[DOC] Harmonize #=== methods

Merged: https://github.com/ruby/ruby/pull/15807

object.c

@@ -162,7 +162,7 @@ rb_obj_setup(VALUE obj, VALUE klass, VALUE type)
  *
  * Returns +true+ or +false+.
  *
- * Like Object#==, if +object+ is an instance of Object
+ * Like Object#==, if +other+ is an instance of \Object
  * (and not an instance of one of its many subclasses).
  *
  * This method is commonly overridden by those subclasses,
@@ -1892,11 +1892,12 @@ rb_mod_freeze(VALUE mod)
 
 /*
  *  call-seq:
- *     mod === obj    -> true or false
+ *     self === other -> true or false
  *
- *  Case Equality---Returns <code>true</code> if <i>obj</i> is an
- *  instance of <i>mod</i> or an instance of one of <i>mod</i>'s descendants.
- *  Of limited use for modules, but can be used in <code>case</code> statements
+ *  Returns whether +other+ is an instance of +self+,
+ *  or is an instance of a subclass of +self+.
+ *
+ *  Of limited use for modules, but can be used in +case+ statements
  *  to classify objects by class.
  */
 

range.c

@@ -2054,10 +2054,9 @@ VALUE rb_str_include_range_p(VALUE beg, VALUE end, VALUE val, VALUE exclusive);
 
 /*
  *  call-seq:
- *     self === object ->  true or false
+ *     self === other ->  true or false
  *
- *  Returns +true+ if +object+ is between <tt>self.begin</tt> and <tt>self.end</tt>.
- *  +false+ otherwise:
+ *  Returns whether +other+ is between <tt>self.begin</tt> and <tt>self.end</tt>:
  *
  *    (1..4) === 2       # => true
  *    (1..4) === 5       # => false

re.c

@@ -3728,9 +3728,9 @@ rb_reg_match(VALUE re, VALUE str)
 
 /*
  *  call-seq:
- *    regexp === string -> true or false
+ *    self === other -> true or false
  *
- *  Returns +true+ if +self+ finds a match in +string+:
+ *  Returns whether +self+ finds a match in +other+:
  *
  *    /^[a-z]*$/ === 'HELLO' # => false
  *    /^[A-Z]*$/ === 'HELLO' # => true