=head1 NAME
-perldelta - what is new for perl v5.22.0
+[ this is a template for a new perldelta file. Any text flagged as XXX needs
+to be processed before release. ]
+
+perldelta - what is new for perl v5.23.1
=head1 DESCRIPTION
-This document describes differences between the 5.20.0 release and the 5.22.0
+This document describes differences between the 5.23.0 release and the 5.23.1
release.
-If you are upgrading from an earlier release such as 5.18.0, first read
-L<perl5200delta>, which describes differences between 5.18.0 and 5.20.0.
-
-=head1 Core Enhancements
-
-=head2 New bitwise operators
-
-A new experimental facility has been added that makes the four standard
-bitwise operators (C<& | ^ ~>) treat their operands consistently as
-numbers, and introduces four new dotted operators (C<&. |. ^. ~.>) that
-treat their operands consistently as strings. The same applies to the
-assignment variants (C<&= |= ^= &.= |.= ^.=>).
-
-To use this, enable the "bitwise" feature and disable the
-"experimental::bitwise" warnings category. See L<perlop/Bitwise String
-Operators> for details.
-L<[perl #123466]|https://rt.perl.org/Ticket/Display.html?id=123466>.
-
-=head2 New double-diamond operator
-
-C<<< <<>> >>> is like C<< <> >> but uses three-argument C<open> to open
-each file in C<@ARGV>. This means that each element of C<@ARGV> will be treated
-as an actual file name, and C<"|foo"> won't be treated as a pipe open.
-
-=head2 New \b boundaries in regular expressions
-
-=head3 qr/\b{gcb}/
-
-C<gcb> stands for Grapheme Cluster Boundary. It is a Unicode property
-that finds the boundary between sequences of characters that look like a
-single character to a native speaker of a language. Perl has long had
-the ability to deal with these through the C<\X> regular escape
-sequence. Now, there is an alternative way of handling these. See
-L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
-
-=head3 qr/\b{wb}/
-
-C<wb> stands for Word Boundary. It is a Unicode property
-that finds the boundary between words. This is similar to the plain
-C<\b> (without braces) but is more suitable for natural language
-processing. It knows, for example, that apostrophes can occur in the
-middle of words. See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
-
-=head3 qr/\b{sb}/
-
-C<sb> stands for Sentence Boundary. It is a Unicode property
-to aid in parsing natural language sentences.
-See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
-
-=head2 C<no re> covers more and is lexical
-
-Previously running C<no re> would only turn off a few things. Now it
-turns off all the enabled things. For example, previously, you
-couldn't turn off debugging, once enabled, inside the same block.
-
-=head2 Non-Capturing Regular Expression Flag
-
-Regular expressions now support a C</n> flag that disables capturing
-and filling in C<$1>, C<$2>, etc... inside of groups:
-
- "hello" =~ /(hi|hello)/n; # $1 is not set
-
-This is equivalent to putting C<?:> at the beginning of every capturing group.
-
-See L<perlre/"n"> for more information.
-
-=head2 C<use re 'strict'>
-
-This applies stricter syntax rules to regular expression patterns
-compiled within its scope, which hopefully will alert you to typos and
-other unintentional behavior that backwards-compatibility issues prevent
-us from doing in normal regular expression compilations. Because the
-behavior of this is subject to change in future Perl releases as we gain
-experience, using this pragma will raise a category
-C<experimental::re_strict> warning.
-See L<'strict' in re|re/'strict' mode>.
-
-=head2 C<qr/foo/x> now ignores any Unicode pattern white space
-
-The C</x> regular expression modifier allows the pattern to contain
-white space and comments, both of which are ignored, for improved
-readability. Until now, not all the white space characters that Unicode
-designates for this purpose were handled. The additional ones now
-recognized are
-U+0085 NEXT LINE,
-U+200E LEFT-TO-RIGHT MARK,
-U+200F RIGHT-TO-LEFT MARK,
-U+2028 LINE SEPARATOR,
-and
-U+2029 PARAGRAPH SEPARATOR.
-
-=head2 Unicode 7.0 (with correction) is now supported
-
-For details on what is in this release, see
-L<http://www.unicode.org/versions/Unicode7.0.0/>.
-The version of Unicode 7.0 that comes with Perl includes
-a correction dealing with glyph shaping in Arabic
-(see L<http://www.unicode.org/errata/#current_errata>).
-
-
-=head2 S<C<use locale>> can restrict which locale categories are affected
-
-It is now possible to pass a parameter to S<C<use locale>> to specify
-a subset of locale categories to be locale-aware, with the remaining
-ones unaffected. See L<perllocale/The "use locale" pragma> for details.
-
-=head2 Perl now supports POSIX 2008 locale currency additions
-
-On platforms that are able to handle POSIX.1-2008, the
-hash returned by
-L<C<POSIX::localeconv()>|perllocale/The localeconv function>
-includes the international currency fields added by that version of the
-POSIX standard. These are
-C<int_n_cs_precedes>,
-C<int_n_sep_by_space>,
-C<int_n_sign_posn>,
-C<int_p_cs_precedes>,
-C<int_p_sep_by_space>,
-and
-C<int_p_sign_posn>.
-
-=head2 Better heuristics on older platforms for determining locale UTF8ness
-
-On platforms that implement neither the C99 standard nor the POSIX 2001
-standard, determining if the current locale is UTF8 or not depends on
-heuristics. These are improved in this release.
-
-=head2 Aliasing via reference
-
-Variables and subroutines can now be aliased by assigning to a reference:
-
- \$c = \$d;
- \&x = \&y;
-
-Or by using a backslash before a C<foreach> iterator variable, which is
-perhaps the most useful idiom this feature provides:
-
- foreach \%hash (@array_of_hash_refs) { ... }
-
-This feature is experimental and must be enabled via C<use feature
-'refaliasing'>. It will warn unless the C<experimental::refaliasing>
-warnings category is disabled.
-
-See L<perlref/Assigning to References>
-
-=head2 C<prototype> with no arguments
-
-C<prototype()> with no arguments now infers C<$_>.
-L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
-
-=head2 New "const" subroutine attribute
-
-The "const" attribute can be applied to an anonymous subroutine. It causes
-it to be executed immediately when it is cloned. Its value is captured and
-used to create a new constant subroutine that is returned. This feature is
-experimental. See L<perlsub/Constant Functions>.
-
-=head2 C<fileno> now works on directory handles
-
-When the relevant support is available in the operating system, the
-C<fileno> builtin now works on directory handles, yielding the
-underlying file descriptor in the same way as for filehandles. On
-operating systems without such support, C<fileno> on a directory handle
-continues to return the undefined value, as before, but also sets C<$!> to
-indicate that the operation is not supported.
-
-Currently, this uses either a C<dd_fd> member in the OS C<DIR>
-structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
-
-=head2 List form of pipe open implemented for Win32
-
-The list form of pipe:
-
- open my $fh, "-|", "program", @arguments;
-
-is now implemented on Win32. It has the same limitations as C<system
-LIST> on Win32, since the Win32 API doesn't accept program arguments
-as a list.
-
-=head2 C<close> now sets C<$!>
-
-When an I/O error occurs, the fact that there has been an error is recorded
-in the handle. C<close> returns false for such a handle. Previously, the
-value of C<$!> would be untouched by C<close>, so the common convention of
-writing S<C<close $fh or die $!>> did not work reliably. Now the handle
-records the value of C<$!>, too, and C<close> restores it.
-
-=head2 Assignment to list repetition
-
-C<(...) x ...> can now be used within a list that is assigned to, as long
-as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
-= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
-
-=head2 Infinity and NaN (not-a-number) handling improved
-
-Floating point values are able to hold the special values infinity (also
--infinity), and NaN (not-a-number). Now we more robustly recognize and
-propagate the value in computations, and on output normalize them to C<Inf> and
-C<NaN>.
-
-See also the L<POSIX> enhancements.
-
-=head2 Floating point parsing has been improved
-
-Parsing and printing of floating point values has been improved.
-
-As a completely new feature, hexadecimal floating point literals
-(like C<0x1.23p-4>) are now supported, and they can be output with
-C<printf %a>.
-
-=head2 Packing infinity or not-a-number into a character is now fatal
+If you are upgrading from an earlier release such as 5.22.0, first read
+L<perl5230delta>, which describes differences between 5.22.0 and 5.23.0.
-Before, when trying to pack infinity or not-a-number into a
-(signed) character, Perl would warn, and assumed you tried to
-pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
-C<< U+FFFD >> was returned.
+=head1 Notice
-But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
-result in a fatal error.
+XXX Any important notices here
-=head2 Experimental C Backtrace API
-
-Starting from Perl 5.21.1, on some platforms Perl supports retrieving
-the C level backtrace (similar to what symbolic debuggers like gdb do).
-
-The backtrace returns the stack trace of the C call frames,
-with the symbol names (function names), the object names (like "perl"),
-and if it can, also the source code locations (file:line).
+=head1 Core Enhancements
-The supported platforms are Linux and OS X (some *BSD might work at
-least partly, but they have not yet been tested).
+XXX New core language features go here. Summarize user-visible core language
+enhancements. Particularly prominent performance optimisations could go
+here, but most should go in the L</Performance Enhancements> section.
-The feature needs to be enabled with C<Configure -Dusecbacktrace>.
+[ List each enhancement as a =head2 entry ]
-Also included is a C API to retrieve backtraces.
+=head2 Postfix dereferencing is no longer experimental
-See L<perlhacktips/"C backtrace"> for more information.
+Using the C<postderef> and C<postderef_qq> features no longer emits a warning.
+Existing code that disables that warning category will continue to work. The
+C<5.24> feature bundle now includes those features.
=head1 Security
-=head2 Perl is now compiled with -fstack-protector-strong if available
-
-Perl has been compiled with the anti-stack-smashing option
-C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
-called C<-fstack-protector-strong>, if available.
-
-=head2 The L<Safe> module could allow outside packages to be replaced
-
-Critical bugfix: outside packages could be replaced. L<Safe> has
-been patched to 2.38 to address this.
-
-=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
-
-The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
-gcc 4.*, is now always used for compiling Perl, if available.
+XXX Any security-related notices go here. In particular, any security
+vulnerabilities closed should be noted here rather than in the
+L</Selected Bug Fixes> section.
-Note that this isn't necessarily a huge step since in many platforms
-the step had already been taken several years ago: many Linux
-distributions (like Fedora) have been using this option for Perl,
-and OS X has enforced the same for many years.
+[ List each security issue as a =head2 entry ]
=head1 Incompatible Changes
-=head2 Subroutine signatures moved before attributes
-
-The experimental sub signatures feature, as introduced in 5.20, parsed
-signatures after attributes. In this release, the positioning has been
-moved such that signatures occur after the subroutine name (if any) and
-before the attribute list (if any).
-
-=head2 C<&> and C<\&> prototypes accepts only subs
-
-The C<&> prototype character now accepts only anonymous subs (C<sub {...}>)
-and things beginning with C<\&>. Formerly it erroneously also allowed
-C<undef> and references to array, hashes, and lists.
-L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
-L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
-
-The C<\&> prototype was allowing subroutine calls, whereas now it only
-allows subroutines. C<&foo> is permitted. C<&foo()> and C<foo()> are not.
-L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
-
-=head2 C<use encoding> is now lexical
-
-The L<encoding> pragma's effect is now limited to lexical scope. This
-pragma is deprecated, but in the meantime, it could adversely affect
-unrelated modules that are included in the same program.
-
-=head2 List slices returning empty lists
-
-List slices return an empty list now only if the original list was empty
-(or if there are no indices). Formerly, a list slice would return an empty
-list if all indices fell outside the original list.
-L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
-
-=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
-
-This has been deprecated since v5.18.
-
-=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
-
-Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
-is now a fatal error. S<C<"use UNIVERSAL">> without any arguments is still
-allowed.
-
-=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
-
-In prior releases, failure to do this raised a deprecation warning.
-
-=head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
-now a fatal compilation error.
-
-These had been deprecated since v5.18.
-
-=head2 5 additional characters are treated as white space under C</x> in
-regex patterns (unless escaped)
-
-The use of these characters with C</x> outside bracketed character
-classes and when not preceded by a backslash has raised a deprecation
-warning since v5.18. Now they will be ignored. See L</"qr/foo/x">
-for the list of the five characters.
-
-=head2 Comment lines within S<C<(?[ ])>> now are ended only by a C<\n>
-
-S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
-as if C</x> is always enabled. But there was a difference, comment
-lines (following a C<#> character) were terminated by anything matching
-C<\R> which includes all vertical whitespace, such as form feeds. For
-consistency, this is now changed to match what terminates comment lines
-outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
-same as what terminates a heredoc string and formats.
-
-=head2 C<(?[...])> operators now follow standard Perl precedence
-
-This experimental feature allows set operations in regular expression patterns.
-Prior to this, the intersection operator had the same precedence as the other
-binary operators. Now it has higher precedence. This could lead to different
-outcomes than existing code expects (though the documentation has always noted
-that this change might happen, recommending fully parenthesizing the
-expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
-
-=head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
-
-Really old Perl let you omit the C<@> on array names and the C<%> on hash
-names in some spots. This has issued a deprecation warning since Perl
-5.000, and is no longer permitted.
+XXX For a release on a stable branch, this section aspires to be:
-=head2 C<"$!"> text is now in English outside C<"use locale"> scope
+ There are no changes intentionally incompatible with 5.XXX.XXX
+ If any exist, they are bugs, and we request that you submit a
+ report. See L</Reporting Bugs> below.
-Previously, the text, unlike almost everything else, always came out
-based on the current underlying locale of the program. (Also affected
-on some systems is C<"$^E>".) For programs that are unprepared to
-handle locale, this can cause garbage text to be displayed. It's better
-to display text that is translatable via some tool than garbage text
-which is much harder to figure out.
-
-=head2 C<"$!"> text will be returned in UTF-8 when appropriate
-
-The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
-when the text is actually non-ASCII UTF-8. This will enable programs
-that are set up to be locale-aware to properly output messages in the
-user's native language. Code that needs to continue the 5.20 and
-earlier behavior can do the stringification within the scopes of both
-S<C<'use bytes'>> and S<C<'use locale ":messages">>. No other Perl
-operations will
-be affected by locale; only C<$!> and C<$^E> stringification. The
-'bytes' pragma causes the UTF-8 flag to not be set, just as in previous
-Perl releases. This resolves
-L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
-
-=head2 Support for C<?PATTERN?> without explicit operator has been removed
-
-Starting regular expressions matching only once directly with the
-question mark delimiter is now a syntax error, so that the question mark
-can be available for use in new operators. Write C<m?PATTERN?> instead,
-explicitly using the C<m> operator: the question mark delimiter still
-invokes match-once behaviour.
-
-=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
-
-These have been deprecated since v5.6.1 and have raised deprecation
-warnings since v5.16.
-
-=head2 Using a hash or an array as a reference are now fatal errors
-
-For example, C<%foo-E<gt>{"bar"}> now causes a fatal compilation
-error. These have been deprecated since before v5.8, and have raised
-deprecation warnings since then.
-
-=head2 Changes to the C<*> prototype
-
-The C<*> character in a subroutine's prototype used to allow barewords to take
-precedence over most, but not all subroutines. It was never consistent and
-exhibited buggy behaviour.
-
-Now it has been changed, so subroutines always take precedence over barewords,
-which brings it into conformity with similarly prototyped built-in functions:
-
- sub splat(*) { ... }
- sub foo { ... }
- splat(foo); # now always splat(foo())
- splat(bar); # still splat('bar') as before
- close(foo); # close(foo())
- close(bar); # close('bar')
+[ List each incompatible change as a =head2 entry ]
=head1 Deprecations
-=head2 Setting C<${^ENCODING}> to anything but C<undef>
+XXX Any deprecated features, syntax, modules etc. should be listed here.
-This variable allows Perl scripts to be written in a non-ASCII,
-non-UTF-8 encoding. However, it affects all modules globally, leading
-to wrong answers and segmentation faults. New scripts should be written
-in UTF-8; old scripts should be converted to UTF-8, which is easily done
-with the L<encoding> pragma.
+=head2 Module removals
-=head2 C<< /\C/ >> character class
+XXX Remove this section if inapplicable.
-This character class, which matches a single byte, even if it appears
-in a multi-byte character has been deprecated. Matching single bytes
-in a multi-byte character breaks encapsulation, and can corrupt utf8
-strings.
+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.
-=head2 Use of non-graphic characters in single-character variable names
+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.
-The syntax for single-character variable names is more lenient than
-for longer variable names, allowing the one-character name to be a
-punctuation character or even invisible (a non-graphic). Perl v5.20
-deprecated the ASCII-range controls as such a name. Now, all
-non-graphic characters that formerly were allowed are deprecated.
-The practical effect of this occurs only when not under C<S<"use
-utf8">>, and affects just the C1 controls (code points 0x80 through
-0xFF), NO-BREAK SPACE, and SOFT HYPHEN.
+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.
-=head2 Inlining of C<sub () { $var }> with observable side-effects
-
-In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
-subroutine, capturing the value of C<$var> at the time the C<sub> expression
-is evaluated. This can break the closure behaviour in those cases where
-C<$var> is subsequently modified. The subroutine won't return the new value.
-
-This usage is now deprecated in those cases where the variable could be
-modified elsewhere. Perl detects those cases and emits a deprecation
-warning. Such code will likely change in the future and stop producing a
-constant.
-
-If your variable is only modified in the place where it is declared, then
-Perl will continue to make the sub inlinable with no warnings.
+=over
- sub make_constant {
- my $var = shift;
- return sub () { $var }; # fine
- }
+=item XXX
- sub make_constant_deprecated {
- my $var;
- $var = shift;
- return sub () { $var }; # deprecated
- }
+XXX Note that deprecated modules should be listed here even if they are listed
+as an updated module in the L</Modules and Pragmata> section.
- sub make_constant_deprecated2 {
- my $var = shift;
- log_that_value($var); # could modify $var
- return sub () { $var }; # deprecated
- }
+=back
-In the second example above, detecting that C<$var> is assigned to only once
-is too hard to detect. That it happens in a spot other than the C<my>
-declaration is enough for Perl to find it suspicious.
+[ List each other deprecation as a =head2 entry ]
-This deprecation warning happens only for a simple variable for the body of
-the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
-because it does not become part of the sub's body.) For more complex
-cases, such as S<C<sub () { do_something() if 0; $var }>> the behaviour has
-changed such that inlining does not happen if the variable is modifiable
-elsewhere. Such cases should be rare.
+=head1 Performance Enhancements
-=head2 Use of multiple /x regexp modifiers
+XXX Changes which enhance performance without changing behaviour go here.
+There may well be none in a stable release.
-It is now deprecated to say something like any of the following:
+[ List each enhancement as a =item entry ]
- qr/foo/xx;
- /(?xax:foo)/;
- use re qw(/amxx);
+=over 4
-That is, now C<x> should only occur once in any string of contiguous
-regular expression pattern modifiers. We do not believe there are any
-occurrences of this in all of CPAN. This is in preparation for a future
-Perl release having C</xx> mean to allow white-space for readability in
-bracketed character classes (those enclosed in square brackets:
-C<[...]>).
+=item *
-=head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
-deprecated
+XXX
-This non-graphic character is essentially indistinguishable from a
-regular space, and so should not be allowed. See
-L<charnames/CUSTOM ALIASES>.
+=back
-=head2 A literal C<"{"> should now be escaped in a pattern
+=head1 Modules and Pragmata
-If you want a literal left curly bracket (also called a left brace) in a
-regular expression pattern, you should now escape it by either
-preceding it with a backslash (C<"\{">) or enclosing it within square
-brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
-will be raised. This was first announced as forthcoming in the v5.16
-release; it will allow future extensions to the language to happen.
+XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
+go here. If Module::CoreList is updated, generate an initial draft of the
+following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
+for important changes should then be added by hand. In an ideal world,
+dual-life modules would have a F<Changes> file that could be cribbed.
-=head2 Making all warnings fatal is discouraged
-
-The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
-C<< use warnings FATAL => 'all' >> is discouraged and provides stronger
-language about the risks of fatal warnings in general.
+[ Within each section, list entries as a =item entry ]
-=head1 Performance Enhancements
+=head2 New Modules and Pragmata
=over 4
=item *
-If method and class names are known at compile time, hashes are precomputed
-to speed up run-time method lookup. Also, compound method names like
-C<SUPER::new> are parsed at compile time, to save having to parse them at
-run time.
-
-=item *
-
-Array and hash lookups (especially nested ones) that use only constants
-or simple variables as keys, are now considerably faster. See
-L</Internal Changes> for more details.
-
-=item *
+XXX
-C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
-context. If the right-hand argument is a constant 1, the repetition
-operator disappears. If the right-hand argument is a constant 0, the whole
-expression is optimised to the empty list, so long as the left-hand
-argument is a simple scalar or constant. C<(foo())x0> is not optimised.
+=back
-=item *
+=head2 Updated Modules and Pragmata
-C<substr> assignment is now optimised into 4-argument C<substr> at the end
-of a subroutine (or as the argument to C<return>). Previously, this
-optimisation only happened in void context.
+=over 4
=item *
-Assignment to lexical variables is often optimised away. For instance, in
-C<$lexical = chr $foo>, the C<chr> operator writes directly to the lexical
-variable instead of returning a value that gets copied. This optimisation
-has been extended to C<split>, C<x> and C<vec> on the right-hand side. It
-has also been made to work with state variable initialization.
-
-=item *
+L<XXX> has been upgraded from version A.xx to B.yy.
-In "C<\L>...", "C<\Q>...", etc., the extra "stringify" op is now optimised away,
-making these just as fast as C<lcfirst>, C<quotemeta>, etc.
+=back
-=item *
+=head2 Removed Modules and Pragmata
-Assignment to an empty list is now sometimes faster. In particular, it
-never calls C<FETCH> on tied arguments on the right-hand side, whereas it
-used to sometimes.
+=over 4
=item *
-C<length> is up to 20% faster for non-magical/non-tied scalars containing a
-string if it is a non-utf8 string or if is in scope of C<use bytes>.
-
-=item *
+XXX
-Non-magical/non-tied scalars that contain only a floating point value and are
-on most Perl builds with 64 bit integers now use 8-32 less bytes of memory
-depending on OS.
+=back
-=item *
+=head1 Documentation
-In C<@array = split>, the assignment can be optimized away with C<split>
-writing directly to the array. This optimisation was happening only for
-package arrays other than C<@_> and only
-sometimes. Now this optimisation happens
-almost all the time.
+XXX Changes to files in F<pod/> go here. Consider grouping entries by
+file and be sure to link to the appropriate page, e.g. L<perlfunc>.
-=item *
+=head2 New Documentation
-C<join> is now subject to constant folding. Moreover, C<join> with a
-scalar or constant for the separator and a single-item list to join is
-simplified to a stringification. The separator doesn't even get evaluated.
+XXX Changes which create B<new> files in F<pod/> go here.
-=item *
+=head3 L<XXX>
-C<qq(@array)> is implemented using two ops: a stringify op and a join op.
-If the C<qq> contains nothing but a single array, the stringification is
-optimized away.
+XXX Description of the purpose of the new file here
-=item *
+=head2 Changes to Existing Documentation
-S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
-run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
-skipped over. The same applies to C<state> variables.
+XXX Changes which significantly change existing files in F<pod/> go here.
+However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
+section.
-=item *
+=head3 L<XXX>
-Many internal functions have been refactored to improve performance and reduce
-their memory footprints.
-L<[perl #121436]|https://rt.perl.org/Ticket/Display.html?id=121436>
-L<[perl #121906]|https://rt.perl.org/Ticket/Display.html?id=121906>
-L<[perl #121969]|https://rt.perl.org/Ticket/Display.html?id=121969>
+=over 4
=item *
-C<-T> and C<-B> filetests will return sooner when an empty file is detected.
-L<[perl #121489]|https://rt.perl.org/Ticket/Display.html?id=121489>
+XXX Description of the change here
-=item *
+=back
-Refactoring of C<< pp_tied >> and C<< pp_ref >> for small improvements.
+=head1 Diagnostics
-=item *
+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>.
-Pathtools don't try to load XS on miniperl.
+XXX New or changed warnings emitted by the core's C<C> code go here. Also
+include any changes in L<perldiag> that reconcile it to the C<C> code.
-=item *
+=head2 New Diagnostics
-A typo fix reduces the size of the C<< OP >> structure.
+XXX Newly added diagnostic messages go under here, separated into New Errors
+and New Warnings
-=item *
+=head3 New Errors
-Hash lookups where the key is a constant are faster.
+=over 4
=item *
-Subroutines with an empty prototype and bodies containing just C<undef> are now
-eligible for inlining.
-L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
-
-=item *
+XXX L<message|perldiag/"message">
-Subroutines in packages no longer need to carry typeglobs around with them.
-Declaring a subroutine will now put a simple sub reference in the stash if
-possible, saving memory. The typeglobs still notionally exist, so accessing
-them will cause the subroutine reference to be upgraded to a typeglob. This
-optimization does not currently apply to XSUBs or exported subroutines, and
-method calls will undo it, since they cache things in typeglobs.
-L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
+=back
-=item *
+=head3 New Warnings
-The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
-(see L<utf8>) are now optimized out on ASCII platforms. There is now not even
-a minimal performance hit in writing code portable between ASCII and EBCDIC
-platforms.
+=over 4
=item *
-Win32 Perl uses 8 KB less of per-process memory than before for every perl
-process of this version. This data is now memory mapped from disk and shared
-between perl processes from the same perl binary.
+XXX L<message|perldiag/"message">
=back
-=head1 Modules and Pragmata
-
-XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
-go here. If Module::CoreList is updated, generate an initial draft of the
-following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
-for important changes should then be added by hand. In an ideal world,
-dual-life modules would have a F<Changes> file that could be cribbed.
-
-[ Within each section, list entries as a =item entry ]
+=head2 Changes to Existing Diagnostics
-=head2 New Modules and Pragmata
+XXX Changes (i.e. rewording) of diagnostic messages go here
=over 4
=item *
-XXX
+XXX Describe change here
=back
-=head2 Updated Modules and Pragmata
-
-=over 4
-
-=item *
+=head1 Utility Changes
-L<XXX> has been upgraded from version A.xx to B.yy.
+XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
+Most of these are built within the directory F<utils>.
-=back
+[ List utility changes as a =head2 entry for each utility and =item
+entries for each change
+Use L<XXX> with program names to get proper documentation linking. ]
-=head2 Removed Modules and Pragmata
+=head2 L<XXX>
=over 4
=back
-=head1 Documentation
-
-=head2 New Documentation
-
-=head3 L<perlunicook>
-
-This document, by Tom Christiansen, provides examples of handling Unicode in
-Perl.
+=head1 Configuration and Compilation
-=head2 Changes to Existing Documentation
+XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
+go here. Any other changes to the Perl build process should be listed here.
+However, any platform-specific changes should be listed in the
+L</Platform Support> section, instead.
-=head3 L<perlapi>
+[ List changes as a =item entry ].
=over 4
=item *
-Note that C<SvSetSV> doesn't do set magic.
+XXX
-=item *
+=back
-C<sv_usepvn_flags> - Fix documentation to mention the use of C<NewX> instead of
-C<malloc>.
+=head1 Testing
-L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
+XXX Any significant changes to the testing of a freshly built perl should be
+listed here. Changes which create B<new> files in F<t/> go here as do any
+large changes to the testing harness (e.g. when parallel testing was added).
+Changes to existing files in F<t/> aren't worth summarizing, although the bugs
+that they represent may be covered elsewhere.
-=item *
+[ List each test improvement as a =item entry ]
-Clarify where C<NUL> may be embedded or is required to terminate a string.
+=over 4
=item *
-Previously missing documentation due to formatting errors are now included.
+XXX
-=item *
+=back
-Entries are now organized into groups rather than by file where they are found.
+=head1 Platform Support
-=item *
+XXX Any changes to platform support should be listed in the sections below.
-Alphabetical sorting of entries is now handled by the POD generator to make
-entries easier to find when scanning.
+[ Within the sections, list each platform as a =item entry with specific
+changes as paragraphs below it. ]
-=back
+=head2 New Platforms
-=head3 L<perldata>
+XXX List any platforms that this version of perl compiles on, that previous
+versions did not. These will either be enabled by new files in the F<hints/>
+directories, or new subdirectories and F<README> files at the top level of the
+source tree.
=over 4
-=item *
+=item XXX-some-platform
-The syntax of single-character variable names has been brought
-up-to-date and more fully explained.
+XXX
=back
-=head3 L<perlebcdic>
+=head2 Discontinued Platforms
+
+XXX List any platforms that this version of perl no longer compiles on.
=over 4
-=item *
+=item XXX-some-platform
-This document has been significantly updated in the light of recent
-improvements to EBCDIC support.
+XXX
=back
-=head3 L<perlfunc>
-
-=over 4
-
-=item *
-
-Mention that C<study()> is currently a no-op.
+=head2 Platform-Specific Notes
-=item *
+XXX List any changes for specific platforms. This could include configuration
+and compilation changes or changes in portability/compatibility. However,
+changes within modules for platforms should generally be listed in the
+L</Modules and Pragmata> section.
-Calling C<delete> or C<exists> on array values is now described as "strongly
-discouraged" rather than "deprecated".
+=over 4
-=item *
+=item VMS
-Improve documentation of C<< our >>.
+=over
=item *
-C<-l> now notes that it will return false if symlinks aren't supported by the
-file system.
+The minimum supported version of VMS is now v7.3-2, released in 2003. As a
+side effect of this change, VAX is no longer supported as the terminal
+release of OpenVMS VAX was v7.3 in 2001.
-L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
-
-=item *
-
-Note that C<exec LIST> and C<system LIST> may fall back to the shell on
-Win32. Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object
-syntax will reliably avoid using the shell.
+=back
-This has also been noted in L<perlport>.
+=back
-L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
+=head1 Internal Changes
-=back
+XXX Changes which affect the interface available to C<XS> code go here. Other
+significant internal changes for future core maintainers should be noted as
+well.
-=head3 L<perlguts>
+[ List each change as a =item entry ]
=over 4
=item *
-The OOK example has been updated to account for COW changes and a change in the
-storage of the offset.
+XXX
+
+=back
-=item *
+=head1 Selected Bug Fixes
-Details on C level symbols and libperl.t added.
+XXX Important bug fixes in the core language are summarized here. Bug fixes in
+files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
-=item *
+[ List each fix as a =item entry ]
-Information on Unicode handling has been added
+=over 4
=item *
-Information on EBCDIC handling has been added
+XXX
=back
-=head3 L<perlhacktips>
-
-=over 4
-
-=item *
+=head1 Known Problems
-Documentation has been added illustrating the perils of assuming the contents
-of static memory pointed to by the return values of Perl wrappers for C library
-functions doesn't change.
+XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
+tests that had to be C<TODO>ed for the release would be noted here. Unfixed
+platform specific bugs also go here.
-=item *
+[ List each fix as a =item entry ]
-Recommended replacements for tmpfile, atoi, strtol, and strtoul added.
+=over 4
=item *
-Updated documentation for the C<test.valgrind> C<make> target.
-
-L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
+XXX
=back
-=head3 L<perlmodstyle>
+=head1 Errata From Previous Releases
=over 4
=item *
-Instead of pointing to the module list, we are now pointing to
-L<PrePAN|http://prepan.org/>.
+XXX Add anything here that we forgot to add, or were mistaken about, in
+the perldelta of a previous release.
=back
-=head3 L<perlpolicy>
+=head1 Obituary
-=over 4
-
-=item *
-
-We now have a code of conduct for the I<< p5p >> mailing list, as documented
-in L<< perlpolicy/STANDARDS OF CONDUCT >>.
-
-=item *
-
-The conditions for marking an experimental feature as non-experimental are now
-set out.
-
-=back
-
-=head3 L<perlport>
-
-=over 4
-
-=item *
-
-Out-of-date VMS-specific information has been fixed/simplified.
-
-=item *
-
-Notes about EBCDIC have been added.
-
-=back
-
-=head3 L<perlre>
-
-=over 4
-
-=item *
-
-The C</x> modifier has been clarified to note that comments cannot be continued
-onto the next line by escaping them.
-
-=back
-
-=head3 L<perlrebackslash>
-
-=over 4
-
-=item *
-
-Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
-
-=back
-
-=head3 L<perlrecharclass>
-
-=over 4
-
-=item *
-
-Clarifications have been added to L<perlrecharclass/Character Ranges>
-to the effect that Perl guarantees that C<[A-Z]>, C<[a-z]>, C<[0-9]> and
-any subranges thereof in regular expression bracketed character classes
-are guaranteed to match exactly what a naive English speaker would
-expect them to match, even on platforms (such as EBCDIC) where special
-handling is required to accomplish this.
-
-=item *
-
-The documentation of Bracketed Character Classes has been expanded to cover the
-improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
-
-=back
-
-=head3 L<perlsec>
-
-=over 4
-
-=item *
-
-Comments added on algorithmic complexity and tied hashes.
-
-=back
-
-=head3 L<perlsyn>
-
-=over 4
-
-=item *
-
-An ambiguity in the documentation of the C<...> statement has been corrected.
-L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
-
-=item *
-
-The empty conditional in C<< for >> and C<< while >> is now documented
-in L<< perlsyn >>.
-
-=back
-
-=head3 L<perlunicode>
-
-=over 4
-
-=item *
-
-This has had extensive revisions to bring it up-to-date with current
-Unicode support and to make it more readable.
-
-=back
-
-=head3 L<perluniintro>
-
-=over 4
-
-=item *
-
-Advice for how to make sure your strings and regular expression patterns are
-interpreted as Unicode has been updated.
-
-=back
-
-=head3 L<perlvar>
-
-=over 4
-
-=item *
-
-Further clarify version number representations and usage.
-
-=back
-
-=head3 L<perlvms>
-
-=over 4
-
-=item *
-
-Out-of-date and/or incorrect material has been removed.
-
-=item *
-
-Updated documentation on environment and shell interaction in VMS.
-
-=back
-
-=head3 L<perlxs>
-
-=over 4
-
-=item *
-
-Added a discussion of locale issues in XS code.
-
-=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 New Diagnostics
-
-=head3 New Errors
-
-=over 4
-
-=item *
-
-L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
-
-(P) An internal request asked to add a scalar entry to something that
-wasn't a symbol table entry.
-
-=item *
-
-L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
-
-(F) You tried to use a hash as a reference, as in
-C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
-used to allow this syntax, but shouldn't have.
-
-=item *
-
-L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
-
-(F) You tried to use an array as a reference, as in
-C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
-allow this syntax, but shouldn't have.
-
-=item *
-
-L<Can't use 'defined(@array)' (Maybe you should just omit the defined()?)|perldiag/"Can't use 'defined(@array)' (Maybe you should just omit the defined()?)">
-
-(F) C<defined()> is not useful on arrays because it
-checks for an undefined I<scalar> value. If you want to see if the
-array is empty, just use S<C<if (@array) { # not empty }>> for example.
-
-=item *
-
-L<Can't use 'defined(%hash)' (Maybe you should just omit the defined()?)|perldiag/"Can't use 'defined(%hash)' (Maybe you should just omit the defined()?)">
-
-(F) C<defined()> is not usually right on hashes.
-
-Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
-becomes true in several non-obvious circumstances, including iterators,
-weak references, stash names, even remaining true after S<C<undef %hash>>.
-These things make S<C<defined %hash>> fairly useless in practice, so it now
-generates a fatal error.
-
-If a check for non-empty is what you wanted then just put it in boolean
-context (see L<perldata/Scalar values>):
-
- if (%hash) {
- # not empty
- }
-
-If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
-variable exists then that's never really been reliable, and isn't
-a good way to enquire about the features of a package, or whether
-it's loaded, etc.
-
-=item *
-
-L<Cannot chr %f|perldiag/"Cannot chr %f">
-
-(F) You passed an invalid number (like an infinity or not-a-number) to
-C<chr>.
-
-=item *
-
-L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
-
-(F) You tried converting an infinity or not-a-number to an unsigned
-character, which makes no sense.
-
-=item *
-
-L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
-
-(F) You tried converting an infinity or not-a-number to a character,
-which makes no sense.
-
-=item *
-
-L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
-
-(F) You tried printing an infinity or not-a-number as a character (C<%c>),
-which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
-
-=item *
-
-L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
-
-(F) You defined a character name which had multiple space
-characters in a row. Change them to single spaces. Usually these
-names are defined in the C<:alias> import argument to C<use charnames>, but
-they could be defined by a translator installed into C<$^H{charnames}>.
-See L<charnames/CUSTOM ALIASES>.
-
-=item *
-
-L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
-
-(F) You defined a character name which ended in a space
-character. Remove the trailing space(s). Usually these names are
-defined in the C<:alias> import argument to C<use charnames>, but they
-could be defined by a translator installed into C<$^H{charnames}>.
-See L<charnames/CUSTOM ALIASES>.
-
-=item *
-
-L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
-
-(F) The "const" attribute causes an anonymous subroutine to be run and
-its value captured at the time that it is cloned. Names subroutines are
-not cloned like this, so the attribute does not make sense on them.
-
-=item *
-
-L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
-
-(F) Something went horribly bad in hexadecimal float handling.
-
-=item *
-
-L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
-
-(F) You have configured Perl to use long doubles but
-the internals of the long double format are unknown,
-therefore the hexadecimal float output is impossible.
-
-=item *
-
-L<Illegal suidscript|perldiag/"Illegal suidscript">
-
-(F) The script run under suidperl was somehow illegal.
-
-=item *
-
-L<In '(?...)', the '(' and '?' must be adjacent in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"In '(?...)', the '(' and '?' must be adjacent in regex; marked by <-- HERE in m/%s/">
-
-(F) The two-character sequence C<"(?"> in
-this context in a regular expression pattern should be an
-indivisible token, with nothing intervening between the C<"(">
-and the C<"?">, but you separated them.
-
-=item *
-
-L<In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked by <-- HERE in m/%s/">
-
-(F) The two-character sequence C<"(*"> in
-this context in a regular expression pattern should be an
-indivisible token, with nothing intervening between the C<"(">
-and the C<"*">, but you separated them.
-
-=item *
-
-L<Invalid quantifier in {,} in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Invalid quantifier in {,} in regex; marked by <-- HERE in m/%s/">
-
-(F) The pattern looks like a {min,max} quantifier, but the min or max could not
-be parsed as a valid number - either it has leading zeroes, or it represents
-too big a number to cope with. The S<<-- HERE> shows where in the regular
-expression the problem was discovered. See L<perlre>.
-
-=back
-
-=head3 New Warnings
-
-=over 4
-
-=item *
-
-L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
-
-You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
-Perl. The current valid ones are given in
-L<perlrebackslash/\b{}, \b, \B{}, \B>.
-
-=item *
-
-L<"%s" is more clearly written simply as "%s" in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"%s" is more clearly written simply as "%s" in regex; marked by <-- HERE in mE<sol>%sE<sol>>
-
-(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
-
-You specified a character that has the given plainer way of writing it,
-and which is also portable to platforms running with different character
-sets.
-
-=item *
-
-L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
-as 0 in increment (++)">
-
-(W numeric) The indicated string was fed as an argument to the C<++> operator
-which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
-See L<perlop/Auto-increment and Auto-decrement> for details.
-
-=item *
-
-L<Both or neither range ends should be Unicode in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Both or neither range ends should be Unicode in regex; marked by <-- HERE in m/%s/">
-
-(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
-
-In a bracketed character class in a regular expression pattern, you
-had a range which has exactly one end of it specified using C<\N{}>, and
-the other end is specified using a non-portable mechanism. Perl treats
-the range as a Unicode range, that is, all the characters in it are
-considered to be the Unicode characters, and which may be different code
-points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
-is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
-matches the characters whose code points in Unicode are 6, 7, and 8.
-But that C<\x08> might indicate that you meant something different, so
-the warning gets raised.
-
-=item *
-
-L<:const is experimental|perldiag/":const is experimental">
-
-(S experimental::const_attr) The "const" attribute is experimental.
-If you want to use the feature, disable the warning with C<no warnings
-'experimental::const_attr'>, but know that in doing so you are taking
-the risk that your code may break in a future Perl version.
-
-=item *
-
-L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
-
-(W overflow) You called C<gmtime> with a number that it could not handle:
-too large, too small, or NaN. The returned value is C<undef>.
-
-=item *
-
-L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
-
-(W overflow) The hexadecimal floating point has larger exponent
-than the floating point supports.
-
-=item *
-
-L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
-
-(W overflow) The hexadecimal floating point has smaller exponent
-than the floating point supports.
-
-=item *
-
-L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
-
-(W overflow) The hexadecimal floating point literal had more bits in
-the mantissa (the part between the 0x and the exponent, also known as
-the fraction or the significand) than the floating point supports.
-
-=item *
-
-L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
-
-(W overflow) The hexadecimal floating point had internally more
-digits than could be output. This can be caused by unsupported
-long double formats, or by 64-bit integers not being available
-(needed to retrieve the digits under some configurations).
-
-=item *
-
-L<localtime(%f) failed|perldiag/"localtime(%f) failed">
-
-(W overflow) You called C<localtime> with a number that it could not handle:
-too large, too small, or NaN. The returned value is C<undef>.
-
-=item *
-
-L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
-
-(W numeric) You tried to execute the
-L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
-times, which doesn't make sense.
-
-=item *
-
-L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
-
-(D deprecated) You defined a character name which contained a no-break
-space character. Change it to a regular space. Usually these names are
-defined in the C<:alias> import argument to C<use charnames>, but they
-could be defined by a translator installed into C<$^H{charnames}>. See
-L<charnames/CUSTOM ALIASES>.
-
-=item *
-
-L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
-
-(W numeric) You tried to execute the
-L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
-C<-Inf>) or C<NaN> times, which doesn't make sense.
-
-=item *
-
-L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
-
-(S experimental::win32_perlio) The C<:win32> PerlIO layer is
-experimental. If you want to take the risk of using this layer,
-simply disable this warning:
-
- no warnings "experimental::win32_perlio";
-
-=item *
-
-L<Ranges of ASCII printables should be some subset of "0-9", "A-Z", or "a-z" in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Ranges of ASCII printables should be some subset of "0-9", "A-Z", or "a-z" in regex; marked by <-- HERE in mE<sol>%sE<sol>">
-
-(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
-
-Stricter rules help to find typos and other errors. Perhaps you didn't
-even intend a range here, if the C<"-"> was meant to be some other
-character, or should have been escaped (like C<"\-">). If you did
-intend a range, the one that was used is not portable between ASCII and
-EBCDIC platforms, and doesn't have an obvious meaning to a casual
-reader.
-
- [3-7] # OK; Obvious and portable
- [d-g] # OK; Obvious and portable
- [A-Y] # OK; Obvious and portable
- [A-z] # WRONG; Not portable; not clear what is meant
- [a-Z] # WRONG; Not portable; not clear what is meant
- [%-.] # WRONG; Not portable; not clear what is meant
- [\x41-Z] # WRONG; Not portable; not obvious to non-geek
-
-(You can force portability by specifying a Unicode range, which means that
-the endpoints are specified by
-L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
-still not be obvious.)
-The stricter rules require that ranges that start or stop with an ASCII
-character that is not a control have all their endpoints be a literal
-character, and not some escape sequence (like C<"\x41">), and the ranges
-must be all digits, or all uppercase letters, or all lowercase letters.
-
-=item *
-
-L<Ranges of digits should be from the same group in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Ranges of digits should be from the same group in regex; marked by <-- HERE in m/%s/">
-
-(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
-
-Stricter rules help to find typos and other errors. You included a
-range, and at least one of the end points is a decimal digit. Under the
-stricter rules, when this happens, both end points should be digits in
-the same group of 10 consecutive digits.
-
-=item *
-
-L<Redundant argument in %s|perldiag/Redundant argument in %s>
-
-(W redundant) You called a function with more arguments than other
-arguments you supplied indicated would be needed. Currently only
-emitted when a printf-type format required fewer arguments than were
-supplied, but might be used in the future for e.g. L<perlfunc/pack>.
-
-The warnings category C<< redundant >> is new. See also
-L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
-
-=item *
-
-L<Use of \b{} for non-UTF-8 locale is wrong. Assuming a UTF-8 locale|perldiag/"Use of \b{} for non-UTF-8 locale is wrong. Assuming a UTF-8 locale">
-
-You are matching a regular expression using locale rules,
-and a Unicode boundary is being matched, but the locale is not a Unicode
-one. This doesn't make sense. Perl will continue, assuming a Unicode
-(UTF-8) locale, but the results could well be wrong except if the locale
-happens to be ISO-8859-1 (Latin1) where this message is spurious and can
-be ignored.
-
-=item *
-
-L<< Using E<sol>u for '%s' instead of E<sol>%s in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Using E<sol>u for '%s' instead of E<sol>%s in regex; marked by <-- HERE in mE<sol>%sE<sol>" >>
-
-You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
-portion of a regular expression where the character set modifiers C</a>
-or C</aa> are in effect. These two modifiers indicate an ASCII
-interpretation, and this doesn't make sense for a Unicode definition.
-The generated regular expression will compile so that the boundary uses
-all of Unicode. No other portion of the regular expression is affected.
-
-=item *
-
-L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
-
-This warning is emitted if you use bitwise
-operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
-Simply suppress the warning if you want to use the feature, but know
-that in doing so you are taking the risk of using an experimental
-feature which may change or be removed in a future Perl version:
-
- no warnings "experimental::bitwise";
- use feature "bitwise";
- $x |.= $y;
-
-=item *
-
-L<Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/%s/">
-
-(D deprecated, regexp) You used a literal C<"{"> character in a regular
-expression pattern. You should change to use C<"\{"> instead, because a future
-version of Perl (tentatively v5.26) will consider this to be a syntax error. If
-the pattern delimiters are also braces, any matching right brace
-(C<"}">) should also be escaped to avoid confusing the parser, for
-example,
-
- qr{abc\{def\}ghi}
-
-=item *
-
-L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
-
-=item *
-
-L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
-
-(W misc) The "const" attribute has no effect except
-on anonymous closure prototypes. You applied it to
-a subroutine via L<attributes.pm|attributes>. This is only useful
-inside an attribute handler for an anonymous subroutine.
-
-=item *
-
-L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
-
-(S experimental::re_strict) The things that are different when a regular
-expression pattern is compiled under C<'strict'> are subject to change
-in future Perl releases in incompatible ways. This means that a pattern
-that compiles today may not in a future Perl release. This warning is
-to alert you to that risk.
-
-=item *
-
-L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
-
-=item *
-
-L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
-
-(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
-one), a multi-byte character was encountered. Perl considers this
-character to be the specified Unicode code point. Combining non-UTF8
-locales and Unicode is dangerous. Almost certainly some characters
-will have two different representations. For example, in the ISO 8859-7
-(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
-also does 0x393. This will make string comparisons unreliable.
-
-You likely need to figure out how this multi-byte character got mixed up
-with your single-byte locale (or perhaps you thought you had a UTF-8
-locale, but Perl disagrees).
-
-=item *
-
-The following two warnings for C<tr///> used to be skipped if the
-transliteration contained wide characters, but now they occur regardless of
-whether there are wide characters or not:
-
-L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
-
-L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
-
-=item *
-
-A new C<locale> warning category has been created, with the following warning
-messages currently in it:
-
-=over 4
-
-=item *
-
-L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
-
-=item *
-
-L<Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".|perldiag/Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".>
-
-=back
-
-=back
-
-=head2 Changes to Existing Diagnostics
-
-=over 4
-
-=item *
-
-<> should be quotes
-
-This warning has been changed to
-L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
-to make the issue more identifiable.
-
-=item *
-
-L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
-now adds the following note:
-
- Note that for the Inf and NaN (infinity and not-a-number) the
- definition of "numeric" is somewhat unusual: the strings themselves
- (like "Inf") are considered numeric, and anything following them is
- considered non-numeric.
-
-=item *
-
-L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
-
-This message has had '(did you forget to declare "my %s"?)' appended to it, to
-make it more helpful to new Perl programmers.
-L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
-
-=item *
-
-'"my" variable &foo::bar can't be in a package' has been reworded to say
-'subroutine' instead of 'variable'.
-
-=item *
-
-L<\N{} in character class restricted to one character in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character class or as a range end-point is restricted to one character in regex; marked by <-- HERE in m/%s/">
-
-This message has had 'character class' changed to 'inverted character class or
-as a range end-point is' to reflect improvements in C<qr/[\N{named sequence}]/>
-(see under L</Selected Bug Fixes>).
-
-=item *
-
-L<panic: frexp|perldiag/"panic: frexp: %f">
-
-This message has had ': C<%f>' appended to it, to show what the offending floating
-point number is.
-
-=item *
-
-B<Possible precedence problem on bitwise %c operator> reworded as
-L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
-
-=item *
-
-C<require> with no argument or undef used to warn about a Null filename; now
-it dies with C<Missing or undefined argument to require>.
-
-=item *
-
-L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
-
-This warning is now only produced when the newline is at the end of
-the filename.
-
-=item *
-
-"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
-when it is actually a lexical sub that will not stay shared.
-
-=item *
-
-L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
-
-Information about Unicode behaviour has been added.
-
-=back
-
-=head2 Diagnostic Removals
-
-=over
-
-=item *
-
-"Ambiguous use of -foo resolved as -&foo()"
-
-There is actually no ambiguity here, and this impedes the use of negated
-constants; e.g., C<-Inf>.
-
-=item *
-
-"Constant is not a FOO reference"
-
-Compile-time checking of constant dereferencing (e.g., C<< my_constant->() >>)
-has been removed, since it was not taking overloading into account.
-L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
-L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
-
-=back
-
-=head1 Utility Changes
-
-=head2 F<x2p/>
-
-=over 4
-
-=item *
-
-The F<x2p/> directory has been removed from the Perl core.
-
-This removes find2perl, s2p and a2p. They have all been released to CPAN as
-separate distributions (App::find2perl, App::s2p, App::a2p).
-
-=back
-
-=head2 L<h2ph>
-
-=over 4
-
-=item *
-
-F<h2ph> now handles hexadecimal constants in the compiler's predefined
-macro definitions, as visible in C<$Config{cppsymbols}>.
-L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
-
-=back
-
-=head2 L<encguess>
-
-=over 4
-
-=item *
-
-No longer depends on non-core module anymore.
-
-=back
-
-=head1 Configuration and Compilation
-
-=over 4
-
-=item *
-
-F<Configure> now checks for F<lrintl>, F<lroundl>, F<llrintl>, and F<llroundl>.
-
-=item *
-
-F<Configure> with C<-Dmksymlinks> should now be faster.
-L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
-
-=item *
-
-pthreads and lcl will be linked by default if present. This allows XS modules
-that require threading to work on non-threaded perls. Note that you must still
-pass C<-Dusethreads> if you want a threaded perl.
-
-=item *
-
-For long doubles (to get more precision and range for floating point numbers)
-one can now use the GCC quadmath library which implements the quadruple
-precision floating point numbers in x86 and ia64 platforms. See F<INSTALL> for
-details.
-
-=item *
-
-MurmurHash64A and MurmurHash64B can now be configured as the internal hash
-function.
-
-=item *
-
-C<make test.valgrind> now supports parallel testing.
-
-For example:
-
- TEST_JOBS=9 make test.valgrind
-
-See L<perlhacktips/valgrind> for more information.
-
-L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
-
-=item *
-
-The MAD (Misc Attribute Decoration) build option has been removed
-
-This was an unmaintained attempt at preserving
-the Perl parse tree more faithfully so that automatic conversion of
-Perl 5 to Perl 6 would have been easier.
-
-This build-time configuration option had been unmaintained for years,
-and had probably seriously diverged on both Perl 5 and Perl 6 sides.
-
-=item *
-
-A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
-see the discussion below at L<< /Internal Changes >>.
-
-=back
-
-=head1 Testing
-
-=over 4
-
-=item *
-
-F<t/porting/re_context.t> has been added to test that L<utf8> and its
-dependencies only use the subset of the C<$1..$n> capture vars that
-C<Perl_save_re_context()> is hard-coded to localize, because that function has no
-efficient way of determining at runtime what vars to localize.
-
-=item *
-
-Tests for performance issues have been added in the file F<t/perf/taint.t>.
-
-=item *
-
-Some regular expression tests are written in such a way that they will
-run very slowly if certain optimizations break. These tests have been
-moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
-and are run with a C<< watchdog() >>.
-
-=item *
-
-C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
-more compatible with C<< Test::More >>.
-
-=item *
-
-A new test script, F<op/infnan.t>, has been added to test if Inf and NaN are
-working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
-
-=back
-
-=head1 Platform Support
-
-=head2 Regained Platforms
-
-=over 4
-
-=item IRIX and Tru64 platforms are working again.
-
-(Some C<make test> failures remain.)
-
-=item z/OS running EBCDIC Code Page 1047
-
-Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
-even though support wasn't officially withdrawn, recent perls would not compile
-and run well. Perl 5.20 would work, but had many bugs which have now been
-fixed. Many CPAN modules that ship with Perl still fail tests, including
-Pod::Simple. However the version of Pod::Simple currently on CPAN should work;
-it was fixed too late to include in Perl 5.22. Work is under way to fix many
-of the still-broken CPAN modules, which likely will be installed on CPAN when
-completed, so that you may not have to wait until Perl 5.24 to get a working
-version.
-
-=back
-
-=head2 Discontinued Platforms
-
-=over 4
-
-=item NeXTSTEP/OPENSTEP
-
-NeXTSTEP was proprietary OS bundled with NeXT's workstations in the early
-to mid 90s; OPENSTEP was an API specification that provided a NeXTSTEP-like
-environment on a non-NeXTSTEP system. Both are now long dead, so support
-for building Perl on them has been removed.
-
-=back
-
-=head2 Platform-Specific Notes
-
-=over 4
-
-=item EBCDIC
-
-Special handling is required on EBCDIC platforms to get C<qr/[i-j]/> to
-match only C<"i"> and C<"j">, since there are 7 characters between the
-code points for C<"i"> and C<"j">. This special handling had only been
-invoked when both ends of the range are literals. Now it is also
-invoked if any of the C<\N{...}> forms for specifying a character by
-name or Unicode code point is used instead of a literal. See
-L<perlrecharclass/Character Ranges>.
-
-=item HP-UX
-
-The archname now distinguishes use64bitint from use64bitall.
-
-=item Android
-
-Build support has been improved for cross-compiling in general and for
-Android in particular.
-
-=item VMS
-
-=over 4
-
-=item *
-
-When spawning a subprocess without waiting, the return value is now
-the correct PID.
-
-=item *
-
-Fix a prototype so linking doesn't fail under the VMS C++ compiler.
-
-=item *
-
-C<finite>, C<finitel>, and C<isfinite> detection has been added to
-C<configure.com>, environment handling has had some minor changes, and
-a fix for legacy feature checking status.
-
-=back
-
-=item Win32
-
-=over 4
-
-=item *
-
-F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
-builds to complete on GCC 4.8.
-L<[perl #123976]|https://rt.perl.org/Ticket/Display.html?id=123976>
-
-=item *
-
-C<test-prep> again depends on C<test-prep-gcc> for GCC builds.
-L<[perl #124221]|https://rt.perl.org/Ticket/Display.html?id=124221>
-
-=item *
-
-Perl can now be built in C++ mode on Windows by setting the makefile macro
-C<USE_CPLUSPLUS> to the value "define".
-
-=item *
-
-List form pipe open no longer falls back to the shell.
-
-=item *
-
-In release 5.21.8 compiling on VC with dmake was broken. Fixed.
-
-=item *
-
-New C<DebugSymbols> and C<DebugFull> configuration options added to
-Windows makefiles.
-
-=item *
-
-L<B> now compiles again on Windows.
-
-=item *
-
-Previously, on Visual C++ for Win64 built Perls only, when compiling every Perl
-XS module (including CPAN ones) and Perl aware .c file with a 64 bit Visual C++,
-would unconditionally have around a dozen warnings from hv_func.h. These
-warnings have been silenced. GCC all bitness and Visual C++ for Win32 were
-not affected.
-
-=item *
-
-Support for building without PerlIO has been removed from the Windows
-makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
-already not supported by F<Configure> on POSIX systems.
-
-=item *
-
-Between 2 and 6 ms and 7 I/O calls have been saved per attempt to open a perl
-module for each path in C<@INC>.
-
-=item *
-
-Intel C builds are now always built with C99 mode on.
-
-=item *
-
-C<%I64d> is now being used instead of C<%lld> for MinGW.
-
-=item *
-
-In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
-opening C</dev/null>, which works the Win32 Perl's normal C<:unix> layer, was
-implemented for C<:win32>.
-L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
-
-=item *
-
-A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
-dmake makefile for gcc builds only. Set this to "define" if you want perl to
-use long doubles to give more accuracy and range for floating point numbers.
-
-=back
-
-=item OpenBSD
-
-On OpenBSD, Perl will now default to using the system C<malloc> due to the
-security features it provides. Perl's own malloc wrapper has been in use
-since v5.14 due to performance reasons, but the OpenBSD project believes
-the tradeoff is worth it and would prefer that users who need the speed
-specifically ask for it.
-
-L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
-
-=item Solaris
-
-=over 4
-
-=item *
-
-We now look for the Sun Studio compiler in both F</opt/solstudio*> and
-F</opt/solarisstudio*>.
-
-=item *
-
-Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
-didn't follow implied dependencies to build C<perldtrace.h>. Added an
-explicit dependency to C<depend>.
-L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
-
-=item *
-
-C<c99> options have been cleaned up, hints look for C<solstudio>
-as well as C<SUNWspro>, and support for native C<setenv> has been added.
-
-=back
-
-=back
-
-=head1 Internal Changes
-
-=over 4
-
-=item *
-
-Experimental support has been added to allow ops in the optree to locate
-their parent, if any. This is enabled by the non-default build option
-C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
-enabled by default, so XS code which directly accesses the C<op_silbing>
-field of ops should be updated to be future-proofed.
-
-On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
-C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
-sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
-parent (if any) rather than to being C<NULL>.
-
-To make existing code work transparently whether using C<-DPERL_OP_PARENT>
-or not, a number of new macros and functions have been added that should
-be used, rather than directly manipulating C<op_sibling>.
-
-For the case of just reading C<op_sibling> to determine the next sibling,
-two new macros have been added. A simple scan through a sibling chain
-like this:
-
- for (; kid->op_sibling; kid = kid->op_sibling) { ... }
-
-should now be written as:
-
- for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
-
-For altering optrees, A general-purpose function C<op_sibling_splice()>
-has been added, which allows for manipulation of a chain of sibling ops.
-By analogy with the Perl function C<splice()>, it allows you to cut out
-zero or more ops from a sibling chain and replace them with zero or more
-new ops. It transparently handles all the updating of sibling, parent,
-op_last pointers etc.
-
-If you need to manipulate ops at a lower level, then three new macros,
-C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
-be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
-also updating C<op_moresib>. The first sets the sibling pointer to a new
-sibling, the second makes the op the last sibling, and the third
-conditionally does the first or second action. Note that unlike
-C<op_sibling_splice()> these macros won't maintain consistency in the
-parent at the same time (e.g. by updating C<op_first> and C<op_last> where
-appropriate).
-
-A C-level C<Perl_op_parent()> function and a perl-level C<B::OP::parent()>
-method have been added. The C function only exists under
-C<-DPERL_OP_PARENT> builds (using it is build-time error on vanilla
-perls). C<B::OP::parent()> exists always, but on a vanilla build it
-always returns C<NULL>. Under C<-DPERL_OP_PARENT>, they return the parent
-of the current op, if any. The variable C<$B::OP::does_parent> allows you
-to determine whether C<B> supports retrieving an op's parent.
-
-C<-DPERL_OP_PARENT> was introduced in 5.21.2, but the interface was
-changed considerably in 5.21.11. If you updated your code before the
-5.21.11 changes, it may require further revision. The main changes after
-5.21.2 were:
-
-=over 4
-
-=item *
-
-The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
-C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
-op-manipulating macros.
-
-=item *
-
-The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
-inverted.
-
-=item *
-
-The macro C<OpSIBLING_set> has been removed, and has been superseded by
-C<OpMORESIB_set> et al.
-
-=item *
-
-The C<op_sibling_splice()> function now accepts a null C<parent> argument
-where the splicing doesn't affect the first or last ops in the sibling
-chain
-
-=back
-
-=item *
-
-Macros have been created to allow XS code to better manipulate the POSIX locale
-category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
-
-=item *
-
-The previous C<atoi> et al replacement function, C<grok_atou>, has now been
-superseded by C<grok_atoUV>. See L<perlclib> for details.
-
-=item *
-
-Added C<Perl_sv_get_backrefs()> to determine if an SV is a weak-referent.
-
-Function either returns an SV * of type AV, which contains the set of
-weakreferences which reference the passed in SV, or a simple RV * which
-is the only weakref to this item.
-
-=item *
-
-C<screaminstr> has been removed. Although marked as public API, it is
-undocumented and has no usage in modern perl versions on CPAN Grep. Calling it
-has been fatal since 5.17.0.
-
-=item *
-
-C<newDEFSVOP>, C<block_start>, C<block_end> and C<intro_my> have been added
-to the API.
-
-=item *
-
-The internal C<convert> function in F<op.c> has been renamed
-C<op_convert_list> and added to the API.
-
-=item *
-
-C<sv_magic> no longer forbids "ext" magic on read-only values. After all,
-perl can't know whether the custom magic will modify the SV or not.
-L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
-
-=item *
-
-Starting in 5.21.6, accessing L<perlapi/CvPADLIST> in an XSUB is forbidden.
-CvPADLIST has been reused for a different internal purpose for XSUBs. Guard all
-CvPADLIST expressions with C<CvISXSUB()> if your code doesn't already block
-XSUB CV*s from going through optree CV* expecting code.
-
-=item *
-
-SVs of type SVt_NV are now bodyless when a build configure and platform allow
-it, specifically C<sizeof(NV) <= sizeof(IV)>. The bodyless trick is the same one
-as for IVs since 5.9.2, but for NVs, unlike IVs, is not guaranteed on all
-platforms and build configurations.
-
-=item *
-
-The C<$DB::single>, C<$DB::signal> and C<$DB::trace> now have set and
-get magic that stores their values as IVs and those IVs are used when
-testing their values in C<pp_dbstate>. This prevents perl from
-recursing infinity if an overloaded object is assigned to any of those
-variables.
-L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
-
-=item *
-
-C<Perl_tmps_grow> which is marked as public API but undocumented has been
-removed from public API. If you use C<EXTEND_MORTAL> macro in your XS code to
-preextend the mortal stack, you are unaffected by this change.
-
-=item *
-
-C<cv_name>, which was introduced in 5.21.4, has been changed incompatibly.
-It now has a flags field that allows the caller to specify whether the name
-should be fully qualified. See L<perlapi/cv_name>.
-
-=item *
-
-Internally Perl no longer uses the C<SVs_PADMY> flag. C<SvPADMY()> now
-returns a true value for anything not marked PADTMP. C<SVs_PADMY> is now
-defined as 0.
-
-=item *
-
-The macros SETsv and SETsvUN have been removed. They were no longer used
-in the core since commit 6f1401dc2a, and have not been found present on
-CPAN.
-
-=item *
-
-The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
-David Mitchell for future work on vtables.
-
-=item *
-
-The C<sv_catpvn_flags> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
-flags, which specify whether the appended string is bytes or utf8,
-respectively.
-
-=item *
-
-A new opcode class, C<< METHOP >> has been introduced, which holds
-class/method related info needed at runtime to improve performance
-of class/object method calls.
-
-C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> are moved from being
-C<< UNOP/SVOP >> to being C<< METHOP >>.
-
-=item *
-
-C<save_re_context> no longer does anything and has been moved to F<mathoms.c>.
-
-=item *
-
-C<cv_name> is a new API function that can be passed a CV or GV. It returns an
-SV containing the name of the subroutine for use in diagnostics.
-L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
-L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
-
-=item *
-
-C<cv_set_call_checker_flags> is a new API function that works like
-C<cv_set_call_checker>, except that it allows the caller to specify whether the
-call checker requires a full GV for reporting the subroutine's name, or whether
-it could be passed a CV instead. Whatever value is passed will be acceptable
-to C<cv_name>. C<cv_set_call_checker> guarantees there will be a GV, but it
-may have to create one on the fly, which is inefficient.
-L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
-
-=item *
-
-C<CvGV> (which is not part of the API) is now a more complex macro, which may
-call a function and reify a GV. For those cases where is has been used as a
-boolean, C<CvHASGV> has been added, which will return true for CVs that
-notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
-now for lexical subs.
-L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
-
-=item *
-
-Added L<perlapi/sync_locale>. Changing the program's locale should be avoided
-by XS code. Nevertheless, certain non-Perl libraries called from XS, such as
-C<Gtk> do so. When this happens, Perl needs to be told that the locale has
-changed. Use this function to do so, before returning to Perl.
-
-=item *
-
-The defines and labels for the flags in the C<op_private> field of OPs are now
-auto-generated from data in F<regen/op_private>. The noticeable effect of this
-is that some of the flag output of C<Concise> might differ slightly, and the
-flag output of C<perl -Dx> may differ considerably (they both use the same set
-of labels now). Also in debugging builds, there is a new assert in
-C<op_free()> that checks that the op doesn't have any unrecognized flags set in
-C<op_private>.
-
-=item *
-
-The deprecated variable C<PL_sv_objcount> has been removed.
-
-=item *
-
-Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
-except around operations that need it to be set to the program's
-underlying locale. This protects the many XS modules that cannot cope
-with the decimal radix character not being a dot. Prior to this
-release, Perl initialized this category to "C", but a call to
-C<POSIX::setlocale()> would change it. Now such a call will change the
-underlying locale of the C<LC_NUMERIC> category for the program, but the
-locale exposed to XS code will remain "C". There are new macros
-to manipulate the LC_NUMERIC locale, including
-C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
-C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
-See L<perlapi/Locale-related functions and macros>.
-
-=item *
-
-A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
-efficiently determines if the string given by its parameters begins
-with a well-formed UTF-8 encoded character.
-
-=item *
-
-The following private API functions had their context parameter removed,
-C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
-C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
-C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
-
-Users of the public API prefix-less calls remain unaffected.
-
-=item *
-
-The PADNAME and PADNAMELIST types are now separate types, and no longer
-simply aliases for SV and AV.
-L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
-
-=item *
-
-Pad names are now always UTF8. The C<PadnameUTF8> macro always returns
-true. Previously, this was effectively the case already, but any support
-for two different internal representations of pad names has now been
-removed.
-
-=item *
-
-A new op class, C<UNOP_AUX>, has been added. This is a subclass of
-C<UNOP> with an C<op_aux> field added, which points to an array of unions
-of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
-than a simple C<op_sv> or whatever. Currently the only op of this type is
-C<OP_MULTIDEREF> (see below).
-
-=item *
-
-A new op has been added, C<OP_MULTIDEREF>, which performs one or more
-nested array and hash lookups where the key is a constant or simple
-variable. For example the expression C<$a[0]{$k}[$i]>, which previously
-involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
-by a single C<multideref> op. It can also handle C<local>, C<exists> and
-C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
-using C<aelem>/C<helem>, and single-level array lookup with a small constant
-index is still done using C<aelemfast>.
-
-=back
-
-=head1 Selected Bug Fixes
-
-=over 4
-
-=item *
-
-C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long double
-builds. GCC 4.8 and later, under some build options, would either overwrite
-the zero-initialized padding, or bypass the initialized buffer entirely. This
-caused F<op/pack.t> to fail.
-L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
-
-=item *
-
-Extending an array cloned from a parent thread could result in "Modification of
-a read-only value attempted" errors when attempting to modify the new elements.
-L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
-
-=item *
-
-An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
-L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
-
-=item *
-
-An optimization for state variable initialization introduced in Perl 5.21.6 has
-been reverted because it was found to exacerbate some other existing buggy
-behaviour.
-L<[perl #124160]|https://rt.perl.org/Ticket/Display.html?id=124160>
-
-=item *
-
-The extension of another optimization to cover more ops in Perl 5.21 has also
-been reverted to its Perl 5.20 state as a temporary fix for regression issues
-that it caused.
-L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
-
-=item *
-
-New bitwise ops added in Perl 5.21.9 accidentally caused C<$^H |= 0x1c020000>
-to enable all features. This has now been fixed.
-
-=item *
-
-A possible crashing/looping bug has been fixed.
-L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
-
-=item *
-
-UTF-8 variable names used in array indexes, unquoted UTF-8 HERE-document
-terminators and UTF-8 function names all now work correctly.
-L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
-
-=item *
-
-Repeated global pattern matches in scalar context on large tainted strings were
-exponentially slow depending on the current match position in the string.
-L<[perl #123202]|https://rt.perl.org/Ticket/Display.html?id=123202>
-
-=item *
-
-Various crashes due to the parser getting confused by syntax errors have been
-fixed.
-L<[perl #123801]|https://rt.perl.org/Ticket/Display.html?id=123801>
-L<[perl #123802]|https://rt.perl.org/Ticket/Display.html?id=123802>
-L<[perl #123955]|https://rt.perl.org/Ticket/Display.html?id=123955>
-L<[perl #123995]|https://rt.perl.org/Ticket/Display.html?id=123995>
-
-=item *
-
-C<split> in the scope of lexical C<$>_ has been fixed not to fail assertions.
-L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
-
-=item *
-
-C<my $x : attr> syntax inside various list operators no longer fails
-assertions.
-L<[perl #123817]|https://rt.perl.org/Ticket/Display.html?id=123817>
-
-=item *
-
-An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
-identifier) would cause the parser to crash, instead of simply trying the C<@> as
-literal. This has been fixed.
-L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
-
-=item *
-
-C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
-longer does.
-L<[perl #123847]|https://rt.perl.org/Ticket/Display.html?id=123847>
-
-=item *
-
-C<foreach> in scalar context was not pushing an item on to the stack, resulting
-in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.) It has
-been fixed to return C<undef>.
-L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
-
-=item *
-
-A memory leak introduced in Perl 5.21.6 has been fixed.
-L<[perl #123922]|https://rt.perl.org/Ticket/Display.html?id=123922>
-
-=item *
-
-A regression in the behaviour of the C<readline> built-in function, caused by
-the introduction of the C<< <<>> >> operator, has been fixed.
-L<[perl #123990]|https://rt.perl.org/Ticket/Display.html?id=123990>
-
-=item *
-
-Several cases of data used to store environment variable contents in core C
-code being potentially overwritten before being used have been fixed.
-L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
-
-=item *
-
-Patterns starting with C</.*/> are now fast again.
-L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
-
-=item *
-
-The original visible value of C<$/> is now preserved when it is set to
-an invalid value. Previously if you set C<$/> to a reference to an
-array, for example, perl would produce a runtime error and not set
-C<PL_rs>, but perl code that checked C<$/> would see the array
-reference.
-L<[perl #123218]|https://rt.perl.org/Ticket/Display.html?id=123218>.
-
-=item *
-
-In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
-be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
-warning is issued when something looking like a POSIX class is not
-inside a bracketed class. That warning wasn't getting generated when
-the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
-
-=item *
-
-Fix a couple of size calculation overflows.
-L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
-
-=item *
-
-A bug introduced in 5.21.6, C<dump LABEL> acted the same as C<goto
-LABEL>. This has been fixed.
-L<[perl #123836]|https://rt.perl.org/Ticket/Display.html?id=123836>.
-
-=item *
-
-Perl 5.14.0 introduced a bug whereby C<eval { LABEL: }> would crash. This
-has been fixed.
-L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
-
-=item *
-
-Various crashes due to the parser getting confused by syntax errors have
-been fixed.
-L<[perl #123617]|https://rt.perl.org/Ticket/Display.html?id=123617>.
-L<[perl #123737]|https://rt.perl.org/Ticket/Display.html?id=123737>.
-L<[perl #123753]|https://rt.perl.org/Ticket/Display.html?id=123753>.
-L<[perl #123677]|https://rt.perl.org/Ticket/Display.html?id=123677>.
-
-=item *
-
-Code like C</$a[/> used to read the next line of input and treat it as
-though it came immediately after the opening bracket. Some invalid code
-consequently would parse and run, but some code caused crashes, so this is
-now disallowed.
-L<[perl #123712]|https://rt.perl.org/Ticket/Display.html?id=123712>.
-
-=item *
-
-Fix argument underflow for C<pack>.
-L<[perl #123874]|https://rt.perl.org/Ticket/Display.html?id=123874>.
-
-=item *
-
-Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
-instead of faulting.
-
-=item *
-
-C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
-L<[perl #123816]|https://rt.perl.org/Ticket/Display.html?id=123816>.
-
-=item *
-
-The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
-
-=item *
-
-Fixed infinite loop in parsing backrefs in regexp patterns.
-
-=item *
-
-Several minor bug fixes in behavior of Inf and NaN, including
-warnings when stringifying Inf-like or NaN-like strings. For example,
-"NaNcy" doesn't numify to NaN anymore.
-
-=item *
-
-Only stringy classnames are now shared. This fixes some failures in L<autobox>.
-L<[perl #100819]|https://rt.cpan.org/Ticket/Display.html?id=100819>.
-
-=item *
-
-A bug in regular expression patterns that could lead to segfaults and
-other crashes has been fixed. This occurred only in patterns compiled
-with C<"/i">, while taking into account the current POSIX locale (this usually
-means they have to be compiled within the scope of C<S<"use locale">>),
-and there must be a string of at least 128 consecutive bytes to match.
-L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
-
-=item *
-
-C<s///> now works on very long strings instead of dying with 'Substitution
-loop'.
-L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
-L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
-
-=item *
-
-C<gmtime> no longer crashes with not-a-number values.
-L<[perl #123495]|https://rt.perl.org/Ticket/Display.html?id=123495>.
-
-=item *
-
-C<\()> (reference to an empty list) and C<y///> with lexical C<$_> in scope
-could do a bad write past the end of the stack. They have been fixed
-to extend the stack first.
-
-=item *
-
-C<prototype()> with no arguments used to read the previous item on the
-stack, so C<print "foo", prototype()> would print foo's prototype. It has
-been fixed to infer C<$_> instead.
-L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
-
-=item *
-
-Some cases of lexical state subs inside predeclared subs could crash but no
-longer do.
-
-=item *
-
-Some cases of nested lexical state subs inside anonymous subs could cause
-'Bizarre copy' errors or possibly even crash.
-
-=item *
-
-When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
-sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
-bug, which started to occur in Perl 5.18, has been fixed.
-L<[perl #123553]|https://rt.perl.org/Ticket/Display.html?id=123553>.
-
-=item *
-
-Certain syntax errors in substitutions, such as C<< s/${E<lt>E<gt>{})// >>, would
-crash, and had done so since Perl 5.10. (In some cases the crash did not
-start happening till 5.16.) The crash has, of course, been fixed.
-L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
-
-=item *
-
-A repeat expression like C<33 x ~3> could cause a large buffer
-overflow since the new output buffer size was not correctly handled by
-SvGROW(). An expression like this now properly produces a memory wrap
-panic.
-L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
-
-=item *
-
-C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
-pp_formline() didn't set the pointer used to mark the chop position,
-which led to the C<FF_MORE> case crashing with a segmentation fault.
-This has been fixed.
-L<[perl #123538]|https://rt.perl.org/Ticket/Display.html?id=123538>.
-
-=item *
-
-A possible buffer overrun and crash when parsing a literal pattern during
-regular expression compilation has been fixed.
-L<[perl #123604]|https://rt.perl.org/Ticket/Display.html?id=123604>.
-
-=item *
-
-C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
-passed a closed file handle.
-L<[perl #122703]|https://rt.perl.org/Ticket/Display.html?id=122703>.
-
-=item *
-
-op_free() no longer crashes due to a stack overflow when freeing a
-deeply recursive op tree.
-L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
-
-=item *
-
-scalarvoid() would crash due to a stack overflow when processing a
-deeply recursive op tree.
-L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
-
-=item *
-
-In Perl 5.20.0, C<$^N> accidentally had the internal UTF8 flag turned off
-if accessed from a code block within a regular expression, effectively
-UTF8-encoding the value. This has been fixed.
-L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
-
-=item *
-
-A failed C<semctl> call no longer overwrites existing items on the stack,
-causing C<(semctl(-1,0,0,0))[0]> to give an "uninitialized" warning.
-
-=item *
-
-C<else{foo()}> with no space before C<foo> is now better at assigning the
-right line number to that statement.
-L<[perl #122695]|https://rt.perl.org/Ticket/Display.html?id=122695>.
-
-=item *
-
-Sometimes the assignment in C<@array = split> gets optimised and C<split>
-itself writes directly to the array. This caused a bug, preventing this
-assignment from being used in lvalue context. So
-C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
-Perl 3, when the optimisation was added.) This optimisation, and the bug,
-started to happen in more cases in 5.21.5. It has now been fixed.
-L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
-
-=item *
-
-When argument lists that fail the checks installed by subroutine
-signatures, the resulting error messages now give the file and line number
-of the caller, not of the called subroutine.
-L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
-
-=item *
-
-Flip-flop operators (C<..> and C<...> in scalar context) used to maintain
-a separate state for each recursion level (the number of times the
-enclosing sub was called recursively), contrary to the documentation. Now
-each closure has one internal state for each flip-flop.
-L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
-
-=item *
-
-C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
-permitted as the first thing in a C<map> or C<grep> block, the block after
-C<print> or C<say> (or other functions) returning a handle, and within
-C<${...}>, C<@{...}>, etc.
-L<[perl #122782]|https://rt.perl.org/Ticket/Display.html?id=122782>.
-
-=item *
-
-The repetition operator C<x> now propagates lvalue context to its left-hand
-argument when used in contexts like C<foreach>. That allows
-S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
-$_.
-
-=item *
-
-C<(...) x ...> in scalar context used to corrupt the stack if one operand
-were an object with "x" overloading, causing erratic behaviour.
-L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
-
-=item *
-
-Assignment to a lexical scalar is often optimised away (as mentioned under
-L</Performance Enhancements>). Various bugs related to this optimisation
-have been fixed. Certain operators on the right-hand side would sometimes
-fail to assign the value at all or assign the wrong value, or would call
-STORE twice or not at all on tied variables. The operators affected were
-C<$foo++>, C<$foo-->, and C<-$foo> under C<use integer>, C<chomp>, C<chr>
-and C<setpgrp>.
-
-=item *
-
-List assignments were sometimes buggy if the same scalar ended up on both
-sides of the assignment due to used of C<tied>, C<values> or C<each>. The
-result would be the wrong value getting assigned.
-
-=item *
-
-C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
-to mean C<setpgrp(0)>. This has been fixed.
-
-=item *
-
-C<__SUB__> could return the wrong value or even corrupt memory under the
-debugger (the C<-d> switch) and in subs containing C<eval $string>.
-
-=item *
-
-When S<C<sub () { $var }>> becomes inlinable, it now returns a different
-scalar each time, just as a non-inlinable sub would, though Perl still
-optimises the copy away in cases where it would make no observable
-difference.
-
-=item *
-
-S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
-eligible for inlining. The former would crash; the latter would just
-throw the attributes away. An exception is made for the little-known
-":method" attribute, which does nothing much.
-
-=item *
-
-Inlining of subs with an empty prototype is now more consistent than
-before. Previously, a sub with multiple statements, all but the last
-optimised away, would be inlinable only if it were an anonymous sub
-containing a string C<eval> or C<state> declaration or closing over an
-outer lexical variable (or any anonymous sub under the debugger). Now any
-sub that gets folded to a single constant after statements have been
-optimised away is eligible for inlining. This applies to things like C<sub
-() { jabber() if DEBUG; 42 }>.
-
-Some subroutines with an explicit C<return> were being made inlinable,
-contrary to the documentation, Now C<return> always prevents inlining.
-
-=item *
-
-On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
-scalar assigned to had contained a UTF8 string previously, then C<crypt>
-would not turn off the UTF8 flag, thus corrupting the return value. This
-would happen with C<$lexical = crypt ...>.
-
-=item *
-
-C<crypt> no longer calls C<FETCH> twice on a tied first argument.
-
-=item *
-
-An unterminated here-doc on the last line of a quote-like operator
-(C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
-started doing so in 5.18.
-
-=item *
-
-Fixed two assertion failures introduced into C<-DPERL_OP_PARENT>
-builds.
-L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
-
-=item *
-
-C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
-size.
-L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
-
-=item *
-
-A small previously intentional memory leak in PERL_SYS_INIT/PERL_SYS_INIT3 on
-Win32 builds was fixed. This might affect embedders who repeatedly create and
-destroy perl engines within the same process.
-
-=item *
-
-C<POSIX::localeconv()> now returns the data for the program's underlying
-locale even when called from outside the scope of S<C<use locale>>.
-
-=item *
-
-C<POSIX::localeconv()> now works properly on platforms which don't have
-C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
-to disregard either or both of these locale categories. In such
-circumstances, there are now no entries for the corresponding values in
-the hash returned by C<localeconv()>.
-
-=item *
-
-C<POSIX::localeconv()> now marks appropriately the values it returns as
-UTF-8 or not. Previously they were always returned as bytes, even if
-they were supposed to be encoded as UTF-8.
-
-=item *
-
-On Microsoft Windows, within the scope of C<S<use locale>>, the following
-POSIX character classes gave results for many locales that did not
-conform to the POSIX standard:
-C<[[:alnum:]]>,
-C<[[:alpha:]]>,
-C<[[:blank:]]>,
-C<[[:digit:]]>,
-C<[[:graph:]]>,
-C<[[:lower:]]>,
-C<[[:print:]]>,
-C<[[:punct:]]>,
-C<[[:upper:]]>,
-C<[[:word:]]>,
-and
-C<[[:xdigit:]]>.
-These are because the underlying Microsoft implementation does not
-follow the standard. Perl now takes special precautions to correct for
-this.
-
-=item *
-
-Many issues have been detected by L<Coverity|http://www.coverity.com/> and
-fixed.
-
-=item *
-
-system() and friends should now work properly on more Android builds.
-
-Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
-would end up being ignored by some of the build process. This caused perls
-cross-compiled for Android to end up with defective versions of C<system()>,
-exec() and backticks: the commands would end up looking for C</bin/sh>
-instead of C</system/bin/sh>, and so would fail for the vast majority
-of devices, leaving C<$!> as C<ENOENT>.
-
-=item *
-
-C<qr(...\(...\)...)>,
-C<qr[...\[...\]...]>,
-and
-C<qr{...\{...\}...}>
-now work. Previously it was impossible to escape these three
-left-characters with a backslash within a regular expression pattern
-where otherwise they would be considered metacharacters, and the pattern
-opening delimiter was the character, and the closing delimiter was its
-mirror character.
-
-=item *
-
-C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
-introduced in 5.20, is now fixed.
-L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
-
-=item *
-
-A non-word boundary in a regular expression (C<< \B >>) did not always
-match the end of the string; in particular C<< q{} =~ /\B/ >> did not
-match. This bug, introduced in perl 5.14, is now fixed.
-L<[perl #122090]|https://rt.perl.org/Ticket/Display.html?id=122090>.
-
-=item *
-
-C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
-L<[perl #122171]|https://rt.perl.org/Ticket/Display.html?id=122171>.
-
-=item *
-
-Failing to compile C<use Foo> in an eval could leave a spurious
-C<BEGIN> subroutine definition, which would produce a "Subroutine
-BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
-block.
-L<[perl #122107]|https://rt.perl.org/Ticket/Display.html?id=122107>.
-
-=item *
-
-C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
-begin with an opening brace.
-L<[perl #46947]|https://rt.perl.org/Ticket/Display.html?id=46947>.
-
-=item *
-
-External libraries and Perl may have different ideas of what the locale is.
-This is problematic when parsing version strings if the locale's numeric
-separator has been changed. Version parsing has been patched to ensure
-it handles the locales correctly.
-L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>.
-
-=item *
-
-A bug has been fixed where zero-length assertions and code blocks inside of a
-regex could cause C<pos> to see an incorrect value.
-L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>.
-
-=item *
-
-Constant dereferencing now works correctly for typeglob constants. Previously
-the glob was stringified and its name looked up. Now the glob itself is used.
-L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
-
-=item *
-
-When parsing a funny character (C<$> C<@> C<%> C<&)> followed by braces,
-the parser no
-longer tries to guess whether it is a block or a hash constructor (causing a
-syntax error when it guesses the latter), since it can only be a block.
-
-=item *
-
-S<C<undef $reference>> now frees the referent immediately, instead of hanging on
-to it until the next statement.
-L<[perl #122556]|https://rt.perl.org/Ticket/Display.html?id=122556>
-
-=item *
-
-Various cases where the name of a sub is used (autoload, overloading, error
-messages) used to crash for lexical subs, but have been fixed.
-
-=item *
-
-Bareword lookup now tries to avoid vivifying packages if it turns out the
-bareword is not going to be a subroutine name.
-
-=item *
-
-Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer deletes
-any subroutine named C<__ANON__> in the current package. Not only was
-C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
-back to Perl 5.8.0.
-
-=item *
-
-Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
-of the same name declared by C<use constant>. This bug was introduced in Perl
-5.10.0.
-
-=item *
-
-Under some conditions a warning raised in compilation of regular expression
-patterns could be displayed multiple times. This is now fixed.
-
-=item *
-
-C<qr/[\N{named sequence}]/> now works properly in many instances. Some names
-known to C<\N{...}> refer to a sequence of multiple characters, instead of the
-usual single character. Bracketed character classes generally only match
-single characters, but now special handling has been added so that they can
-match named sequences, but not if the class is inverted or the sequence is
-specified as the beginning or end of a range. In these cases, the only
-behavior change from before is a slight rewording of the fatal error message
-given when this class is part of a C<?[...])> construct. When the C<[...]>
-stands alone, the same non-fatal warning as before is raised, and only the
-first character in the sequence is used, again just as before.
-
-=item *
-
-Tainted constants evaluated at compile time no longer cause unrelated
-statements to become tainted.
-L<[perl #122669]|https://rt.perl.org/Ticket/Display.html?id=122669>
-
-=item *
-
-S<C<open $$fh, ...>>, which vivifies a handle with a name like C<"main::_GEN_0">, was
-not giving the handle the right reference count, so a double free could happen.
-
-=item *
-
-When deciding that a bareword was a method name, the parser would get confused
-if an C<our> sub with the same name existed, and look up the method in the
-package of the C<our> sub, instead of the package of the invocant.
-
-=item *
-
-The parser no longer gets confused by C<\U=> within a double-quoted string. It
-used to produce a syntax error, but now compiles it correctly.
-L<[perl #80368]|https://rt.perl.org/Ticket/Display.html?id=80368>
-
-=item *
-
-It has always been the intention for the C<-B> and C<-T> file test operators to
-treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
-been updated to say this.) Previously, it was possible for some files to be
-considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
-operators now work on EBCDIC platforms as well.
-
-=item *
-
-Under some conditions warning messages raised during regular expression pattern
-compilation were being output more than once. This has now been fixed.
-
-=item *
-
-A regression has been fixed that was introduced in Perl 5.20.0 (fixed in Perl
-5.20.1 as well as here) in which a UTF-8 encoded regular expression pattern
-that contains a single ASCII lowercase letter does not match its uppercase
-counterpart.
-L<[perl #122655]|https://rt.perl.org/Ticket/Display.html?id=122655>
-
-=item *
-
-Constant folding could incorrectly suppress warnings if lexical warnings (C<use
-warnings> or C<no warnings>) were not in effect and C<$^W> were false at
-compile time and true at run time.
-
-=item *
-
-Loading UTF8 tables during a regular expression match could cause assertion
-failures under debugging builds if the previous match used the very same
-regular expression.
-L<[perl #122747]|https://rt.perl.org/Ticket/Display.html?id=122747>
-
-=item *
-
-Thread cloning used to work incorrectly for lexical subs, possibly causing
-crashes or double frees on exit.
-
-=item *
-
-Since Perl 5.14.0, deleting C<$SomePackage::{__ANON__}> and then undefining an
-anonymous subroutine could corrupt things internally, resulting in
-L<Devel::Peek> crashing or L<B.pm|B> giving nonsensical data. This has been
-fixed.
-
-=item *
-
-S<C<(caller $n)[3]>> now reports names of lexical subs, instead of treating them
-as C<"(unknown)">.
-
-=item *
-
-C<sort subname LIST> now supports lexical subs for the comparison routine.
-
-=item *
-
-Aliasing (e.g., via C<*x = *y>) could confuse list assignments that mention the
-two names for the same variable on either side, causing wrong values to be
-assigned.
-L<[perl #15667]|https://rt.perl.org/Ticket/Display.html?id=15667>
-
-=item *
-
-Long here-doc terminators could cause a bad read on short lines of input. This
-has been fixed. It is doubtful that any crash could have occurred. This bug
-goes back to when here-docs were introduced in Perl 3.000 twenty-five years
-ago.
-
-=item *
-
-An optimization in C<split> to treat C<split/^/> like C<split/^/m> had the
-unfortunate side-effect of also treating C<split/\A/> like C<split/^/m>, which
-it should not. This has been fixed. (Note, however, that C<split/^x/> does
-not behave like C<split/^x/m>, which is also considered to be a bug and will be
-fixed in a future version.)
-L<[perl #122761]|https://rt.perl.org/Ticket/Display.html?id=122761>
-
-=item *
-
-The little-known S<C<my Class $var>> syntax (see L<fields> and L<attributes>)
-could get confused in the scope of C<use utf8> if C<Class> were a constant
-whose value contained Latin-1 characters.
-
-=item *
-
-Locking and unlocking values via L<Hash::Util> or C<Internals::SvREADONLY>
-no longer has any effect on values that are read-only to begin.
-Previously, unlocking such values could result in crashes, hangs or
-other erratic behaviour.
-
-=item *
-
-The internal C<looks_like_number> function (which L<Scalar::Util> provides
-access to) began erroneously to return true for "-e1" in 5.21.4, affecting
-also C<-'-e1'>. This has been fixed.
-
-=item *
-
-The flip-flop operator (C<..> in scalar context) would return the same
-scalar each time, unless the containing subroutine was called recursively.
-Now it always returns a new scalar.
-L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
-
-=item *
-
-Some unterminated C<(?(...)...)> constructs in regular expressions would
-either crash or give erroneous error messages. C</(?(1)/> is one such
-example.
-
-=item *
-
-S<C<pack "w", $tied>> no longer calls FETCH twice.
-
-=item *
-
-List assignments like S<C<($x, $z) = (1, $y)>> now work correctly if C<$x> and
-C<$y> have been aliased by C<foreach>.
-
-=item *
-
-Some patterns including code blocks with syntax errors, such as
-C</ (?{(^{})/>, would hang or fail assertions on debugging builds. Now
-they produce errors.
-
-=item *
-
-An assertion failure when parsing C<sort> with debugging enabled has been
-fixed.
-L<[perl #122771]|https://rt.perl.org/Ticket/Display.html?id=122771>.
-
-=item *
-
-S<C<*a = *b; @a = split //, $b[1]>> could do a bad read and produce junk
-results.
-
-=item *
-
-In S<C<() = @array = split>>, the S<C<() =>> at the beginning no longer confuses
-the optimizer, making it assume a limit of 1.
-
-=item *
-
-Fatal warnings no longer prevent the output of syntax errors.
-L<[perl #122966]|https://rt.perl.org/Ticket/Display.html?id=122966>.
-
-=item *
-
-Fixed a NaN double to long double conversion error on VMS. For quiet NaNs
-(and only on Itanium, not Alpha) negative infinity instead of NaN was
-produced.
-
-=item *
-
-Fixed the issue that caused C<< make distclean >> to leave files behind
-that shouldn't.
-L<[perl #122820]|https://rt.perl.org/Ticket/Display.html?id=122820>.
-
-=item *
-
-AIX now sets the length in C<< getsockopt >> correctly.
-L<[perl #120835]|https://rt.perl.org/Ticket/Display.html?id=120835>.
-L<[cpan #91183]|https://rt.cpan.org/Ticket/Display.html?id=91183>.
-L<[cpan #85570]|https://rt.cpan.org/Ticket/Display.html?id=85570>.
-
-=item *
-
-During the pattern optimization phase, we no longer recurse into
-C<GOSUB>/C<GOSTART> when not C<SCF_DO_SUBSTR>. This prevents the optimizer
-to run "forever" and exhaust all memory.
-L<[perl #122283]|https://rt.perl.org/Ticket/Display.html?id=122283>.
-
-=item *
-
-F<< t/op/crypt.t >> now performs SHA-256 algorithm if the default one
-is disabled.
-L<[perl #121591]|https://rt.perl.org/Ticket/Display.html?id=121591>.
-
-=item *
-
-Fixed an off-by-one error when setting the size of shared array.
-L<[perl #122950]|https://rt.perl.org/Ticket/Display.html?id=122950>.
-
-=item *
-
-Fixed a bug that could cause perl to execute an infinite loop during
-compilation.
-L<[perl #122995]|https://rt.perl.org/Ticket/Display.html?id=122995>.
-
-=item *
-
-On Win32, restoring in a child pseudo-process a variable that was
-C<local()>ed in a parent pseudo-process before the C<fork> happened caused
-memory corruption and a crash in the child pseudo-process (and therefore OS
-process).
-L<[perl #40565]|https://rt.perl.org/Ticket/Display.html?id=40565>.
-
-=item *
-
-Calling C<write> on a format with a C<^**> field could produce a panic
-in C<sv_chop()> if there were insufficient arguments or if the variable
-used to fill the field was empty.
-L<[perl #123245]|https://rt.perl.org/Ticket/Display.html?id=123245>.
-
-=item *
-
-Non-ASCII lexical sub names (use in error messages) on longer have extra
-junk on the end.
-
-=item *
-
-The C<\@> subroutine prototype no longer flattens parenthesized arrays
-(taking a reference to each element), but takes a reference to the array
-itself.
-L<[perl #47363]|https://rt.perl.org/Ticket/Display.html?id=47363>.
-
-=item *
-
-A block containing nothing except a C-style C<for> loop could corrupt the
-stack, causing lists outside the block to lose elements or have elements
-overwritten. This could happen with C<map { for(...){...} } ...> and with
-lists containing C<do { for(...){...} }>.
-L<[perl #123286]|https://rt.perl.org/Ticket/Display.html?id=123286>.
-
-=item *
-
-C<scalar()> now propagates lvalue context, so that
-S<C<for(scalar($#foo)) { ... }>> can modify C<$#foo> through C<$_>.
-
-=item *
-
-C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
-L<[perl #123344]|https://rt.perl.org/Ticket/Display.html?id=123344>.
-
-=item *
-
-S<C<eval '$variable'>> in nested named subroutines would sometimes look up a
-global variable even with a lexical variable in scope.
-
-=item *
-
-In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
-keyword started chopping of the last 6 characters and treating the result
-as a sort sub name. The previous behaviour of treating "CORE::fake" as a
-sort sub name has been restored.
-L<[perl #123410]|https://rt.perl.org/Ticket/Display.html?id=123410>.
-
-=item *
-
-Outside of C<use utf8>, a single-character Latin-1 lexical variable is
-disallowed. The error message for it, "Can't use global C<$foo>...", was
-giving garbage instead of the variable name.
-
-=item *
-
-C<readline> on a nonexistent handle was causing C<${^LAST_FH}> to produce a
-reference to an undefined scalar (or fail an assertion). Now
-C<${^LAST_FH}> ends up undefined.
-
-=item *
-
-C<(...)x...> in void context now applies scalar context to the left-hand
-argument, instead of the context the current sub was called in.
-L<[perl #123020]|https://rt.perl.org/Ticket/Display.html?id=123020>.
-
-=back
-
-=head1 Known Problems
-
-=over 4
-
-=item *
-
-A goal is for Perl to be able to be recompiled to work reasonably well on any
-Unicode version. In Perl 5.22, though, the earliest such version is Unicode
-5.1 (current is 7.0).
-
-=item *
-
-EBCDIC platforms
-
-=over 4
-
-=item *
-
-The C<cmp> (and hence C<sort>) operators do not necessarily give the
-correct results when both operands are UTF-EBCDIC encoded strings and
-there is a mixture of ASCII and/or control characters, along with other
-characters.
-
-=item *
-
-Ranges containing C<\N{...}> in the C<tr///> (and C<y///>)
-transliteration operators are treated differently than the equivalent
-ranges in regular expression pattersn. They should, but don't, cause
-the values in the ranges to all be treated as Unicode code points, and
-not native ones. (L<perlre/Version 8 Regular Expressions> gives
-details as to how it should work.)
-
-=item *
-
-Encode and encoding are mostly broken.
-
-=item *
-
-Many CPAN modules that are shipped with core show failing tests.
-
-=item *
-
-C<pack>/C<unpack> with C<"U0"> format may not work properly.
-
-=back
-
-=item *
-
-The following modules are known to have test failures with this version of
-Perl. Patches have been submitted, so there will hopefully be new releases
-soon:
-
-=over
-
-=item *
-
-L<B::Generate> version 1.50
-
-=item *
-
-L<B::Utils> version 0.25
-
-=item *
-
-L<Dancer> version 1.3130
-
-=item *
-
-L<Data::Alias> version 1.18
-
-=item *
-
-L<Data::Util> version 0.63
-
-=item *
-
-L<Devel::Spy> version 0.07
-
-=item *
-
-L<Lexical::Var> version 0.009
-
-=item *
-
-L<Mason> version 2.22
-
-=item *
-
-L<Padre> version 1.00
-
-=item *
-
-L<Parse::Keyword> 0.08
-
-=back
-
-=back
+XXX If any significant core contributor has died, we've added a short obituary
+here.
=head1 Acknowledgements
XXX Generate this with:
- perl Porting/acknowledgements.pl v5.20.0..HEAD
+ perl Porting/acknowledgements.pl v5.23.1..HEAD
=head1 Reporting Bugs
If you find what you think is a bug, you might check the articles recently
posted to the comp.lang.perl.misc newsgroup and the perl bug database at
-https://rt.perl.org/ . There may also be information at
-http://www.perl.org/ , the Perl Home Page.
+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
https://perl5.git.perl.org / perl5.git / blobdiff