual value of the SITELIB symbol,
	which is the name of the private library for this package.  It may
	have a ~ on the front. It is up to the makefile to eventually create
	this directory while performing installation (with ~ substitution).
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	architecture-independent modules in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitelib_stem (sitelib.U):
	This variable is $sitelibexp with any trailing version-specific component
	removed.  The elements in inc_version_list (inc_version_list.U) can
	be tacked onto this variable to generate a list of directories to search.

sitelibexp (sitelib.U):
	This variable is the ~name expanded version of sitelib, so that you
	may use it directly in Makefiles or shell scripts.

siteman1dir (siteman1dir.U):
	This variable contains the name of the directory in which site-specific
	manual source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	man1 pages in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

siteman1direxp (siteman1dir.U):
	This variable is the same as the siteman1dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

siteman3dir (siteman3dir.U):
	This variable contains the name of the directory in which site-specific
	library man source pages are to be put.  It is the responsibility of the
	Makefile.SH to get the value of this into the proper command.
	You must be prepared to do the ~name expansion yourself.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	man3 pages in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

siteman3direxp (siteman3dir.U):
	This variable is the same as the siteman3dir variable, but is filename
	expanded at configuration time, for convenient use in makefiles.

siteprefix (siteprefix.U):
	This variable holds the full absolute path of the directory below
	which the user will install add-on packages.
	See INSTALL for usage and examples.

siteprefixexp (siteprefix.U):
	This variable holds the full absolute path of the directory below
	which the user will install add-on packages.  Derived from siteprefix.

sitescript (sitescript.U):
	This variable holds the name of the directory in which the user wants
	to put add-on publicly executable files for the package in question.  It
	is most often a local directory such as /usr/local/bin. Programs using
	this variable must be prepared to deal with ~name substitution.
	The standard distribution will put nothing in this directory.
	After perl has been installed, users may install their own local
	scripts in this directory with
	MakeMaker Makefile.PL
	or equivalent.  See INSTALL for details.

sitescriptexp (sitescript.U):
	This is the same as the sitescript variable, but is filename expanded at
	configuration time, for use in your makefiles.

sizesize (sizesize.U):
	This variable contains the size of a sizetype in bytes.

sizetype (sizetype.U):
	This variable defines sizetype to be something like size_t,
	unsigned long, or whatever type is used to declare length
	parameters for string functions.

sleep (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

sLOCALTIME_max (time_size.U):
	This variable defines the maximum value of the time_t offset that
	the system function localtime () accepts

sLOCALTIME_min (time_size.U):
	This variable defines the minimum value of the time_t offset that
	the system function localtime () accepts

smail (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

so (so.U):
	This variable holds the extension used to identify shared libraries
	(also known as shared objects) on the system. Usually set to 'so'.

sockethdr (d_socket.U):
	This variable has any cpp '-I' flags needed for socket support.

socketlib (d_socket.U):
	This variable has the names of any libraries needed for socket support.

socksizetype (socksizetype.U):
	This variable holds the type used for the size argument
	for various socket calls like accept.  Usual values include
	socklen_t, size_t, and int.

sort (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the sort program.  After Configure runs,
	the value is reset to a plain "sort" and is not useful.

spackage (package.U):
	This variable contains the name of the package being constructed,
	with the first letter uppercased, i.e. suitable for starting
	sentences.

spitshell (spitshell.U):
	This variable contains the command necessary to spit out a runnable
	shell on this system.  It is either cat or a grep '-v' for # comments.

sPRId64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit decimal numbers (format 'd') for output.

sPRIeldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'e') for output.

sPRIEUldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'E') for output.
	The 'U' in the name is to separate this from sPRIeldbl so that even
	case-blind systems can see the difference.

sPRIfldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'f') for output.

sPRIFUldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'F') for output.
	The 'U' in the name is to separate this from sPRIfldbl so that even
	case-blind systems can see the difference.

sPRIgldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'g') for output.

sPRIGUldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'G') for output.
	The 'U' in the name is to separate this from sPRIgldbl so that even
	case-blind systems can see the difference.

sPRIi64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit decimal numbers (format 'i') for output.

sPRIo64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit octal numbers (format 'o') for output.

sPRIu64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit unsigned decimal numbers (format 'u') for output.

sPRIx64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit hexadecimal numbers (format 'x') for output.

sPRIXU64 (quadfio.U):
	This variable, if defined, contains the string used by stdio to
	format 64-bit hExADECimAl numbers (format 'X') for output.
	The 'U' in the name is to separate this from sPRIx64 so that even
	case-blind systems can see the difference.

srand48_r_proto (d_srand48_r.U):
	This variable encodes the prototype of srand48_r.
	It is zero if d_srand48_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_srand48_r
	is defined.

srandom_r_proto (d_srandom_r.U):
	This variable encodes the prototype of srandom_r.
	It is zero if d_srandom_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_srandom_r
	is defined.

src (src.U):
	This variable holds the (possibly relative) path of the package source.
	It is up to the Makefile to use this variable and set VPATH accordingly
	to find the sources remotely.  Use $pkgsrc to have an absolute path.

sSCNfldbl (longdblfio.U):
	This variable, if defined, contains the string used by stdio to
	format long doubles (format 'f') for input.

ssizetype (ssizetype.U):
	This variable defines ssizetype to be something like ssize_t,
	long or int.  It is used by functions that return a count
	of bytes or an error condition.  It must be a signed type.
	We will pick a type such that sizeof(SSize_t) == sizeof(Size_t).

st_dev_sign (st_dev_def.U):
	This variable contains the signedness of struct stat's st_dev.
	1 for unsigned, -1 for signed.

st_dev_size (st_dev_def.U):
	This variable contains the size of struct stat's st_dev in bytes.

st_ino_sign (st_ino_def.U):
	This variable contains the signedness of struct stat's st_ino.
	1 for unsigned, -1 for signed.

st_ino_size (st_ino_def.U):
	This variable contains the size of struct stat's st_ino in bytes.

startperl (startperl.U):
	This variable contains the string to put on the front of a perl
	script to make sure (hopefully) that it runs with perl and not some
	shell. Of course, that leading line must be followed by the classical
	perl idiom:
	eval 'exec perl -S $0 ${1+"$@"}'
	if $running_under_some_shell;
	to guarantee perl startup should the shell execute the script. Note
	that this magic incantation is not understood by csh.

startsh (startsh.U):
	This variable contains the string to put on the front of a shell
	script to make sure (hopefully) that it runs with sh and not some
	other shell.

static_ext (Extensions.U):
	This variable holds a list of XS extension files we want to
	link statically into the package.  It is used by Makefile.

stdchar (stdchar.U):
	This variable conditionally defines STDCHAR to be the type of char
	used in stdio.h.  It has the values "unsigned char" or "char".

stdio_base (d_stdstdio.U):
	This variable defines how, given a FILE pointer, fp, to access the
	_base field (or equivalent) of stdio.h's FILE structure.  This will
	be used to define the macro FILE_base(fp).

stdio_bufsiz (d_stdstdio.U):
	This variable defines how, given a FILE pointer, fp, to determine
	the number of bytes store in the I/O buffer pointer to by the
	_base field (or equivalent) of stdio.h's FILE structure.  This will
	be used to define the macro FILE_bufsiz(fp).

stdio_cnt (d_stdstdio.U):
	This variable defines how, given a FILE pointer, fp, to access the
	_cnt field (or equivalent) of stdio.h's FILE structure.  This will
	be used to define the macro FILE_cnt(fp).

stdio_filbuf (d_stdstdio.U):
	This variable defines how, given a FILE pointer, fp, to tell
	stdio to refill its internal buffers (?).  This will
	be used to define the macro FILE_filbuf(fp).

stdio_ptr (d_stdstdio.U):
	This variable defines how, given a FILE pointer, fp, to access the
	_ptr field (or equivalent) of stdio.h's FILE structure.  This will
	be used to define the macro FILE_ptr(fp).

stdio_stream_array (stdio_streams.U):
	This variable tells the name of the array holding the stdio streams.
	Usual values include _iob, __iob, and __sF.

strerror_r_proto (d_strerror_r.U):
	This variable encodes the prototype of strerror_r.
	It is zero if d_strerror_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_strerror_r
	is defined.

submit (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

subversion (patchlevel.U):
	The subversion level of this package.
	The value of subversion comes from the patchlevel.h file.
	In a version number such as 5.6.1, this is the "1".
	In patchlevel.h, this is referred to as "PERL_SUBVERSION".
	This is unique to perl.

sysman (sysman.U):
	This variable holds the place where the manual is located on this
	system. It is not the place where the user wants to put his manual
	pages. Rather it is the place where Configure may look to find manual
	for unix commands (section 1 of the manual usually). See mansrc.

sysroot (Sysroot.U):
	This variable is empty unless supplied by the Configure user.
	It can contain a path to an alternative root directory, under which
	headers and libraries for the compilation target can be found. This
	is generally used when cross-compiling using a gcc-like compiler.

tail (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

tar (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

targetarch (Cross.U):
	If cross-compiling, this variable contains the target architecture.
	If not, this will be empty.

targetdir (Cross.U):
	This variable contains a path that will be created on the target
	host using targetmkdir, and then used to copy the cross-compiled
	executables to. Defaults to '/tmp' if not set.

targetenv (Cross.U):
	If cross-compiling, this variable can be used to modify the
	environment on the target system.
	However, how and where it's used, and even if it's used at all, is
	entirely dependent on both the transport mechanism (targetrun) and
	what the target system is.  Unless the relevant documentation says
	otherwise, it is genereally not useful.

targethost (Cross.U):
	This variable contains the name of a separate host machine that
	can be used to run compiled test programs and perl tests on.
	Set to empty string if not in use.

targetmkdir (Cross.U):
	This variable contains the command used by Configure to create a
	new directory on the target host.

targetport (Cross.U):
	This variable contains the number of a network port to be used to
	connect to the host in targethost, if unset defaults to 22 for ssh.

targetsh (sh.U):
	If cross-compiling, this variable contains the location of sh on the
	target system.
	If not, this will be the same as $sh.

tbl (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

tee (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

test (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the test program.  After Configure runs,
	the value is reset to a plain "test" and is not useful.

timeincl (i_time.U):
	This variable holds the full path of the included time header(s).

timetype (d_time.U):
	This variable holds the type returned by time(). It can be long,
	or time_t on BSD sites (in which case <sys/types.h> should be
	included). Anyway, the type Time_t should be used.

tmpnam_r_proto (d_tmpnam_r.U):
	This variable encodes the prototype of tmpnam_r.
	It is zero if d_tmpnam_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_tmpnam_r
	is defined.

to (Cross.U):
	This variable contains the command used by Configure
	to copy to from the target host.  Useful and available
	only during Perl build.
	The string ':' if not cross-compiling.

touch (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the touch program.  After Configure runs,
	the value is reset to a plain "touch" and is not useful.

tr (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the tr program.  After Configure runs,
	the value is reset to a plain "tr" and is not useful.

trnl (trnl.U):
	This variable contains the value to be passed to the tr(1)
	command to transliterate a newline.  Typical values are
	'\012' and '\n'.  This is needed for EBCDIC systems where
	newline is not necessarily '\012'.

troff (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

ttyname_r_proto (d_ttyname_r.U):
	This variable encodes the prototype of ttyname_r.
	It is zero if d_ttyname_r is undef, and one of the
	REENTRANT_PROTO_T_ABC macros of reentr.h if d_ttyname_r
	is defined.

u16size (perlxv.U):
	This variable is the size of an U16 in bytes.

u16type (perlxv.U):
	This variable contains the C type used for Perl's U16.

u32oformat (perlx32f.U):
	This variable contains the format string used for printing
	a Perl U32 as an unsigned octal integer.

u32size (perlxv.U):
	This variable is the size of an U32 in bytes.

u32type (perlxv.U):
	This variable contains the C type used for Perl's U32.

u32uformat (perlx32f.U):
	This variable contains the format string used for printing
	a Perl U32 as an unsigned decimal integer.

u32xformat (perlx32f.U):
	This variable contains the format string used for printing
	a Perl U32 as an unsigned hexadecimal integer in lowercase abcdef.

u32XUformat (perlx32f.U):
	This variable contains the format string used for printing
	a Perl U32 as an unsigned hexadecimal integer in uppercase ABCDEF.

u64size (perlxv.U):
	This variable is the size of an U64 in bytes.

u64type (perlxv.U):
	This variable contains the C type used for Perl's U64.

u8size (perlxv.U):
	This variable is the size of an U8 in bytes.

u8type (perlxv.U):
	This variable contains the C type used for Perl's U8.

uidformat (uidf.U):
	This variable contains the format string used for printing a Uid_t.

uidsign (uidsign.U):
	This variable contains the signedness of a uidtype.
	1 for unsigned, -1 for signed.

uidsize (uidsize.U):
	This variable contains the size of a uidtype in bytes.

uidtype (uidtype.U):
	This variable defines Uid_t to be something like uid_t, int,
	ushort, or whatever type is used to declare user ids in the kernel.

uname (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the uname program.  After Configure runs,
	the value is reset to a plain "uname" and is not useful.

uniq (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the uniq program.  After Configure runs,
	the value is reset to a plain "uniq" and is not useful.

uquadtype (quadtype.U):
	This variable defines Uquad_t to be something like unsigned long,
	unsigned int, unsigned long long, uint64_t, or whatever type is
	used for 64-bit integers.

use64bitall (use64bits.U):
	This variable conditionally defines the USE_64_BIT_ALL symbol,
	and indicates that 64-bit integer types should be used
	when available.  The maximal possible
	64-bitness is employed: LP64 or ILP64, meaning that you will
	be able to use more than 2 gigabytes of memory.  This mode is
	even more binary incompatible than USE_64_BIT_INT. You may not
	be able to run the resulting executable in a 32-bit CPU at all or
	you may need at least to reboot your OS to 64-bit mode.

use64bitint (use64bits.U):
	This variable conditionally defines the USE_64_BIT_INT symbol,
	and indicates that 64-bit integer types should be used
	when available.  The minimal possible 64-bitness
	is employed, just enough to get 64-bit integers into Perl.
	This may mean using for example "long longs", while your memory
	may still be limited to 2 gigabytes.

usecbacktrace (usebacktrace.U):
	This variable indicates whether we are compiling with backtrace
	support.

usecrosscompile (Cross.U):
	This variable conditionally defines the USE_CROSS_COMPILE symbol,
	and indicates that Perl has been cross-compiled.

usedefaultstrict (usedefaultstrict.U):
	This setting provides a mechanism for perl developers to enable
	strict by default. These defaults do not apply when perl is run
	via -e or -E.

usedevel (Devel.U):
	This variable indicates that Perl was configured with development
	features enabled.  This should not be done for production builds.

usedl (dlsrc.U):
	This variable indicates if the system supports dynamic
	loading of some sort.  See also dlsrc and dlobj.

usedtrace (usedtrace.U):
	This variable indicates whether we are compiling with dtrace
	support. See also dtrace.

usefaststdio (usefaststdio.U):
	This variable conditionally defines the USE_FAST_STDIO symbol,
	and indicates that Perl should be built to use 'fast stdio'.
	Defaults to define in Perls 5.8 and earlier, to undef later.

useithreads (usethreads.U):
	This variable conditionally defines the USE_ITHREADS symbol,
	and indicates that Perl should be built to use the interpreter-based
	threading implementation.

usekernprocpathname (usekernprocpathname.U):
	This variable, indicates that we can use sysctl with
	KERN_PROC_PATHNAME to get a full path for the executable, and hence
	convert $^X to an absolute path.

uselanginfo (Extensions.U):
	This variable holds either 'true' or 'false' to indicate
	whether the I18N::Langinfo extension should be used.  The sole
	use for this currently is to allow an easy mechanism for users to skip
	this extension from the Configure command line.

uselargefiles (uselfs.U):
	This variable conditionally defines the USE_LARGE_FILES symbol,
	and indicates that large file interfaces should be used when
	available.

uselongdouble (uselongdbl.U):
	This variable conditionally defines the USE_LONG_DOUBLE symbol,
	and indicates that long doubles should be used when available.

usemallocwrap (mallocsrc.U):
	This variable contains y if we are wrapping malloc to prevent
	integer overflow during size calculations.

usemorebits (usemorebits.U):
	This variable conditionally defines the USE_MORE_BITS symbol,
	and indicates that explicit 64-bit interfaces and long doubles
	should be used when available.

usemultiplicity (usemultiplicity.U):
	This variable conditionally defines the MULTIPLICITY symbol,
	and indicates that Perl should be built to use multiplicity.

usemymalloc (mallocsrc.U):
	This variable contains y if the malloc that comes with this package
	is desired over the system's version of malloc.  People often include
	special versions of malloc for efficiency, but such versions are often
	less portable.  See also mallocsrc and mallocobj.
	If this is 'y', then -lmalloc is removed from $libs.

usenm (usenm.U):
	This variable contains 'true' or 'false' depending whether the
	nm extraction is wanted or not.

usensgetexecutablepath (usensgetexecutablepath.U):
	This symbol, if defined, indicates that we can use _NSGetExecutablePath
	and realpath to get a full path for the executable, and hence convert
	$^X to an absolute path.

useopcode (Extensions.U):
	This variable holds either 'true' or 'false' to indicate
	whether the Opcode extension should be used.  The sole
	use for this currently is to allow an easy mechanism
	for users to skip the Opcode extension from the Configure
	command line.

useperlio (useperlio.U):
	This variable conditionally defines the USE_PERLIO symbol,
	and indicates that the PerlIO abstraction should be
	used throughout.

useposix (Extensions.U):
	This variable holds either 'true' or 'false' to indicate
	whether the POSIX extension should be used.  The sole
	use for this currently is to allow an easy mechanism
	for hints files to indicate that POSIX will not compile
	on a particular system.

usequadmath (usequadmath.U):
	This variable conditionally defines the USE_QUADMATH symbol,
	and indicates that the quadmath library __float128 long doubles
	should be used when available.

usereentrant (usethreads.U):
	This variable conditionally defines the USE_REENTRANT_API symbol,
	which indicates that the thread code may try to use the various
	_r versions of library functions.  This is only potentially
	meaningful if usethreads is set and is very experimental, it is
	not even prompted for.

userelocatableinc (bin.U):
	This variable is set to true to indicate that perl should relocate
	@INC entries at runtime based on the path to the perl binary.
	Any @INC paths starting ".../" are relocated relative to the directory
	containing the perl binary, and a logical cleanup of the path is then
	made around the join point (removing "dir/../" pairs)

useshrplib (libperl.U):
	This variable is set to 'true' if the user wishes
	to build a shared libperl, and 'false' otherwise.

usesitecustomize (d_sitecustomize.U):
	This variable is set to true when the user requires a mechanism that
	allows the sysadmin to add entries to @INC at runtime.  This variable
	being set, makes perl run '$sitelib/sitecustomize.pl' at startup.

usesocks (usesocks.U):
	This variable conditionally defines the USE_SOCKS symbol,
	and indicates that Perl should be built to use SOCKS.

usethreads (usethreads.U):
	This variable conditionally defines the USE_THREADS symbol,
	and indicates that Perl should be built to use threads.

usevendorprefix (vendorprefix.U):
	This variable tells whether the vendorprefix
	and consequently other vendor* paths are in use.

useversionedarchname (archname.U):
	This variable indicates whether to include the $api_versionstring
	as a component of the $archname.

usevfork (d_vfork.U):
	This variable is set to true when the user accepts to use vfork.
	It is set to false when no vfork is available or when the user
	explicitly requests not to use vfork.

usrinc (usrinc.U):
	This variable holds the path of the include files, which is
	usually /usr/include. It is mainly used by other Configure units.

uuname (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

uvoformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl UV as an unsigned octal integer.

uvsize (perlxv.U):
	This variable is the size of a UV in bytes.

uvtype (perlxv.U):
	This variable contains the C type used for Perl's UV.

uvuformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl UV as an unsigned decimal integer.

uvxformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl UV as an unsigned hexadecimal integer in lowercase abcdef.

uvXUformat (perlxvf.U):
	This variable contains the format string used for printing
	a Perl UV as an unsigned hexadecimal integer in uppercase ABCDEF.

vendorarch (vendorarch.U):
	This variable contains the value of the PERL_VENDORARCH symbol.
	It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	architecture-dependent modules and extensions in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorarchexp (vendorarch.U):
	This variable is the ~name expanded version of vendorarch, so that you
	may use it directly in Makefiles or shell scripts.

vendorbin (vendorbin.U):
	This variable contains the eventual value of the VENDORBIN symbol.
	It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place additional
	binaries in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorbinexp (vendorbin.U):
	This variable is the ~name expanded version of vendorbin, so that you
	may use it directly in Makefiles or shell scripts.

vendorhtml1dir (vendorhtml1dir.U):
	This variable contains the name of the directory for html
	pages.  It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	html pages in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorhtml1direxp (vendorhtml1dir.U):
	This variable is the ~name expanded version of vendorhtml1dir, so that you
	may use it directly in Makefiles or shell scripts.

vendorhtml3dir (vendorhtml3dir.U):
	This variable contains the name of the directory for html
	library pages.  It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	html pages for modules and extensions in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorhtml3direxp (vendorhtml3dir.U):
	This variable is the ~name expanded version of vendorhtml3dir, so that you
	may use it directly in Makefiles or shell scripts.

vendorlib (vendorlib.U):
	This variable contains the eventual value of the VENDORLIB symbol,
	which is the name of the private library for this package.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	modules in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorlib_stem (vendorlib.U):
	This variable is $vendorlibexp with any trailing version-specific component
	removed.  The elements in inc_version_list (inc_version_list.U) can
	be tacked onto this variable to generate a list of directories to search.

vendorlibexp (vendorlib.U):
	This variable is the ~name expanded version of vendorlib, so that you
	may use it directly in Makefiles or shell scripts.

vendorman1dir (vendorman1dir.U):
	This variable contains the name of the directory for man1
	pages.  It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	man1 pages in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorman1direxp (vendorman1dir.U):
	This variable is the ~name expanded version of vendorman1dir, so that you
	may use it directly in Makefiles or shell scripts.

vendorman3dir (vendorman3dir.U):
	This variable contains the name of the directory for man3
	pages.  It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place their own
	man3 pages in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorman3direxp (vendorman3dir.U):
	This variable is the ~name expanded version of vendorman3dir, so that you
	may use it directly in Makefiles or shell scripts.

vendorprefix (vendorprefix.U):
	This variable holds the full absolute path of the directory below
	which the vendor will install add-on packages.
	See INSTALL for usage and examples.

vendorprefixexp (vendorprefix.U):
	This variable holds the full absolute path of the directory below
	which the vendor will install add-on packages.  Derived from vendorprefix.

vendorscript (vendorscript.U):
	This variable contains the eventual value of the VENDORSCRIPT symbol.
	It may have a ~ on the front.
	The standard distribution will put nothing in this directory.
	Vendors who distribute perl may wish to place additional
	executable scripts in this directory with
	MakeMaker Makefile.PL INSTALLDIRS=vendor
	or equivalent.  See INSTALL for details.

vendorscriptexp (vendorscript.U):
	This variable is the ~name expanded version of vendorscript, so that you
	may use it directly in Makefiles or shell scripts.

version (patchlevel.U):
	The full version number of this package, such as 5.6.1 (or 5_6_1).
	This combines revision, patchlevel, and subversion to get the
	full version number, including any possible subversions.
	This is suitable for use as a directory name, and hence is
	filesystem dependent.

version_patchlevel_string (patchlevel.U):
	This is a string combining version, subversion and
	perl_patchlevel (if perl_patchlevel is non-zero).
	It is typically something like
	'version 7 subversion 1'  or
	'version 7 subversion 1 patchlevel 11224'
	It is computed here to avoid duplication of code in myconfig.SH
	and lib/Config.pm.

versiononly (versiononly.U):
	If set, this symbol indicates that only the version-specific
	components of a perl installation should be installed.
	This may be useful for making a test installation of a new
	version without disturbing the existing installation.
	Setting versiononly is equivalent to setting installperl's -v option.
	In particular, the non-versioned scripts and programs such as
	a2p, c2ph, h2xs, pod2*, and perldoc are not installed
	(see INSTALL for a more complete list).  Nor are the man
	pages installed.
	Usually, this is undef.

vi (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

xlibpth (libpth.U):
	This variable holds extra path (space-separated) used to find
	libraries on this platform, for example CPU-specific libraries
	(on multi-CPU platforms) may be listed here.

xlocale_needed (d_newlocale.U):
	This symbol, if defined, indicates that the C program should
	include <xlocale.h> to get newlocale() and its friends.

yacc (yacc.U):
	This variable holds the name of the compiler compiler we
	want to use in the Makefile. It can be yacc, byacc, or bison -y.

yaccflags (yacc.U):
	This variable contains any additional yacc flags desired by the
	user.  It is up to the Makefile to use this.

zcat (Loc.U):
	This variable is defined but not used by Configure.
	The value is the empty string and is not useful.

zip (Loc.U):
	This variable is used internally by Configure to determine the
	full pathname (if any) of the zip program.  After Configure runs,
	the value is reset to a plain "zip" and is not useful.