perl/pod/perl5300delta.pod

=encoding utf8

=head1 NAME

perl5300delta - what is new for perl v5.30.0

=head1 DESCRIPTION

This document describes differences between the 5.28.0 release and the 5.30.0
release.

If you are upgrading from an earlier release such as 5.26.0, first read
L<perl5280delta>, which describes differences between 5.26.0 and 5.28.0.

=head1 Notice

sv_utf8_(downgrade|decode) are no longer marked as experimental.
L<[GH #16822]|https://github.com/Perl/perl5/issues/16822>.

=head1 Core Enhancements

=head2 Limited variable length lookbehind in regular expression pattern matching is now experimentally supported

Using a lookbehind assertion (like C<(?<=foo?)> or C<(?<!ba{1,9}r)> previously
would generate an error and refuse to compile.  Now it compiles (if the
maximum lookbehind is at most 255 characters), but raises a warning in
the new C<experimental::vlb> warnings category.  This is to caution you
that the precise behavior is subject to change based on feedback from
use in the field.

See L<perlre/(?<=pattern)> and L<perlre/(?<!pattern)>.

=head2 The upper limit C<"n"> specifiable in a regular expression quantifier of the form C<"{m,n}"> has been doubled to 65534

The meaning of an unbounded upper quantifier C<"{m,}"> remains unchanged.
It matches 2**31 - 1 times on most platforms, and more on ones where a C
language short variable is more than 4 bytes long.

=head2 Unicode 12.1 is supported

Because of a change in Unicode release cycles, Perl jumps from Unicode
10.0 in Perl 5.28 to Unicode 12.1 in Perl 5.30.

For details on the Unicode changes, see
L<https://www.unicode.org/versions/Unicode11.0.0/> for 11.0;
L<https://www.unicode.org/versions/Unicode12.0.0/> for 12.0;
and
L<https://www.unicode.org/versions/Unicode12.1.0/> for 12.1.
(Unicode 12.1 differs from 12.0 only in the addition of a single
character, that for the new Japanese era name.)

The Word_Break property, as in past Perl releases, remains tailored to
behave more in line with expectations of Perl users.  This means that
sequential runs of horizontal white space characters are not broken
apart, but kept as a single run.  Unicode 11 changed from past versions
to be more in line with Perl, but it left several white space characters
as causing breaks: TAB, NO BREAK SPACE, and FIGURE SPACE (U+2007).  We
have decided to continue to use the previous Perl tailoring with regards
to these.

=head2 Wildcards in Unicode property value specifications are now partially supported

You can now do something like this in a regular expression pattern

 qr! \p{nv= /(?x) \A [0-5] \z / }!

which matches all Unicode code points whose numeric value is
between 0 and 5 inclusive.  So, it could match the Thai or Bengali
digits whose numeric values are 0, 1, 2, 3, 4, or 5.

This marks another step in implementing the regular expression features
the Unicode Consortium suggests.

Most properties are supported, with the remainder planned for 5.32.
Details are in L<perlunicode/Wildcards in Property Values>.

=head2 qr'\N{name}' is now supported

Previously it was an error to evaluate a named character C<\N{...}>
within a single quoted regular expression pattern (whose evaluation is
deferred from the normal place).  This restriction is now removed.

=head2 Turkic UTF-8 locales are now seamlessly supported

Turkic languages have different casing rules than other languages for
the characters C<"i"> and C<"I">.  The uppercase of C<"i"> is LATIN
CAPITAL LETTER I WITH DOT ABOVE (U+0130); and the lowercase of C<"I"> is LATIN
SMALL LETTER DOTLESS I (U+0131).  Unicode furnishes alternate casing
rules for use with Turkic languages.  Previously, Perl ignored these,
but now, it uses them when it detects that it is operating under a
Turkic UTF-8 locale.

=head2 It is now possible to compile perl to always use thread-safe locale operations

Previously, these calls were only used when the perl was compiled to be
multi-threaded.  To always enable them, add

 -Accflags='-DUSE_THREAD_SAFE_LOCALE'

to your F<Configure> flags.

=head2 Eliminate opASSIGN macro usage from core

This macro is still defined but no longer used in core

=head2 C<-Drv> now means something on C<-DDEBUGGING> builds

Now, adding the verbose flag (C<-Dv>) to the C<-Dr> flag turns on all
possible regular expression debugging.

=head1 Incompatible Changes

=head2 Assigning non-zero to C<$[> is fatal

Setting L<< C<$[>|perlvar/$[ >> to a non-zero value has been deprecated since
Perl 5.12 and now throws a fatal error.
See L<<< perldeprecation/Assigning non-zero to C<< $[ >> is fatal >>>.

=head2 Delimiters must now be graphemes

See L<perldeprecation/Use of unassigned code point or non-standalone grapheme
for a delimiter.>

=head2 Some formerly deprecated uses of an unescaped left brace C<"{"> in
regular expression patterns are now illegal

But to avoid breaking code unnecessarily, most instances that issued a
deprecation warning, remain legal and now have a non-deprecation warning
raised.  See L<perldeprecation/Unescaped left braces in regular expressions>.

=head2 Previously deprecated sysread()/syswrite() on :utf8 handles is now fatal

Calling sysread(), syswrite(), send() or recv() on a C<:utf8> handle,
whether applied explicitly or implicitly, is now fatal.  This was
deprecated in perl 5.24.

There were two problems with calling these functions on C<:utf8>
handles:

=over

=item *

All four functions only paid attention to the C<:utf8> flag.  Other
layers were completely ignored, so a handle with
C<:encoding(UTF-16LE)> layer would be treated as UTF-8.  Other layers,
such as compression are completely ignored with or without the
C<:utf8> flag.

=item *

sysread() and recv() would read from the handle, skipping any
validation by the layers, and do no validation of their own.  This
could lead to invalidly encoded perl scalars.

=back

L<[GH #14839]|https://github.com/Perl/perl5/issues/14839>.

=head2 my() in false conditional prohibited

Declarations such as C<my $x if 0> are no longer permitted.

L<[GH #16702]|https://github.com/Perl/perl5/issues/16702>.

=head2 Fatalize $* and $#

These special variables, long deprecated, now throw exceptions when used.

L<[GH #16718]|https://github.com/Perl/perl5/issues/16718>.

=head2 Fatalize unqualified use of dump()

The C<dump()> function, long discouraged, may no longer be used unless it is
fully qualified, I<i.e.>, C<CORE::dump()>.

L<[GH #16719]|https://github.com/Perl/perl5/issues/16719>.

=head2 Remove File::Glob::glob()

The C<File::Glob::glob()> function, long deprecated, has been removed and now
throws an exception which advises use of C<File::Glob::bsd_glob()> instead.

L<[GH #16721]|https://github.com/Perl/perl5/issues/16721>.

=head2 C<pack()> no longer can return malformed UTF-8

It croaks if it would otherwise return a UTF-8 string that contains
malformed UTF-8.  This protects against potential security threats.  This
is considered a bug fix as well.
L<[GH #16035]|https://github.com/Perl/perl5/issues/16035>.

=head2 Any set of digits in the Common script are legal in a script run of another script

There are several sets of digits in the Common script.  C<[0-9]> is the
most familiar.  But there are also C<[\x{FF10}-\x{FF19}]> (FULLWIDTH
DIGIT ZERO - FULLWIDTH DIGIT NINE), and several sets for use in
mathematical notation, such as the MATHEMATICAL DOUBLE-STRUCK DIGITs.
Any of these sets should be able to appear in script runs of, say,
Greek.  But the design of 5.30 overlooked all but the ASCII digits
C<[0-9]>, so the design was flawed.  This has been fixed, so is both a
bug fix and an incompatibility.
L<[GH #16704]|https://github.com/Perl/perl5/issues/16704>.

All digits in a run still have to come from the same set of ten digits.

=head2 JSON::PP enables allow_nonref by default

As JSON::XS 4.0 changed its policy and enabled allow_nonref
by default, JSON::PP also enabled allow_nonref by default.

=head1 Deprecations

=head2 In XS code, use of various macros dealing with UTF-8

This deprecation was scheduled to become fatal in 5.30, but has been
delayed to 5.32 due to problems that showed up with some CPAN modules.
For details of what's affected, see L<perldeprecation|
perldeprecation/In XS code, use of various macros dealing with UTF-8.>.

=head1 Performance Enhancements

=over 4

=item *

Translating from UTF-8 into the code point it represents now is done via a
deterministic finite automaton, speeding it up.  As a typical example,
C<ord("\x7fff")> now requires 12% fewer instructions than before.  The
performance of checking that a sequence of bytes is valid UTF-8 is similarly
improved, again by using a DFA.

=item *

Eliminate recursion from finalize_op().
L<[GH #11866]|https://github.com/Perl/perl5/issues/11866>.

=item *

A handful of small optimizations related to character folding
and character classes in regular expressions.

=item *

Optimization of C<IV> to C<UV> conversions.
L<[GH #16761]|https://github.com/Perl/perl5/issues/16761>.

=item *

Speed up of the integer stringification algorithm by processing
two digits at a time instead of one.
L<[GH #16769]|https://github.com/Perl/perl5/issues/16769>.

=item *

Improvements based on LGTM analysis and recommendation.
(L<https://lgtm.com/projects/g/Perl/perl5/alerts/?mode=tree>). 
L<[GH #16765]|https://github.com/Perl/perl5/issues/16765>.
L<[GH #16773]|https://github.com/Perl/perl5/issues/16773>.

=item *

Code optimizations in F<regcomp.c>, F<regcomp.h>, F<regexec.c>.

=item *

Regular expression pattern matching of things like C<qr/[^I<a>]/> is
significantly sped up, where I<a> is any ASCII character.  Other classes
can get this speed up, but which ones is complicated and depends on the
underlying bit patterns of those characters, so differs between ASCII
and EBCDIC platforms, but all case pairs, like C<qr/[Gg]/> are included,
as is C<[^01]>.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Archive::Tar> has been upgraded from version 2.30 to 2.32.

=item *

L<B> has been upgraded from version 1.74 to 1.76.

=item *

L<B::Concise> has been upgraded from version 1.003 to 1.004.

=item *

L<B::Deparse> has been upgraded from version 1.48 to 1.49.

=item *

L<bignum> has been upgraded from version 0.49 to 0.51.

=item *

L<bytes> has been upgraded from version 1.06 to 1.07.

=item *

L<Carp> has been upgraded from version 1.38 to 1.50

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.074 to 2.084.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.076 to 2.084.

=item *

L<Config::Extensions> has been upgraded from version 0.02 to 0.03.

=item *

L<Config::Perl::V>. has been upgraded from version 0.29 to 0.32. This was due
to a new configuration variable that has influence on binary compatibility:
C<USE_THREAD_SAFE_LOCALE>.

=item *

L<CPAN> has been upgraded from version 2.20 to 2.22.

=item *

L<Data::Dumper> has been upgraded from version 2.170 to 2.174

L<Data::Dumper> now avoids leaking when C<croak>ing.

=item *

L<DB_File> has been upgraded from version 1.840 to 1.843.

=item *

L<deprecate> has been upgraded from version 0.03 to 0.04.

=item *

L<Devel::Peek> has been upgraded from version 1.27 to 1.28.

=item *

L<Devel::PPPort> has been upgraded from version 3.40 to 3.52.

=item *

L<Digest::SHA> has been upgraded from version 6.01 to 6.02.

=item *

L<Encode> has been upgraded from version 2.97 to 3.01.

=item *

L<Errno> has been upgraded from version 1.29 to 1.30.

=item *

L<experimental> has been upgraded from version 0.019 to 0.020.

=item *

L<ExtUtils::CBuilder> has been upgraded from version 0.280230 to 0.280231.

=item *

L<ExtUtils::Manifest> has been upgraded from version 1.70 to 1.72.

=item *

L<ExtUtils::Miniperl> has been upgraded from version 1.08 to 1.09.

=item *

L<ExtUtils::ParseXS> has been upgraded from version 3.39 to 3.40.
C<OUTLIST> parameters are no longer incorrectly included in the
automatically generated function prototype.
L<[GH #16746]|https://github.com/Perl/perl5/issues/16746>.

=item *

L<feature> has been upgraded from version 1.52 to 1.54.

=item *

L<File::Copy> has been upgraded from version 2.33 to 2.34.

=item *

L<File::Find> has been upgraded from version 1.34 to 1.36.

C<$File::Find::dont_use_nlink> now defaults to 1 on all
platforms.
L<[GH #16759]|https://github.com/Perl/perl5/issues/16759>.

Variables C<< $Is_Win32 >> and C<< $Is_VMS >> are being initialized.

=item *

L<File::Glob> has been upgraded from version 1.31 to 1.32.

=item *

L<File::Path> has been upgraded from version 2.15 to 2.16.

=item *

L<File::Spec> has been upgraded from version 3.74 to 3.78.

Silence L<Cwd> warning on Android builds if C<targetsh> is not defined.

=item *

L<File::Temp> has been upgraded from version 0.2304 to 0.2309.

=item *

L<Filter::Util::Call> has been upgraded from version 1.58 to 1.59.

=item *

L<GDBM_File> has been upgraded from version 1.17 to 1.18.

=item *

L<HTTP::Tiny> has been upgraded from version 0.070 to 0.076.

=item *

L<I18N::Langinfo> has been upgraded from version 0.17 to 0.18.

=item *

L<IO> has been upgraded from version 1.39 to 1.40.

=item *

IO-Compress has been upgraded from version 2.074 to 2.084.

Adds support for C<< IO::Uncompress::Zstd >> and
C<< IO::Uncompress::UnLzip >>.

The C<< BinModeIn >> and C<< BinModeOut >> options are now no-ops.
ALL files will be read/written in binmode.

=item *

L<IPC::Cmd> has been upgraded from version 1.00 to 1.02.

=item *

L<JSON::PP> has been upgraded from version 2.97001 to 4.02.

L<JSON::PP> as JSON::XS 4.0 enables C<allow_nonref> by default.

=item *

L<lib> has been upgraded from version 0.64 to 0.65.

=item *

L<Locale::Codes> has been upgraded from version 3.56 to 3.57.

=item *

L<Math::BigInt> has been upgraded from version 1.999811 to 1.999816.

C<< bnok() >> now supports the full Kronenburg extension.
L<[cpan #95628]|https://rt.cpan.org/Ticket/Display.html?id=95628>.

=item *

L<Math::BigInt::FastCalc> has been upgraded from version 0.5006 to 0.5008.

=item *

L<Math::BigRat> has been upgraded from version 0.2613 to 0.2614.

=item *

L<Module::CoreList> has been upgraded from version 5.20180622 to 5.20190520.

Changes to B::Op_private and Config

=item *

L<Module::Load> has been upgraded from version 0.32 to 0.34.

=item *

L<Module::Metadata> has been upgraded from version 1.000033 to 1.000036.

Properly clean up temporary directories after testing.

=item *

L<NDBM_File> has been upgraded from version 1.14 to 1.15.

=item *

L<Net::Ping> has been upgraded from version 2.62 to 2.71.

=item *

L<ODBM_File> has been upgraded from version 1.15 to 1.16.

=item *

PathTools has been upgraded from version 3.74 to 3.78.

=item *

L<parent> has been upgraded from version 0.236 to 0.237.

=item *

L<perl5db.pl> has been upgraded from version 1.54 to 1.55.

Debugging threaded code no longer deadlocks in C<DB::sub> nor
C<DB::lsub>.

=item *

L<perlfaq> has been upgraded from version 5.021011 to 5.20190126.

=item *

L<PerlIO::encoding> has been upgraded from version 0.26 to 0.27.

Warnings enabled by setting the C<WARN_ON_ERR> flag in
C<$PerlIO::encoding::fallback> are now only produced if warnings are
enabled with C<use warnings "utf8";> or setting C<$^W>.

=item *

L<PerlIO::scalar> has been upgraded from version 0.29 to 0.30.

=item *

podlators has been upgraded from version 4.10 to 4.11.

=item *

L<POSIX> has been upgraded from version 1.84 to 1.88.

=item *

L<re> has been upgraded from version 0.36 to 0.37.

=item *

L<SDBM_File> has been upgraded from version 1.14 to 1.15.

=item *

L<sigtrap> has been upgraded from version 1.08 to 1.09.

=item *

L<Storable> has been upgraded from version 3.08 to 3.15.

Storable no longer probes for recursion limits at build time.
L<[GH #16780]|https://github.com/Perl/perl5/issues/16780>
and others.

Metasploit exploit code was included to test for CVE-2015-1592
detection, this caused anti-virus detections on at least one AV suite.
The exploit code has been removed and replaced with a simple
functional test.
L<[GH #16778]|https://github.com/Perl/perl5/issues/16778>

=item *

L<Test::Simple> has been upgraded from version 1.302133 to 1.302162.

=item *

L<Thread::Queue> has been upgraded from version 3.12 to 3.13.

=item *

L<threads::shared> has been upgraded from version 1.58 to 1.60.

Added support for extra tracing of locking, this requires a
C<-DDEBUGGING> and extra compilation flags.

=item *

L<Time::HiRes> has been upgraded from version 1.9759 to 1.9760.

=item *

L<Time::Local> has been upgraded from version 1.25 to 1.28.

=item *

L<Time::Piece> has been upgraded from version 1.3204 to 1.33.

=item *

L<Unicode::Collate> has been upgraded from version 1.25 to 1.27.

=item *

L<Unicode::UCD> has been upgraded from version 0.70 to 0.72.

=item *

L<User::grent> has been upgraded from version 1.02 to 1.03.

=item *

L<utf8> has been upgraded from version 1.21 to 1.22.

=item *

L<vars> has been upgraded from version 1.04 to 1.05.

C<vars.pm> no longer disables non-vars strict when checking if strict
vars is enabled.
L<[GH #15851]|https://github.com/Perl/perl5/issues/15851>.

=item *

L<version> has been upgraded from version 0.9923 to 0.9924.

=item *

L<warnings> has been upgraded from version 1.42 to 1.44.

=item *

L<XS::APItest> has been upgraded from version 0.98 to 1.00.

=item *

L<XS::Typemap> has been upgraded from version 0.16 to 0.17.

=back

=head2 Removed Modules and Pragmata

The following modules will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
Distributions on CPAN which require these modules will need to list them as
prerequisites.

The core versions of these modules will now issue C<"deprecated">-category
warnings to alert you to this fact.  To silence these deprecation warnings,
install the modules in question from CPAN.

Note that these are (with rare exceptions) fine modules that you are encouraged
to continue to use.  Their disinclusion from core primarily hinges on their
necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
not usually on concerns over their design.

=over 4

=item *

arybase has been removed. It used to provide the implementation of the C<$[>
variable (also known as the C<array_base> feature), letting array and string
indices start at a non-zero value. As the feature has been removed (see
L</Assigning non-zero to C<$[> is fatal>), this internal module is gone as
well.

=item *

B::Debug is no longer distributed with the core distribution.  It
continues to be available on CPAN as
C<< L<B::Debug|https://metacpan.org/pod/B::Debug> >>.

=item *

Locale::Codes has been removed at the request of its author.  It
continues to be available on CPAN as
C<< L<Locale::Codes|https://metacpan.org/pod/Locale::Codes> >>
L<[GH #16660]|https://github.com/Perl/perl5/issues/16660>.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes
listed in this document.  If you find any we have missed, send email
to L<perlbug@perl.org|mailto:perlbug@perl.org>.

=head3 L<perlapi>

=over 4

=item *

C<AvFILL()> was wrongly listed as deprecated.  This has been corrected.
L<[GH #16586]|https://github.com/Perl/perl5/issues/16586>

=back

=head3 L<perlop>

=over 4

=item *

We no longer have null (empty line) here doc terminators, so
L<perlop> should not refer to them.

=item *

The behaviour of C<tr> when the delimiter is an apostrophe has been clarified.
In particular, hyphens aren't special, and C<\x{}> isn't interpolated.
L<[GH #15853]|https://github.com/Perl/perl5/issues/15853>

=back

=head3 L<perlreapi>, L<perlvar>

=over 4

=item *

Improve docs for lastparen, lastcloseparen.

=back

=head3 L<perlfunc>

=over 4

=item *

The entry for L<perlfunc/-X> has been clarified to indicate that symbolic
links are followed for most tests.

=item *

Clarification of behaviour of C<reset EXPR>.

=item *

Try to clarify that C<< ref(qr/xx/) >> returns C<Regexp> rather than
C<REGEXP> and why.
L<[GH #16801]|https://github.com/Perl/perl5/issues/16801>.

=back

=head3 L<perlreref>

=over 4

=item *

Clarification of the syntax of /(?(cond)yes)/.

=back

=head3 L<perllocale>

=over 4

=item *

There are actually two slightly different types of UTF-8 locales: one for Turkic
languages and one for everything else. Starting in Perl v5.30, Perl seamlessly 
handles both types.

=back

=head3 L<perlrecharclass>

=over 4

=item *

Added a note for the ::xdigit:: character class.

=back

=head3 L<perlvar>

=over 4

=item *

More specific documentation of paragraph mode.
L<[GH #16787]|https://github.com/Perl/perl5/issues/16787>.

=back

=head1 Diagnostics

The following additions or changes have been made to diagnostic output,
including warnings and fatal error messages.  For the complete list of
diagnostic messages, see L<perldiag>.

=head2 Changes to Existing Diagnostics

=over 4

=item *

As noted under L<Incompatible Changes> above, the deprecation warning
"Unescaped left brace in regex is deprecated here (and will be fatal in Perl
5.30), passed through in regex; marked by S<<-- HERE> in m/%s/" has been
changed to the non-deprecation warning "Unescaped left brace in regex is passed
through in regex; marked by S<<-- HERE> in m/%s/".

=item *

Specifying C<\o{}> without anything between the braces now yields the
fatal error message "Empty \o{}".  Previously it was  "Number with no
digits".  This means the same wording is used for this kind of error as
with similar constructs such as C<\p{}>.

=item *

Within the scope of the experimental feature C<use re 'strict'>,
specifying C<\x{}> without anything between the braces now yields the
fatal error message "Empty \x{}".  Previously it was  "Number with no
digits".  This means the same wording is used for this kind of error as
with similar constructs such as C<\p{}>.  It is legal, though not wise
to have an empty C<\x> outside of C<re 'strict'>; it silently generates
a NUL character.

=item *

L<Type of arg %d to %s must be %s (not %s)|perldiag/"Type of arg %d to %s must be %s (not %s)">

Attempts to push, pop, etc on a hash or glob now produce this message
rather than complaining that they no longer work on scalars.
L<[GH #15774]|https://github.com/Perl/perl5/issues/15774>.

=item *

L<Prototype not terminated|perldiag/"Prototype not terminated">

The file and line number is now reported for this error.
L<[GH #16697]|https://github.com/Perl/perl5/issues/16697>

=item *

Under C<< -Dr >> (or C<< use re 'Debug' >>) the compiled regex engine
program is displayed. It used to use two different spellings for I<<
infinity >>,
C<< INFINITY >>, and C<< INFTY >>. It now uses the latter exclusively,
as that spelling has been around the longest.

=back

=head1 Utility Changes

=head2 L<xsubpp>

=over 4

=item *

The generated prototype (with C<< PROTOTYPES: ENABLE >>) would include
C<< OUTLIST >> parameters, but these aren't arguments to the perl function.
This has been rectified.
L<[GH #16746]|https://github.com/Perl/perl5/issues/16746>.

=back

=head1 Configuration and Compilation

=over 4

=item *

Normally the thread-safe locale functions are used only on threaded
builds.  It is now possible to force their use on unthreaded builds on
systems that have them available, by including the
C<-Accflags='-DUSE_THREAD_SAFE_LOCALE'> option to F<Configure>.

=item *

Improve detection of memrchr, strlcat, and strlcpy

=item *

Improve Configure detection of memmem().
L<[GH #16807]|https://github.com/Perl/perl5/issues/16807>.

=item *

Multiple improvements and fixes for -DPERL_GLOBAL_STRUCT build option.

=item *

Fix -DPERL_GLOBAL_STRUCT_PRIVATE build option.

=back

=head1 Testing

=over 4

=item *

F<t/lib/croak/op>
L<[GH #15774]|https://github.com/Perl/perl5/issues/15774>.

separate error for C<push>, etc. on hash/glob.

=item *

F<t/op/svleak.t>
L<[GH #16749]|https://github.com/Perl/perl5/issues/16749>.

Add test for C<goto &sub> in overload leaking.

=item *

Split F<t/re/fold_grind.t> into multiple test files.

=item *

Fix intermittent tests which failed due to race conditions which
surface during parallel testing.
L<[GH #16795]|https://github.com/Perl/perl5/issues/16795>.

=item *

Thoroughly test paragraph mode, using a new test file,
F<t/io/paragraph_mode.t>.
L<[GH #16787]|https://github.com/Perl/perl5/issues/16787>.

=item *

Some tests in F<< t/io/eintr.t >> caused the process to hang on
pre-16 Darwin. These tests are skipped for those version of Darwin.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item HP-UX 11.11

An obscure problem in C<pack()> when compiling with HP C-ANSI-C has been fixed
by disabling optimizations in F<pp_pack.c>.

=item Mac OS X

Perl's build and testing process on Mac OS X for C<-Duseshrplib>
builds is now compatible with Mac OS X System Integrity Protection
(SIP).

SIP prevents binaries in F</bin> (and a few other places) being passed
the C<DYLD_LIBRARY_PATH> environment variable.  For our purposes this
prevents C<DYLD_LIBRARY_PATH> from being passed to the shell, which
prevents that variable being passed to the testing or build process,
so running C<perl> couldn't find F<libperl.dylib>.

To work around that, the initial build of the F<perl> executable
expects to find F<libperl.dylib> in the build directory, and the
library path is then adjusted during installation to point to the
installed library.

L<[GH #15057]|https://github.com/Perl/perl5/issues/15057>.

=item Minix3

Some support for Minix3 has been re-added.

=item Cygwin

Cygwin doesn't make C<< cuserid >> visible.

=item Win32 Mingw

C99 math functions are now available.

=item Windows

=over 4

=item *

The C<USE_CPLUSPLUS> build option which has long been available in
F<win32/Makefile> (for B<nmake>) and F<win32/makefile.mk> (for B<dmake>) is now
also available in F<win32/GNUmakefile> (for B<gmake>).

=item *

The B<nmake> makefile no longer defaults to Visual C++ 6.0 (a very old version
which is unlikely to be widely used today).  As a result, it is now a
requirement to specify the C<CCTYPE> since there is no obvious choice of which
modern version to default to instead.  Failure to specify C<CCTYPE> will result
in an error being output and the build will stop.

(The B<dmake> and B<gmake> makefiles will automatically detect which compiler
is being used, so do not require C<CCTYPE> to be set.  This feature has not yet
been added to the B<nmake> makefile.)

=item *

C<sleep()> with warnings enabled for a C<USE_IMP_SYS> build no longer
warns about the sleep timeout being too large.
L<[GH #16631]|https://github.com/Perl/perl5/issues/16631>.

=item *

Support for compiling perl on Windows using Microsoft Visual Studio 2019
(containing Visual C++ 14.2) has been added.

=item *

socket() now sets C<$!> if the protocol, address family and socket
type combination is not found.
L<[GH #16849]|https://github.com/Perl/perl5/issues/16849>.

=item *

The Windows Server 2003 SP1 Platform SDK build, with its early x64 compiler and
tools, was accidentally broken in Perl 5.27.9.  This has now been fixed.

=back

=back

=head1 Internal Changes

=over 4

=item *

The sizing pass has been eliminated from the regular expression
compiler.  An extra pass may instead be needed in some cases to count
the number of parenthetical capture groups.

=item *

A new function L<perlapi/C<my_strtod>> or its synonym, Strtod(), is
now available with the same signature as the libc strtod().  It provides
strotod() equivalent behavior on all platforms, using the best available
precision, depending on platform capabilities and F<Configure> options,
while handling locale-related issues, such as if the radix character
should be a dot or comma.

=item *

Added C<newSVsv_nomg()> to copy a SV without processing get magic on
the source.
L<[GH #16461]|https://github.com/Perl/perl5/issues/16461>.

=item *

It is now forbidden to malloc more than C<PTRDIFF_T_MAX> bytes.  Much
code (including C optimizers) assumes that all data structures will not
be larger than this, so this catches such attempts before overflow
happens.

=item *

Two new regnodes have been introduced C<< EXACT_ONLY8 >>, and
C<< EXACTFU_ONLY8 >>. They're equivalent to C<< EXACT >> and C<< EXACTFU >>,
except that they contain a code point which requires UTF-8 to
represent/match. Hence, if the target string isn't UTF-8, we know
it can't possibly match, without needing to try.

=item *

C<< print_bytes_for_locale() >> is now defined if C<< DEBUGGING >>,
Prior, it didn't get defined unless C<< LC_COLLATE >> was defined
on the platform.

=back

=head1 Selected Bug Fixes

=over 4

=item *

Compilation under C<-DPERL_MEM_LOG> and C<-DNO_LOCALE> have been fixed.

=item *

Perl 5.28 introduced an C<index()> optimization when comparing to -1 (or
indirectly, e.g. >= 0).  When this optimization was triggered inside a C<when>
clause it caused a warning ("Argument %s isn't numeric in smart match").  This
has now been fixed.
L<[GH #16626]|https://github.com/Perl/perl5/issues/16626>

=item *

The new in-place editing code no longer leaks directory handles.
L<[GH #16602]|https://github.com/Perl/perl5/issues/16602>.

=item *

Warnings produced from constant folding operations on overloaded
values no longer produce spurious "Use of uninitialized value"
warnings.
L<[GH #16349]|https://github.com/Perl/perl5/issues/16349>.

=item *

Fix for "mutator not seen in (lex = ...) .= ..."
L<[GH #16655]|https://github.com/Perl/perl5/issues/16655>.

=item *

C<pack "u", "invalid uuencoding"> now properly NUL terminates the
zero-length SV produced.
L<[GH #16343]|https://github.com/Perl/perl5/issues/16343>.

=item *

Improve the debugging output for calloc() calls with C<-Dm>.
L<[GH #16653]|https://github.com/Perl/perl5/issues/16653>.

=item *

Regexp script runs were failing to permit ASCII digits in some cases.
L<[GH #16704]|https://github.com/Perl/perl5/issues/16704>.

=item *

On Unix-like systems supporting a platform-specific technique for
determining L<< C<$^X>|perlvar/$^X >>, Perl failed to fall back to the
generic technique when the platform-specific one fails (for example, a Linux
system with /proc not mounted).  This was a regression in Perl 5.28.0.
L<[GH #16715]|https://github.com/Perl/perl5/issues/16715>.

=item *

L<SDBM_File> is now more robust with corrupt database files.  The
improvements do not make SDBM files suitable as an interchange format.
L<[GH #16164]|https://github.com/Perl/perl5/issues/16164>.

=item *

C<binmode($fh);> or C<binmode($fh, ':raw');> now properly removes the
C<:utf8> flag from the default C<:crlf> I/O layer on Win32.
L<[GH #16730]|https://github.com/Perl/perl5/issues/16730>.

=item *

The experimental reference aliasing feature was misinterpreting array and
hash slice assignment as being localised, e.g.

    \(@a[3,5,7]) = \(....);

was being interpreted as:

    local \(@a[3,5,7]) = \(....);

L<[GH #16701]|https://github.com/Perl/perl5/issues/16701>.

=item *

C<sort SUBNAME> within an C<eval EXPR> when C<EXPR> was UTF-8 upgraded
could panic if the C<SUBNAME> was non-ASCII.
L<[GH #16979]|https://github.com/Perl/perl5/issues/16979>.

=item *

Correctly handle realloc() modifying C<errno> on success so that the
modification isn't visible to the perl user, since realloc() is called
implicitly by the interpreter.  This modification is permitted by the
C standard, but has only been observed on FreeBSD 13.0-CURRENT.
L<[GH #16907]|https://github.com/Perl/perl5/issues/16907>.

=item *

Perl now exposes POSIX C<getcwd> as C<Internals::getcwd()> if
available.  This is intended for use by C<Cwd.pm> during bootstrapping
and may be removed or changed without notice.  This fixes some
bootstrapping issues while building perl in a directory where some
ancestor directory isn't readable.
L<[GH #16903]|https://github.com/Perl/perl5/issues/16903>.

=item *

C<pack()> no longer can return malformed UTF-8.  It croaks if it would
otherwise return a UTF-8 string that contains malformed UTF-8.  This
protects against potential security threats.
L<[GH #16035]|https://github.com/Perl/perl5/issues/16035>.

=item *

See L</Any set of digits in the Common script are legal in a script run
of another script>.

=item *

Regular expression matching no longer leaves stale UTF-8 length magic
when updating C<$^R>. This could result in C<length($^R)> returning
an incorrect value.

=item *

Reduce recursion on ops
L<[GH #11866]|https://github.com/Perl/perl5/issues/11866>.

This can prevent stack overflow when processing extremely deep op
trees.

=item *

Avoid leak in multiconcat with overloading.
L<[GH #16823]|https://github.com/Perl/perl5/issues/16823>.

=item *

The handling of user-defined C<\p{}> properties (see
L<perlunicode/User-Defined Character Properties>) has been rewritten to
be in C (instead of Perl).  This speeds things up, but in the process
several inconsistencies and bug fixes are made.

=over 4

=item 1

A few error messages have minor wording changes.  This is essentially
because the new way is integrated into the regex error handling
mechanism that marks the position in the input at which the error
occurred.  That was not possible previously.  The messages now also
contain additional back-trace-like information in case the error occurs
deep in nested calls.

=item 2

A user-defined property is implemented as a perl subroutine with certain
highly constrained naming conventions.  It was documented previously
that the sub would be in the current package if the package was
unspecified.  This turned out not to be true in all cases, but now it
is.

=item 3

All recursive calls are treated as infinite recursion.  Previously they
would cause the interpreter to panic.  Now, they cause the regex pattern
to fail to compile.

=item 4

Similarly, any other error likely would lead to a panic; now to just the
pattern failing to compile.

=item 5

The old mechanism did not detect illegal ranges in the definition of the
property.  Now, the range max must not be smaller than the range min.
Otherwise, the pattern fails to compile.

=item 6

The intention was to have each sub called only once during the lifetime
of the program, so that a property's definition is immutable.  This was
relaxed so that it could be called once for all /i compilations, and
potentially a second time for non-/i (the sub is passed a parameter
indicating which).  However, in practice there were instances when this
was broken, and multiple calls were possible.  Those have been fixed.
Now (besides the /i,non-/i cases) the only way a sub can be called
multiple times is if some component of it has not been defined yet.  For
example, suppose we have sub IsA() whose definition is known at compile
time, and it in turn calls isB() whose definition is not yet known.
isA() will be called each time a pattern it appears in is compiled.  If
isA() also calls isC() and that definition is known, isC() will be
called just once.

=item 7

There were some races and very long hangs should one thread be compiling
the same property as another simultaneously.  These have now been fixed.

=back

=item *

Fixed a failure to match properly.

An EXACTFish regnode has a finite length it can hold for the string
being matched.  If that length is exceeded, a second node is used for
the next segment of the string, for as many regnodes as are needed.
Care has to be taken where to break the string, in order to deal
multi-character folds in Unicode correctly. If we want to break a
string at a place which could potentially be in the middle of a
multi-character fold, we back off one (or more) characters, leaving
a shorter EXACTFish regnode. This backing off mechanism contained
an off-by-one error.
L<[GH #16806]|https://github.com/Perl/perl5/issues/16806>.

=item *

A bare C<eof> call with no previous file handle now returns true.
L<[GH #16786]|https://github.com/Perl/perl5/issues/16786>

=item *

Failing to compile a format now aborts compilation.  Like other errors
in sub-parses this could leave the parser in a strange state, possibly
crashing perl if compilation continued.
L<[GH #16169]|https://github.com/Perl/perl5/issues/16169>

=item *

If an in-place edit is still in progress during global destruction and
the process exit code (as stored in C<$?>) is zero, perl will now
treat the in-place edit as successful, replacing the input file with
any output produced.

This allows code like:

  perl -i -ne 'print "Foo"; last'

to replace the input file, while code like:

  perl -i -ne 'print "Foo"; die'

will not.  Partly resolves
L<[GH #16748]|https://github.com/Perl/perl5/issues/16748>.

=item *

A regression in 5.28 caused the following code to fail

 close(STDIN); open(CHILD, "|wc -l")'

because the child's stdin would be closed on exec. This has now been fixed.

=item *

Fixed an issue where compiling a regexp containing both compile-time
and run-time code blocks could lead to trying to compile something
which is invalid syntax.

=item *

Fixed build failures with C<< -DNO_LOCALE_NUMERIC >> and
C<< -DNO_LOCALE_COLLATE >>.
L<[GH #16771]|https://github.com/Perl/perl5/issues/16771>.

=item *

Prevent the tests in F<< ext/B/t/strict.t >> from being skipped.
L<[GH #16783]|https://github.com/Perl/perl5/issues/16783>.

=item *

C<< /di >> nodes ending or beginning in I<s> are now C<< EXACTF >>. We do not
want two C<< EXACTFU >> to be joined together during optimization,
and to form a C<< ss >>, C<< sS >>, C<< Ss >> or C<< SS >> sequence;
they are the only multi-character sequences which may match differently
under C<< /ui >> and C<< /di >>.

=back

=head1 Acknowledgements

Perl 5.30.0 represents approximately 11 months of development since Perl
5.28.0 and contains approximately 620,000 lines of changes across 1,300
files from 58 authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 510,000 lines of changes to 750 .pm, .t, .c and .h files.

Perl continues to flourish into its fourth decade thanks to a vibrant
community of users and developers. The following people are known to have
contributed the improvements that became Perl 5.30.0:

Aaron Crane, Abigail, Alberto Simões, Alexandr Savca, Andreas König, Andy
Dougherty, Aristotle Pagaltzis, Brian Greenfield, Chad Granum, Chris
'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan Book, Dan
Dedrick, Daniel Dragan, Dan Kogai, David Cantrell, David Mitchell, Dominic
Hargreaves, E. Choroba, Ed J, Eugen Konkov, François Perrad, Graham Knop,
Hauke D, H.Merijn Brand, Hugo van der Sanden, Jakub Wilk, James Clarke,
James E Keenan, Jerry D. Hedden, Jim Cromie, John SJ Anderson, Karen
Etheridge, Karl Williamson, Leon Timmermans, Matthias Bethke, Nicholas
Clark, Nicolas R., Niko Tyni, Pali, Petr Písař, Phil Pearl (Lobbes),
Richard Leach, Ryan Voots, Sawyer X, Shlomi Fish, Sisyphus, Slaven Rezic,
Steve Hay, Sullivan Beck, Tina Müller, Tomasz Konojacki, Tom Wyant, Tony
Cook, Unicode Consortium, Yves Orton, Zak B. Elep.

The list above is almost certainly incomplete as it is automatically
generated from version control history. In particular, it does not include
the names of most of the (very much appreciated) contributors who reported
issues to the Perl bug tracker. Noteworthy in this release were the large
number of bug fixes made possible by Sergey Aleynikov's high quality perlbug
reports for issues he discovered by fuzzing with AFL.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core. We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please
see the F<AUTHORS> file in the Perl source distribution.

=head1 Reporting Bugs

If you find what you think is a bug, you might check the perl bug database
at L<https://rt.perl.org/>.  There may also be information at
L<http://www.perl.org/>, the Perl Home Page.

If you believe you have an unreported bug, please run the L<perlbug> program
included with your release.  Be sure to trim your bug down to a tiny but
sufficient test case.  Your bug report, along with the output of C<perl -V>,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications which make it
inappropriate to send to a publicly archived mailing list, then see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

=head1 Give Thanks

If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
you can do so by running the C<perlthanks> program:

    perlthanks

This will send an email to the Perl 5 Porters list with your show of thanks.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details on
what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut