5 perl5220delta - what is new for perl v5.22.0
9 This document describes differences between the 5.20.0 release and the 5.22.0
12 If you are upgrading from an earlier release such as 5.18.0, first read
13 L<perl5200delta>, which describes differences between 5.18.0 and 5.20.0.
15 =head1 Core Enhancements
17 =head2 New bitwise operators
19 A new experimental facility has been added that makes the four standard
20 bitwise operators (C<& | ^ ~>) treat their operands consistently as
21 numbers, and introduces four new dotted operators (C<&. |. ^. ~.>) that
22 treat their operands consistently as strings. The same applies to the
23 assignment variants (C<&= |= ^= &.= |.= ^.=>).
25 To use this, enable the "bitwise" feature and disable the
26 "experimental::bitwise" warnings category. See L<perlop/Bitwise String
27 Operators> for details.
28 L<[GH #14348]|https://github.com/Perl/perl5/issues/14348>.
30 =head2 New double-diamond operator
32 C<<< <<>> >>> is like C<< <> >> but uses three-argument C<open> to open
33 each file in C<@ARGV>. This means that each element of C<@ARGV> will be treated
34 as an actual file name, and C<"|foo"> won't be treated as a pipe open.
36 =head2 New C<\b> boundaries in regular expressions
40 C<gcb> stands for Grapheme Cluster Boundary. It is a Unicode property
41 that finds the boundary between sequences of characters that look like a
42 single character to a native speaker of a language. Perl has long had
43 the ability to deal with these through the C<\X> regular escape
44 sequence. Now, there is an alternative way of handling these. See
45 L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
49 C<wb> stands for Word Boundary. It is a Unicode property
50 that finds the boundary between words. This is similar to the plain
51 C<\b> (without braces) but is more suitable for natural language
52 processing. It knows, for example, that apostrophes can occur in the
53 middle of words. See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
57 C<sb> stands for Sentence Boundary. It is a Unicode property
58 to aid in parsing natural language sentences.
59 See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
61 =head2 Non-Capturing Regular Expression Flag
63 Regular expressions now support a C</n> flag that disables capturing
64 and filling in C<$1>, C<$2>, etc inside of groups:
66 "hello" =~ /(hi|hello)/n; # $1 is not set
68 This is equivalent to putting C<?:> at the beginning of every capturing group.
70 See L<perlre/"n"> for more information.
72 =head2 C<use re 'strict'>
74 This applies stricter syntax rules to regular expression patterns
75 compiled within its scope. This will hopefully alert you to typos and
76 other unintentional behavior that backwards-compatibility issues prevent
77 us from reporting in normal regular expression compilations. Because the
78 behavior of this is subject to change in future Perl releases as we gain
79 experience, using this pragma will raise a warning of category
80 C<experimental::re_strict>.
81 See L<'strict' in re|re/'strict' mode>.
83 =head2 Unicode 7.0 (with correction) is now supported
85 For details on what is in this release, see
86 L<http://www.unicode.org/versions/Unicode7.0.0/>.
87 The version of Unicode 7.0 that comes with Perl includes
88 a correction dealing with glyph shaping in Arabic
89 (see L<http://www.unicode.org/errata/#current_errata>).
92 =head2 S<C<use locale>> can restrict which locale categories are affected
94 It is now possible to pass a parameter to S<C<use locale>> to specify
95 a subset of locale categories to be locale-aware, with the remaining
96 ones unaffected. See L<perllocale/The "use locale" pragma> for details.
98 =head2 Perl now supports POSIX 2008 locale currency additions
100 On platforms that are able to handle POSIX.1-2008, the
102 L<C<POSIX::localeconv()>|perllocale/The localeconv function>
103 includes the international currency fields added by that version of the
104 POSIX standard. These are
105 C<int_n_cs_precedes>,
106 C<int_n_sep_by_space>,
108 C<int_p_cs_precedes>,
109 C<int_p_sep_by_space>,
113 =head2 Better heuristics on older platforms for determining locale UTF-8ness
115 On platforms that implement neither the C99 standard nor the POSIX 2001
116 standard, determining if the current locale is UTF-8 or not depends on
117 heuristics. These are improved in this release.
119 =head2 Aliasing via reference
121 Variables and subroutines can now be aliased by assigning to a reference:
126 Aliasing can also be accomplished
127 by using a backslash before a C<foreach> iterator variable; this is
128 perhaps the most useful idiom this feature provides:
130 foreach \%hash (@array_of_hash_refs) { ... }
132 This feature is experimental and must be enabled via S<C<use feature
133 'refaliasing'>>. It will warn unless the C<experimental::refaliasing>
134 warnings category is disabled.
136 See L<perlref/Assigning to References>
138 =head2 C<prototype> with no arguments
140 C<prototype()> with no arguments now infers C<$_>.
141 L<[GH #14376]|https://github.com/Perl/perl5/issues/14376>.
143 =head2 New C<:const> subroutine attribute
145 The C<const> attribute can be applied to an anonymous subroutine. It
146 causes the new sub to be executed immediately whenever one is created
147 (I<i.e.> when the C<sub> expression is evaluated). Its value is captured
148 and used to create a new constant subroutine that is returned. This
149 feature is experimental. See L<perlsub/Constant Functions>.
151 =head2 C<fileno> now works on directory handles
153 When the relevant support is available in the operating system, the
154 C<fileno> builtin now works on directory handles, yielding the
155 underlying file descriptor in the same way as for filehandles. On
156 operating systems without such support, C<fileno> on a directory handle
157 continues to return the undefined value, as before, but also sets C<$!> to
158 indicate that the operation is not supported.
160 Currently, this uses either a C<dd_fd> member in the OS C<DIR>
161 structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
163 =head2 List form of pipe open implemented for Win32
165 The list form of pipe:
167 open my $fh, "-|", "program", @arguments;
169 is now implemented on Win32. It has the same limitations as C<system
170 LIST> on Win32, since the Win32 API doesn't accept program arguments
173 =head2 Assignment to list repetition
175 C<(...) x ...> can now be used within a list that is assigned to, as long
176 as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
177 = that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
179 =head2 Infinity and NaN (not-a-number) handling improved
181 Floating point values are able to hold the special values infinity, negative
182 infinity, and NaN (not-a-number). Now we more robustly recognize and
183 propagate the value in computations, and on output normalize them to the strings
184 C<Inf>, C<-Inf>, and C<NaN>.
186 See also the L<POSIX> enhancements.
188 =head2 Floating point parsing has been improved
190 Parsing and printing of floating point values has been improved.
192 As a completely new feature, hexadecimal floating point literals
193 (like C<0x1.23p-4>) are now supported, and they can be output with
194 S<C<printf "%a">>. See L<perldata/Scalar value constructors> for more
197 =head2 Packing infinity or not-a-number into a character is now fatal
199 Before, when trying to pack infinity or not-a-number into a
200 (signed) character, Perl would warn, and assumed you tried to
201 pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
202 C<< U+FFFD >> was returned.
204 But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
205 result in a fatal error.
207 =head2 Experimental C Backtrace API
209 Perl now supports (via a C level API) retrieving
210 the C level backtrace (similar to what symbolic debuggers like gdb do).
212 The backtrace returns the stack trace of the C call frames,
213 with the symbol names (function names), the object names (like "perl"),
214 and if it can, also the source code locations (file:line).
216 The supported platforms are Linux and OS X (some *BSD might work at
217 least partly, but they have not yet been tested).
219 The feature needs to be enabled with C<Configure -Dusecbacktrace>.
221 See L<perlhacktips/"C backtrace"> for more information.
225 =head2 Perl is now compiled with C<-fstack-protector-strong> if available
227 Perl has been compiled with the anti-stack-smashing option
228 C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
229 called C<-fstack-protector-strong>, if available.
231 =head2 The L<Safe> module could allow outside packages to be replaced
233 Critical bugfix: outside packages could be replaced. L<Safe> has
234 been patched to 2.38 to address this.
236 =head2 Perl is now always compiled with C<-D_FORTIFY_SOURCE=2> if available
238 The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
239 gcc 4.*, is now always used for compiling Perl, if available.
241 Note that this isn't necessarily a huge step since in many platforms
242 the step had already been taken several years ago: many Linux
243 distributions (like Fedora) have been using this option for Perl,
244 and OS X has enforced the same for many years.
246 =head1 Incompatible Changes
248 =head2 Subroutine signatures moved before attributes
250 The experimental sub signatures feature, as introduced in 5.20, parsed
251 signatures after attributes. In this release, following feedback from users
252 of the experimental feature, the positioning has been moved such that
253 signatures occur after the subroutine name (if any) and before the attribute
256 =head2 C<&> and C<\&> prototypes accepts only subs
258 The C<&> prototype character now accepts only anonymous subs (C<sub
259 {...}>), things beginning with C<\&>, or an explicit C<undef>. Formerly
260 it erroneously also allowed references to arrays, hashes, and lists.
261 L<[GH #2776]|https://github.com/Perl/perl5/issues/2776>.
262 L<[GH #14186]|https://github.com/Perl/perl5/issues/14186>.
263 L<[GH #14353]|https://github.com/Perl/perl5/issues/14353>.
265 In addition, the C<\&> prototype was allowing subroutine calls, whereas
266 now it only allows subroutines: C<&foo> is still permitted as an argument,
267 while C<&foo()> and C<foo()> no longer are.
268 L<[GH #10633]|https://github.com/Perl/perl5/issues/10633>.
270 =head2 C<use encoding> is now lexical
272 The L<encoding> pragma's effect is now limited to lexical scope. This
273 pragma is deprecated, but in the meantime, it could adversely affect
274 unrelated modules that are included in the same program; this change
277 =head2 List slices returning empty lists
279 List slices now return an empty list only if the original list was empty
280 (or if there are no indices). Formerly, a list slice would return an empty
281 list if all indices fell outside the original list; now it returns a list
282 of C<undef> values in that case.
283 L<[GH #12335]|https://github.com/Perl/perl5/issues/12335>.
285 =head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
287 E.g. S<C<\N{TOOE<nbsp>E<nbsp>MANY SPACES}>> or S<C<\N{TRAILING SPACE }>>.
288 This has been deprecated since v5.18.
290 =head2 S<C<use UNIVERSAL '...'>> is now a fatal error
292 Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
293 is now a fatal error. S<C<use UNIVERSAL>> without any arguments is still
296 =head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
298 In prior releases, failure to do this raised a deprecation warning.
300 =head2 Splitting the tokens C<(?> and C<(*> in regular expressions is now a fatal compilation error
302 These had been deprecated since v5.18.
304 =head2 C<qr/foo/x> now ignores all Unicode pattern white space
306 The C</x> regular expression modifier allows the pattern to contain
307 white space and comments (both of which are ignored) for improved
308 readability. Until now, not all the white space characters that Unicode
309 designates for this purpose were handled. The additional ones now
313 U+200E LEFT-TO-RIGHT MARK
314 U+200F RIGHT-TO-LEFT MARK
315 U+2028 LINE SEPARATOR
316 U+2029 PARAGRAPH SEPARATOR
318 The use of these characters with C</x> outside bracketed character
319 classes and when not preceded by a backslash has raised a deprecation
320 warning since v5.18. Now they will be ignored.
322 =head2 Comment lines within S<C<(?[ ])>> are now ended only by a C<\n>
324 S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
325 as if C</x> is always enabled. But there was a difference: comment
326 lines (following a C<#> character) were terminated by anything matching
327 C<\R> which includes all vertical whitespace, such as form feeds. For
328 consistency, this is now changed to match what terminates comment lines
329 outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
330 same as what terminates a heredoc string and formats.
332 =head2 C<(?[...])> operators now follow standard Perl precedence
334 This experimental feature allows set operations in regular expression patterns.
335 Prior to this, the intersection operator had the same precedence as the other
336 binary operators. Now it has higher precedence. This could lead to different
337 outcomes than existing code expects (though the documentation has always noted
338 that this change might happen, recommending fully parenthesizing the
339 expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
341 =head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
343 Really old Perl let you omit the C<@> on array names and the C<%> on hash
344 names in some spots. This has issued a deprecation warning since Perl
345 5.000, and is no longer permitted.
347 =head2 C<"$!"> text is now in English outside the scope of C<use locale>
349 Previously, the text, unlike almost everything else, always came out
350 based on the current underlying locale of the program. (Also affected
351 on some systems is C<"$^E">.) For programs that are unprepared to
352 handle locale differences, this can cause garbage text to be displayed.
353 It's better to display text that is translatable via some tool than
354 garbage text which is much harder to figure out.
356 =head2 C<"$!"> text will be returned in UTF-8 when appropriate
358 The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
359 when the text is actually non-ASCII UTF-8. This will enable programs
360 that are set up to be locale-aware to properly output messages in the
361 user's native language. Code that needs to continue the 5.20 and
362 earlier behavior can do the stringification within the scopes of both
363 S<C<use bytes>> and S<C<use locale ":messages">>. Within these two
364 scopes, no other Perl operations will
365 be affected by locale; only C<$!> and C<$^E> stringification. The
366 C<bytes> pragma causes the UTF-8 flag to not be set, just as in previous
367 Perl releases. This resolves
368 L<[GH #12035]|https://github.com/Perl/perl5/issues/12035>.
370 =head2 Support for C<?PATTERN?> without explicit operator has been removed
372 The C<m?PATTERN?> construct, which allows matching a regex only once,
373 previously had an alternative form that was written directly with a question
374 mark delimiter, omitting the explicit C<m> operator. This usage has produced
375 a deprecation warning since 5.14.0. It is now a syntax error, so that the
376 question mark can be available for use in new operators.
378 =head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
380 These have been deprecated since v5.6.1 and have raised deprecation
381 warnings since v5.16.
383 =head2 Using a hash or an array as a reference are now fatal errors
385 For example, C<< %foo->{"bar"} >> now causes a fatal compilation
386 error. These have been deprecated since before v5.8, and have raised
387 deprecation warnings since then.
389 =head2 Changes to the C<*> prototype
391 The C<*> character in a subroutine's prototype used to allow barewords to take
392 precedence over most, but not all, subroutine names. It was never
393 consistent and exhibited buggy behavior.
395 Now it has been changed, so subroutines always take precedence over barewords,
396 which brings it into conformity with similarly prototyped built-in functions:
400 splat(foo); # now always splat(foo())
401 splat(bar); # still splat('bar') as before
402 close(foo); # close(foo())
403 close(bar); # close('bar')
407 =head2 Setting C<${^ENCODING}> to anything but C<undef>
409 This variable allows Perl scripts to be written in an encoding other than
410 ASCII or UTF-8. However, it affects all modules globally, leading
411 to wrong answers and segmentation faults. New scripts should be written
412 in UTF-8; old scripts should be converted to UTF-8, which is easily done
413 with the L<piconv> utility.
415 =head2 Use of non-graphic characters in single-character variable names
417 The syntax for single-character variable names is more lenient than
418 for longer variable names, allowing the one-character name to be a
419 punctuation character or even invisible (a non-graphic). Perl v5.20
420 deprecated the ASCII-range controls as such a name. Now, all
421 non-graphic characters that formerly were allowed are deprecated.
422 The practical effect of this occurs only when not under C<S<use
423 utf8>>, and affects just the C1 controls (code points 0x80 through
424 0xFF), NO-BREAK SPACE, and SOFT HYPHEN.
426 =head2 Inlining of C<sub () { $var }> with observable side-effects
428 In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
429 subroutine, capturing the value of C<$var> at the time the C<sub> expression
430 is evaluated. This can break the closure behavior in those cases where
431 C<$var> is subsequently modified, since the subroutine won't return the
432 changed value. (Note that this all only applies to anonymous subroutines
433 with an empty prototype (S<C<sub ()>>).)
435 This usage is now deprecated in those cases where the variable could be
436 modified elsewhere. Perl detects those cases and emits a deprecation
437 warning. Such code will likely change in the future and stop producing a
440 If your variable is only modified in the place where it is declared, then
441 Perl will continue to make the sub inlinable with no warnings.
445 return sub () { $var }; # fine
448 sub make_constant_deprecated {
451 return sub () { $var }; # deprecated
454 sub make_constant_deprecated2 {
456 log_that_value($var); # could modify $var
457 return sub () { $var }; # deprecated
460 In the second example above, detecting that C<$var> is assigned to only once
461 is too hard to detect. That it happens in a spot other than the C<my>
462 declaration is enough for Perl to find it suspicious.
464 This deprecation warning happens only for a simple variable for the body of
465 the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
466 because it does not become part of the sub's body.) For more complex
467 cases, such as S<C<sub () { do_something() if 0; $var }>> the behavior has
468 changed such that inlining does not happen if the variable is modifiable
469 elsewhere. Such cases should be rare.
471 =head2 Use of multiple C</x> regexp modifiers
473 It is now deprecated to say something like any of the following:
479 That is, now C<x> should only occur once in any string of contiguous
480 regular expression pattern modifiers. We do not believe there are any
481 occurrences of this in all of CPAN. This is in preparation for a future
482 Perl release having C</xx> permit white-space for readability in
483 bracketed character classes (those enclosed in square brackets:
486 =head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now deprecated
488 This non-graphic character is essentially indistinguishable from a
489 regular space, and so should not be allowed. See
490 L<charnames/CUSTOM ALIASES>.
492 =head2 A literal C<"{"> should now be escaped in a pattern
494 If you want a literal left curly bracket (also called a left brace) in a
495 regular expression pattern, you should now escape it by either
496 preceding it with a backslash (C<"\{">) or enclosing it within square
497 brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
498 will be raised. This was first announced as forthcoming in the v5.16
499 release; it will allow future extensions to the language to happen.
501 =head2 Making all warnings fatal is discouraged
503 The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
504 C<< use warnings FATAL => 'all' >> is discouraged, and provides stronger
505 language about the risks of fatal warnings in general.
507 =head1 Performance Enhancements
513 If a method or class name is known at compile time, a hash is precomputed
514 to speed up run-time method lookup. Also, compound method names like
515 C<SUPER::new> are parsed at compile time, to save having to parse them at
520 Array and hash lookups (especially nested ones) that use only constants
521 or simple variables as keys, are now considerably faster. See
522 L</Internal Changes> for more details.
526 C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
527 context. If the right-hand argument is a constant 1, the repetition
528 operator disappears. If the right-hand argument is a constant 0, the whole
529 expression is optimised to the empty list, so long as the left-hand
530 argument is a simple scalar or constant. (That is, C<(foo())x0> is not
531 subject to this optimisation.)
535 C<substr> assignment is now optimised into 4-argument C<substr> at the end
536 of a subroutine (or as the argument to C<return>). Previously, this
537 optimisation only happened in void context.
541 In C<"\L...">, C<"\Q...">, etc., the extra "stringify" op is now optimised
542 away, making these just as fast as C<lcfirst>, C<quotemeta>, etc.
546 Assignment to an empty list is now sometimes faster. In particular, it
547 never calls C<FETCH> on tied arguments on the right-hand side, whereas it
552 There is a performance improvement of up to 20% when C<length> is applied to
553 a non-magical, non-tied string, and either C<use bytes> is in scope or the
554 string doesn't use UTF-8 internally.
558 On most perl builds with 64-bit integers, memory usage for non-magical,
559 non-tied scalars containing only a floating point value has been reduced
560 by between 8 and 32 bytes, depending on OS.
564 In C<@array = split>, the assignment can be optimized away, so that C<split>
565 writes directly to the array. This optimisation was happening only for
566 package arrays other than C<@_>, and only sometimes. Now this
567 optimisation happens almost all the time.
571 C<join> is now subject to constant folding. So for example
572 S<C<join "-", "a", "b">> is converted at compile-time to C<"a-b">.
573 Moreover, C<join> with a scalar or constant for the separator and a
574 single-item list to join is simplified to a stringification, and the
575 separator doesn't even get evaluated.
579 C<qq(@array)> is implemented using two ops: a stringify op and a join op.
580 If the C<qq> contains nothing but a single array, the stringification is
585 S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
586 run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
587 skipped over. The same applies to C<state> variables.
591 Many internal functions have been refactored to improve performance and reduce
592 their memory footprints.
593 L<[GH #13659]|https://github.com/Perl/perl5/issues/13659>
594 L<[GH #13856]|https://github.com/Perl/perl5/issues/13856>
595 L<[GH #13874]|https://github.com/Perl/perl5/issues/13874>
599 C<-T> and C<-B> filetests will return sooner when an empty file is detected.
600 L<[GH #13686]|https://github.com/Perl/perl5/issues/13686>
604 Hash lookups where the key is a constant are faster.
608 Subroutines with an empty prototype and a body containing just C<undef> are now
609 eligible for inlining.
610 L<[GH #14077]|https://github.com/Perl/perl5/issues/14077>
614 Subroutines in packages no longer need to be stored in typeglobs:
615 declaring a subroutine will now put a simple sub reference directly in the
616 stash if possible, saving memory. The typeglob still notionally exists,
617 so accessing it will cause the stash entry to be upgraded to a typeglob
618 (I<i.e.> this is just an internal implementation detail).
619 This optimization does not currently apply to XSUBs or exported
620 subroutines, and method calls will undo it, since they cache things in
622 L<[GH #13392]|https://github.com/Perl/perl5/issues/13392>
626 The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
627 (see L<utf8>) are now optimized out on ASCII platforms. There is now not even
628 a minimal performance hit in writing code portable between ASCII and EBCDIC
633 Win32 Perl uses 8 KB less of per-process memory than before for every perl
634 process, because some data is now memory mapped from disk and shared
635 between processes from the same perl binary.
639 =head1 Modules and Pragmata
641 =head2 Updated Modules and Pragmata
643 Many of the libraries distributed with perl have been upgraded since v5.20.0.
644 For a complete list of changes, run:
646 corelist --diff 5.20.0 5.22.0
648 You can substitute your favorite version in place of 5.20.0, too.
650 Some notable changes include:
656 L<Archive::Tar> has been upgraded to version 2.04.
658 Tests can now be run in parallel.
662 L<attributes> has been upgraded to version 0.27.
664 The usage of C<memEQs> in the XS has been corrected.
665 L<[GH #14072]|https://github.com/Perl/perl5/issues/14072>
667 Avoid reading beyond the end of a buffer. [perl #122629]
671 L<B> has been upgraded to version 1.58.
673 It provides a new C<B::safename> function, based on the existing
674 C<< B::GV->SAFENAME >>, that converts C<\cOPEN> to C<^OPEN>.
676 Nulled COPs are now of class C<B::COP>, rather than C<B::OP>.
678 C<B::REGEXP> objects now provide a C<qr_anoncv> method for accessing the
679 implicit CV associated with C<qr//> things containing code blocks, and a
680 C<compflags> method that returns the pertinent flags originating from the
683 C<B::PMOP> now provides a C<pmregexp> method returning a C<B::REGEXP> object.
684 Two new classes, C<B::PADNAME> and C<B::PADNAMELIST>, have been introduced.
686 A bug where, after an ithread creation or pseudofork, special/immortal SVs in
687 the child ithread/pseudoprocess did not have the correct class of
688 C<B::SPECIAL>, has been fixed.
689 The C<id> and C<outid> PADLIST methods have been added.
693 L<B::Concise> has been upgraded to version 0.996.
695 Null ops that are part of the execution chain are now given sequence
698 Private flags for nulled ops are now dumped with mnemonics as they would be
699 for the non-nulled counterparts.
703 L<B::Deparse> has been upgraded to version 1.35.
705 It now deparses C<+sub : attr { ... }> correctly at the start of a
706 statement. Without the initial C<+>, C<sub> would be a statement label.
708 C<BEGIN> blocks are now emitted in the right place most of the time, but
709 the change unfortunately introduced a regression, in that C<BEGIN> blocks
710 occurring just before the end of the enclosing block may appear below it
713 C<B::Deparse> no longer puts erroneous C<local> here and there, such as for
714 C<LIST = tr/a//d>. [perl #119815]
716 Adjacent C<use> statements are no longer accidentally nested if one
717 contains a C<do> block. [perl #115066]
719 Parenthesised arrays in lists passed to C<\> are now correctly deparsed
720 with parentheses (I<e.g.>, C<\(@a, (@b), @c)> now retains the parentheses
721 around @b), thus preserving the flattening behavior of referenced
722 parenthesised arrays. Formerly, it only worked for one array: C<\(@a)>.
724 C<local our> is now deparsed correctly, with the C<our> included.
726 C<for($foo; !$bar; $baz) {...}> was deparsed without the C<!> (or C<not>).
729 Core keywords that conflict with lexical subroutines are now deparsed with
730 the C<CORE::> prefix.
732 C<foreach state $x (...) {...}> now deparses correctly with C<state> and
735 C<our @array = split(...)> now deparses correctly with C<our> in those
736 cases where the assignment is optimized away.
738 It now deparses C<our(I<LIST>)> and typed lexical (C<my Dog $spot>) correctly.
740 Deparse C<$#_> as that instead of as C<$#{_}>.
741 L<[GH #14545]|https://github.com/Perl/perl5/issues/14545>
743 BEGIN blocks at the end of the enclosing scope are now deparsed in the
744 right place. [perl #77452]
746 BEGIN blocks were sometimes deparsed as __ANON__, but are now always called
749 Lexical subroutines are now fully deparsed. [perl #116553]
751 C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.
753 The op trees that make up regexp code blocks are now deparsed for real.
754 Formerly, the original string that made up the regular expression was used.
755 That caused problems with C<qr/(?{E<lt>E<lt>heredoc})/> and multiline code blocks,
756 which were deparsed incorrectly. [perl #123217] [perl #115256]
758 C<$;> at the end of a statement no longer loses its semicolon.
761 Some cases of subroutine declarations stored in the stash in shorthand form
764 Non-ASCII characters are now consistently escaped in strings, instead of
765 some of the time. (There are still outstanding problems with regular
766 expressions and identifiers that have not been fixed.)
768 When prototype sub calls are deparsed with C<&> (I<e.g.>, under the B<-P>
769 option), C<scalar> is now added where appropriate, to force the scalar
770 context implied by the prototype.
772 C<require(foo())>, C<do(foo())>, C<goto(foo())> and similar constructs with
773 loop controls are now deparsed correctly. The outer parentheses are not
776 Whitespace is no longer escaped in regular expressions, because it was
777 getting erroneously escaped within C<(?x:...)> sections.
779 C<sub foo { foo() }> is now deparsed with those mandatory parentheses.
781 C</@array/> is now deparsed as a regular expression, and not just
784 C</@{-}/>, C</@{+}/> and C<$#{1}> are now deparsed with the braces, which
785 are mandatory in these cases.
787 In deparsing feature bundles, C<B::Deparse> was emitting C<no feature;> first
788 instead of C<no feature ':all';>. This has been fixed.
790 C<chdir FH> is now deparsed without quotation marks.
792 C<\my @a> is now deparsed without parentheses. (Parenthese would flatten
795 C<system> and C<exec> followed by a block are now deparsed correctly.
796 Formerly there was an erroneous C<do> before the block.
798 C<< use constant QR =E<gt> qr/.../flags >> followed by C<"" =~ QR> is no longer
801 Deparsing C<BEGIN { undef &foo }> with the B<-w> switch enabled started to
802 emit 'uninitialized' warnings in Perl 5.14. This has been fixed.
804 Deparsing calls to subs with a C<(;+)> prototype resulted in an infinite
805 loop. The C<(;$>) C<(_)> and C<(;_)> prototypes were given the wrong
806 precedence, causing C<foo($aE<lt>$b)> to be deparsed without the parentheses.
808 Deparse now provides a defined state sub in inner subs.
812 L<B::Op_private> has been added.
814 L<B::Op_private> provides detailed information about the flags used in the
815 C<op_private> field of perl opcodes.
819 L<bigint>, L<bignum>, L<bigrat> have been upgraded to version 0.39.
821 Document in CAVEATS that using strings as numbers won't always invoke
822 the big number overloading, and how to invoke it. [rt.perl.org #123064]
826 L<Carp> has been upgraded to version 1.36.
828 C<Carp::Heavy> now ignores version mismatches with Carp if Carp is newer
829 than 1.12, since C<Carp::Heavy>'s guts were merged into Carp at that
831 L<[GH #13708]|https://github.com/Perl/perl5/issues/13708>
833 Carp now handles non-ASCII platforms better.
835 Off-by-one error fix for Perl E<lt> 5.14.
839 L<constant> has been upgraded to version 1.33.
841 It now accepts fully-qualified constant names, allowing constants to be defined
842 in packages other than the caller.
846 L<CPAN> has been upgraded to version 2.11.
848 Add support for C<Cwd::getdcwd()> and introduce workaround for a misbehavior
849 seen on Strawberry Perl 5.20.1.
851 Fix C<chdir()> after building dependencies bug.
853 Introduce experimental support for plugins/hooks.
855 Integrate the C<App::Cpan> sources.
857 Do not check recursion on optional dependencies.
859 Sanity check F<META.yml> to contain a hash.
860 L<[cpan #95271]|https://rt.cpan.org/Ticket/Display.html?id=95271>
864 L<CPAN::Meta::Requirements> has been upgraded to version 2.132.
866 Works around limitations in C<version::vpp> detecting v-string magic and adds
867 support for forthcoming L<ExtUtils::MakeMaker> bootstrap F<version.pm> for
868 Perls older than 5.10.0.
872 L<Data::Dumper> has been upgraded to version 2.158.
874 Fixes CVE-2014-4330 by adding a configuration variable/option to limit
875 recursion when dumping deep data structures.
877 Changes to resolve Coverity issues.
878 XS dumps incorrectly stored the name of code references stored in a
880 L<[GH #13911]|https://github.com/Perl/perl5/issues/13911>
884 L<DynaLoader> has been upgraded to version 1.32.
886 Remove C<dl_nonlazy> global if unused in Dynaloader. [perl #122926]
890 L<Encode> has been upgraded to version 2.72.
892 C<piconv> now has better error handling when the encoding name is nonexistent,
893 and a build breakage when upgrading L<Encode> in perl-5.8.2 and earlier has
896 Building in C++ mode on Windows now works.
900 L<Errno> has been upgraded to version 1.23.
902 Add C<-P> to the preprocessor command-line on GCC 5. GCC added extra
903 line directives, breaking parsing of error code definitions. [rt.perl.org
908 L<experimental> has been upgraded to version 0.013.
910 Hardcodes features for Perls older than 5.15.7.
914 L<ExtUtils::CBuilder> has been upgraded to version 0.280221.
916 Fixes a regression on Android.
917 L<[GH #14064]|https://github.com/Perl/perl5/issues/14064>
921 L<ExtUtils::Manifest> has been upgraded to version 1.70.
923 Fixes a bug with C<maniread()>'s handling of quoted filenames and improves
924 C<manifind()> to follow symlinks.
925 L<[GH #14003]|https://github.com/Perl/perl5/issues/14003>
929 L<ExtUtils::ParseXS> has been upgraded to version 3.28.
931 Only declare C<file> unused if we actually define it.
932 Improve generated C<RETVAL> code generation to avoid repeated
933 references to C<ST(0)>. [perl #123278]
934 Broaden and document the C</OBJ$/> to C</REF$/> typemap optimization
935 for the C<DESTROY> method. [perl #123418]
939 L<Fcntl> has been upgraded to version 1.13.
941 Add support for the Linux pipe buffer size C<fcntl()> commands.
945 L<File::Find> has been upgraded to version 1.29.
947 C<find()> and C<finddepth()> will now warn if passed inappropriate or
952 L<File::Glob> has been upgraded to version 1.24.
954 Avoid C<SvIV()> expanding to call C<get_sv()> three times in a few
955 places. [perl #123606]
959 L<HTTP::Tiny> has been upgraded to version 0.054.
961 C<keep_alive> is now fork-safe and thread-safe.
965 L<IO> has been upgraded to version 1.35.
967 The XS implementation has been fixed for the sake of older Perls.
971 L<IO::Socket> has been upgraded to version 1.38.
973 Document the limitations of the C<connected()> method. [perl #123096]
977 L<IO::Socket::IP> has been upgraded to version 0.37.
979 A better fix for subclassing C<connect()>.
980 L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
981 L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>
983 Implements Timeout for C<connect()>.
984 L<[cpan #92075]|https://rt.cpan.org/Ticket/Display.html?id=92075>
988 The libnet collection of modules has been upgraded to version 3.05.
990 Support for IPv6 and SSL to C<Net::FTP>, C<Net::NNTP>, C<Net::POP3> and C<Net::SMTP>.
991 Improvements in C<Net::SMTP> authentication.
995 L<Locale::Codes> has been upgraded to version 3.34.
997 Fixed a bug in the scripts used to extract data from spreadsheets that
998 prevented the SHP currency code from being found.
999 L<[cpan #94229]|https://rt.cpan.org/Ticket/Display.html?id=94229>
1001 New codes have been added.
1005 L<Math::BigInt> has been upgraded to version 1.9997.
1007 Synchronize POD changes from the CPAN release.
1008 C<< Math::BigFloat->blog(x) >> would sometimes return C<blog(2*x)> when
1009 the accuracy was greater than 70 digits.
1010 The result of C<< Math::BigFloat->bdiv() >> in list context now
1011 satisfies C<< x = quotient * divisor + remainder >>.
1013 Correct handling of subclasses.
1014 L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
1015 L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>
1019 L<Module::Metadata> has been upgraded to version 1.000026.
1021 Support installations on older perls with an L<ExtUtils::MakeMaker> earlier
1026 L<overload> has been upgraded to version 1.26.
1028 A redundant C<ref $sub> check has been removed.
1032 The PathTools module collection has been upgraded to version 3.56.
1034 A warning from the B<gcc> compiler is now avoided when building the XS.
1036 Don't turn leading C<//> into C</> on Cygwin. [perl #122635]
1040 L<perl5db.pl> has been upgraded to version 1.49.
1042 The debugger would cause an assertion failure.
1043 L<[GH #14605]|https://github.com/Perl/perl5/issues/14605>
1045 C<fork()> in the debugger under C<tmux> will now create a new window for
1046 the forked process. L<[GH #13602]|https://github.com/Perl/perl5/issues/13602>
1048 The debugger now saves the current working directory on startup and
1049 restores it when you restart your program with C<R> or C<rerun>.
1050 L<[GH #13691]|https://github.com/Perl/perl5/issues/13691>
1054 L<PerlIO::scalar> has been upgraded to version 0.22.
1056 Reading from a position well past the end of the scalar now correctly
1057 returns end of file. [perl #123443]
1059 Seeking to a negative position still fails, but no longer leaves the
1060 file position set to a negation location.
1062 C<eof()> on a C<PerlIO::scalar> handle now properly returns true when
1063 the file position is past the 2GB mark on 32-bit systems.
1065 Attempting to write at file positions impossible for the platform now
1066 fail early rather than wrapping at 4GB.
1070 L<Pod::Perldoc> has been upgraded to version 3.25.
1072 Filehandles opened for reading or writing now have C<:encoding(UTF-8)> set.
1073 L<[cpan #98019]|https://rt.cpan.org/Ticket/Display.html?id=98019>
1077 L<POSIX> has been upgraded to version 1.53.
1079 The C99 math functions and constants (for example C<acosh>, C<isinf>, C<isnan>, C<round>,
1080 C<trunc>; C<M_E>, C<M_SQRT2>, C<M_PI>) have been added.
1082 C<POSIX::tmpnam()> now produces a deprecation warning. [perl #122005]
1086 L<Safe> has been upgraded to version 2.39.
1088 C<reval> was not propagating void context properly.
1092 Scalar-List-Utils has been upgraded to version 1.41.
1094 A new module, L<Sub::Util>, has been added, containing functions related to
1095 CODE refs, including C<subname> (inspired by C<Sub::Identity>) and C<set_subname>
1096 (copied and renamed from C<Sub::Name>).
1097 The use of C<GetMagic> in C<List::Util::reduce()> has also been fixed.
1098 L<[cpan #63211]|https://rt.cpan.org/Ticket/Display.html?id=63211>
1102 L<SDBM_File> has been upgraded to version 1.13.
1104 Simplified the build process. [perl #123413]
1108 L<Time::Piece> has been upgraded to version 1.29.
1110 When pretty printing negative C<Time::Seconds>, the "minus" is no longer lost.
1114 L<Unicode::Collate> has been upgraded to version 1.12.
1116 Version 0.67's improved discontiguous contractions is invalidated by default
1117 and is supported as a parameter C<long_contraction>.
1121 L<Unicode::Normalize> has been upgraded to version 1.18.
1123 The XSUB implementation has been removed in favor of pure Perl.
1127 L<Unicode::UCD> has been upgraded to version 0.61.
1129 A new function L<property_values()|Unicode::UCD/prop_values()>
1130 has been added to return a given property's possible values.
1132 A new function L<charprop()|Unicode::UCD/charprop()>
1133 has been added to return the value of a given property for a given code
1136 A new function L<charprops_all()|Unicode::UCD/charprops_all()>
1137 has been added to return the values of all Unicode properties for a
1140 A bug has been fixed so that L<propaliases()|Unicode::UCD/prop_aliases()>
1141 returns the correct short and long names for the Perl extensions where
1144 A bug has been fixed so that
1145 L<prop_value_aliases()|Unicode::UCD/prop_value_aliases()>
1146 returns C<undef> instead of a wrong result for properties that are Perl
1149 This module now works on EBCDIC platforms.
1153 L<utf8> has been upgraded to version 1.17
1155 A mismatch between the documentation and the code in C<utf8::downgrade()>
1156 was fixed in favor of the documentation. The optional second argument
1157 is now correctly treated as a perl boolean (true/false semantics) and
1162 L<version> has been upgraded to version 0.9909.
1164 Numerous changes. See the F<Changes> file in the CPAN distribution for
1169 L<Win32> has been upgraded to version 0.51.
1171 C<GetOSName()> now supports Windows 8.1, and building in C++ mode now works.
1175 L<Win32API::File> has been upgraded to version 0.1202
1177 Building in C++ mode now works.
1181 L<XSLoader> has been upgraded to version 0.20.
1183 Allow XSLoader to load modules from a different namespace.
1188 =head2 Removed Modules and Pragmata
1190 The following modules (and associated modules) have been removed from the core
1205 =head1 Documentation
1207 =head2 New Documentation
1209 =head3 L<perlunicook>
1211 This document, by Tom Christiansen, provides examples of handling Unicode in
1214 =head2 Changes to Existing Documentation
1222 A note on long doubles has been added.
1233 Note that C<SvSetSV> doesn't do set magic.
1237 C<sv_usepvn_flags> - fix documentation to mention the use of C<Newx> instead of
1240 L<[GH #13835]|https://github.com/Perl/perl5/issues/13835>
1244 Clarify where C<NUL> may be embedded or is required to terminate a string.
1248 Some documentation that was previously missing due to formatting errors is
1253 Entries are now organized into groups rather than by the file where they
1258 Alphabetical sorting of entries is now done consistently (automatically
1259 by the POD generator) to make entries easier to find when scanning.
1269 The syntax of single-character variable names has been brought
1270 up-to-date and more fully explained.
1274 Hexadecimal floating point numbers are described, as are infinity and
1279 =head3 L<perlebcdic>
1285 This document has been significantly updated in the light of recent
1286 improvements to EBCDIC support.
1290 =head3 L<perlfilter>
1296 Added a L<LIMITATIONS|perlfilter/LIMITATIONS> section.
1307 Mention that C<study()> is currently a no-op.
1311 Calling C<delete> or C<exists> on array values is now described as "strongly
1312 discouraged" rather than "deprecated".
1316 Improve documentation of C<< our >>.
1320 C<-l> now notes that it will return false if symlinks aren't supported by the
1322 L<[GH #13695]|https://github.com/Perl/perl5/issues/13695>
1326 Note that C<exec LIST> and C<system LIST> may fall back to the shell on
1327 Win32. Only the indirect-object syntax C<exec PROGRAM LIST> and
1328 C<system PROGRAM LIST> will reliably avoid using the shell.
1330 This has also been noted in L<perlport>.
1332 L<[GH #13907]|https://github.com/Perl/perl5/issues/13907>
1342 The OOK example has been updated to account for COW changes and a change in the
1343 storage of the offset.
1347 Details on C level symbols and libperl.t added.
1351 Information on Unicode handling has been added
1355 Information on EBCDIC handling has been added
1365 A note has been added about running on platforms with non-ASCII
1370 A note has been added about performance testing
1374 =head3 L<perlhacktips>
1380 Documentation has been added illustrating the perils of assuming that
1381 there is no change to the contents of static memory pointed to by the
1382 return values of Perl's wrappers for C library functions.
1386 Replacements for C<tmpfile>, C<atoi>, C<strtol>, and C<strtoul> are now
1391 Updated documentation for the C<test.valgrind> C<make> target.
1392 L<[GH #13658]|https://github.com/Perl/perl5/issues/13658>
1396 Information is given about writing test files portably to non-ASCII
1401 A note has been added about how to get a C language stack backtrace.
1411 Note that the message "Redeclaration of "sendpath" with a different
1412 storage class specifier" is harmless.
1416 =head3 L<perllocale>
1422 Updated for the enhancements in v5.22, along with some clarifications.
1426 =head3 L<perlmodstyle>
1432 Instead of pointing to the module list, we are now pointing to
1433 L<PrePAN|http://prepan.org/>.
1443 Updated for the enhancements in v5.22, along with some clarifications.
1447 =head3 L<perlpodspec>
1453 The specification of the pod language is changing so that the default
1454 encoding of pods that aren't in UTF-8 (unless otherwise indicated) is
1455 CP1252 instead of ISO 8859-1 (Latin1).
1459 =head3 L<perlpolicy>
1465 We now have a code of conduct for the I<< p5p >> mailing list, as documented
1466 in L<< perlpolicy/STANDARDS OF CONDUCT >>.
1470 The conditions for marking an experimental feature as non-experimental are now
1475 Clarification has been made as to what sorts of changes are permissible in
1476 maintenance releases.
1486 Out-of-date VMS-specific information has been fixed and/or simplified.
1490 Notes about EBCDIC have been added.
1500 The description of the C</x> modifier has been clarified to note that
1501 comments cannot be continued onto the next line by escaping them; and
1502 there is now a list of all the characters that are considered whitespace
1507 The new C</n> modifier is described.
1511 A note has been added on how to make bracketed character class ranges
1512 portable to non-ASCII machines.
1516 =head3 L<perlrebackslash>
1522 Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
1526 =head3 L<perlrecharclass>
1532 Clarifications have been added to L<perlrecharclass/Character Ranges>
1533 to the effect C<[A-Z]>, C<[a-z]>, C<[0-9]> and
1534 any subranges thereof in regular expression bracketed character classes
1535 are guaranteed to match exactly what a naive English speaker would
1536 expect them to match, even on platforms (such as EBCDIC) where perl
1537 has to do extra work to accomplish this.
1541 The documentation of Bracketed Character Classes has been expanded to cover the
1542 improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
1552 A new section has been added
1553 L<Assigning to References|perlref/Assigning to References>
1563 Comments added on algorithmic complexity and tied hashes.
1573 An ambiguity in the documentation of the C<...> statement has been corrected.
1574 L<[GH #14054]|https://github.com/Perl/perl5/issues/14054>
1578 The empty conditional in C<< for >> and C<< while >> is now documented
1583 =head3 L<perlunicode>
1589 This has had extensive revisions to bring it up-to-date with current
1590 Unicode support and to make it more readable. Notable is that Unicode
1591 7.0 changed what it should do with non-characters. Perl retains the old
1592 way of handling for reasons of backward compatibility. See
1593 L<perlunicode/Noncharacter code points>.
1597 =head3 L<perluniintro>
1603 Advice for how to make sure your strings and regular expression patterns are
1604 interpreted as Unicode has been updated.
1614 C<$]> is no longer listed as being deprecated. Instead, discussion has
1615 been added on the advantages and disadvantages of using it versus
1616 C<$^V>. C<$OLD_PERL_VERSION> was re-added to the documentation as the long
1621 C<${^ENCODING}> is now marked as deprecated.
1625 The entry for C<%^H> has been clarified to indicate it can only handle
1636 Out-of-date and/or incorrect material has been removed.
1640 Updated documentation on environment and shell interaction in VMS.
1650 Added a discussion of locale issues in XS code.
1656 The following additions or changes have been made to diagnostic output,
1657 including warnings and fatal error messages. For the complete list of
1658 diagnostic messages, see L<perldiag>.
1660 =head2 New Diagnostics
1668 L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1670 (P) An internal request asked to add a scalar entry to something that
1671 wasn't a symbol table entry.
1675 L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1677 (F) You tried to use a hash as a reference, as in
1678 C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1679 used to allow this syntax, but shouldn't have.
1683 L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1685 (F) You tried to use an array as a reference, as in
1686 C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1687 allow this syntax, but shouldn't have.
1691 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()?)">
1693 (F) C<defined()> is not useful on arrays because it
1694 checks for an undefined I<scalar> value. If you want to see if the
1695 array is empty, just use S<C<if (@array) { # not empty }>> for example.
1699 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()?)">
1701 (F) C<defined()> is not usually right on hashes.
1703 Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
1704 becomes true in several non-obvious circumstances, including iterators,
1705 weak references, stash names, even remaining true after S<C<undef %hash>>.
1706 These things make S<C<defined %hash>> fairly useless in practice, so it now
1707 generates a fatal error.
1709 If a check for non-empty is what you wanted then just put it in boolean
1710 context (see L<perldata/Scalar values>):
1716 If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
1717 variable exists then that's never really been reliable, and isn't
1718 a good way to enquire about the features of a package, or whether
1723 L<Cannot chr %f|perldiag/"Cannot chr %f">
1725 (F) You passed an invalid number (like an infinity or not-a-number) to
1730 L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1732 (F) You tried converting an infinity or not-a-number to an unsigned
1733 character, which makes no sense.
1737 L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1739 (F) You tried converting an infinity or not-a-number to a character,
1740 which makes no sense.
1744 L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1746 (F) You tried printing an infinity or not-a-number as a character (C<%c>),
1747 which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
1751 L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1753 (F) You defined a character name which had multiple space
1754 characters in a row. Change them to single spaces. Usually these
1755 names are defined in the C<:alias> import argument to C<use charnames>, but
1756 they could be defined by a translator installed into C<$^H{charnames}>.
1757 See L<charnames/CUSTOM ALIASES>.
1761 L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1763 (F) You defined a character name which ended in a space
1764 character. Remove the trailing space(s). Usually these names are
1765 defined in the C<:alias> import argument to C<use charnames>, but they
1766 could be defined by a translator installed into C<$^H{charnames}>.
1767 See L<charnames/CUSTOM ALIASES>.
1771 L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1773 (F) The C<const> attribute causes an anonymous subroutine to be run and
1774 its value captured at the time that it is cloned. Named subroutines are
1775 not cloned like this, so the attribute does not make sense on them.
1779 L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1781 (F) Something went horribly bad in hexadecimal float handling.
1785 L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1787 (F) You have configured Perl to use long doubles but
1788 the internals of the long double format are unknown,
1789 therefore the hexadecimal float output is impossible.
1793 L<Illegal suidscript|perldiag/"Illegal suidscript">
1795 (F) The script run under suidperl was somehow illegal.
1799 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/">
1801 (F) The two-character sequence C<"(?"> in
1802 this context in a regular expression pattern should be an
1803 indivisible token, with nothing intervening between the C<"(">
1804 and the C<"?">, but you separated them.
1808 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/">
1810 (F) The two-character sequence C<"(*"> in
1811 this context in a regular expression pattern should be an
1812 indivisible token, with nothing intervening between the C<"(">
1813 and the C<"*">, but you separated them.
1817 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/">
1819 (F) The pattern looks like a {min,max} quantifier, but the min or max could not
1820 be parsed as a valid number: either it has leading zeroes, or it represents
1821 too big a number to cope with. The S<<-- HERE> shows where in the regular
1822 expression the problem was discovered. See L<perlre>.
1826 L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1828 (F) You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1829 Perl. The current valid ones are given in
1830 L<perlrebackslash/\b{}, \b, \B{}, \B>.
1834 L<Missing or undefined argument to require|perldiag/Missing or undefined argument to require>
1836 (F) You tried to call C<require> with no argument or with an undefined
1837 value as an argument. C<require> expects either a package name or a
1838 file-specification as an argument. See L<perlfunc/require>.
1840 Formerly, C<require> with no argument or C<undef> warned about a Null filename.
1850 L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
1852 (D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
1853 now emits a warning. It is intended that it will become an error in v5.24.
1854 This character class matches a single byte even if it appears within a
1855 multi-byte character, breaks encapsulation, and can corrupt UTF-8
1860 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>>
1862 (W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1864 You specified a character that has the given plainer way of writing it,
1865 and which is also portable to platforms running with different character
1870 L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1871 as 0 in increment (++)">
1873 (W numeric) The indicated string was fed as an argument to the C<++> operator
1874 which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1875 See L<perlop/Auto-increment and Auto-decrement> for details.
1879 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/">
1881 (W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1883 In a bracketed character class in a regular expression pattern, you
1884 had a range which has exactly one end of it specified using C<\N{}>, and
1885 the other end is specified using a non-portable mechanism. Perl treats
1886 the range as a Unicode range, that is, all the characters in it are
1887 considered to be the Unicode characters, and which may be different code
1888 points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1889 is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1890 matches the characters whose code points in Unicode are 6, 7, and 8.
1891 But that C<\x08> might indicate that you meant something different, so
1892 the warning gets raised.
1896 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".>
1898 (W locale) You are 1) running under "C<use locale>"; 2) the current
1899 locale is not a UTF-8 one; 3) you tried to do the designated case-change
1900 operation on the specified Unicode character; and 4) the result of this
1901 operation would mix Unicode and locale rules, which likely conflict.
1903 The warnings category C<locale> is new.
1907 L<:const is experimental|perldiag/":const is experimental">
1909 (S experimental::const_attr) The C<const> attribute is experimental.
1910 If you want to use the feature, disable the warning with C<no warnings
1911 'experimental::const_attr'>, but know that in doing so you are taking
1912 the risk that your code may break in a future Perl version.
1916 L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1918 (W overflow) You called C<gmtime> with a number that it could not handle:
1919 too large, too small, or NaN. The returned value is C<undef>.
1923 L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1925 (W overflow) The hexadecimal floating point has larger exponent
1926 than the floating point supports.
1930 L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1932 (W overflow) The hexadecimal floating point has smaller exponent
1933 than the floating point supports.
1937 L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1939 (W overflow) The hexadecimal floating point literal had more bits in
1940 the mantissa (the part between the C<0x> and the exponent, also known as
1941 the fraction or the significand) than the floating point supports.
1945 L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1947 (W overflow) The hexadecimal floating point had internally more
1948 digits than could be output. This can be caused by unsupported
1949 long double formats, or by 64-bit integers not being available
1950 (needed to retrieve the digits under some configurations).
1954 L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1956 (W locale) You are using the named locale, which is a non-UTF-8 one, and
1957 which perl has determined is not fully compatible with what it can
1958 handle. The second C<%s> gives a reason.
1960 The warnings category C<locale> is new.
1964 L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1966 (W overflow) You called C<localtime> with a number that it could not handle:
1967 too large, too small, or NaN. The returned value is C<undef>.
1971 L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1973 (W numeric) You tried to execute the
1974 L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1975 times, which doesn't make sense.
1979 L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1981 (D deprecated) You defined a character name which contained a no-break
1982 space character. Change it to a regular space. Usually these names are
1983 defined in the C<:alias> import argument to C<use charnames>, but they
1984 could be defined by a translator installed into C<$^H{charnames}>. See
1985 L<charnames/CUSTOM ALIASES>.
1989 L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
1991 (W numeric) You tried to execute the
1992 L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
1993 C<-Inf>) or NaN times, which doesn't make sense.
1997 L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
1999 (S experimental::win32_perlio) The C<:win32> PerlIO layer is
2000 experimental. If you want to take the risk of using this layer,
2001 simply disable this warning:
2003 no warnings "experimental::win32_perlio";
2007 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>">
2009 (W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2011 Stricter rules help to find typos and other errors. Perhaps you didn't
2012 even intend a range here, if the C<"-"> was meant to be some other
2013 character, or should have been escaped (like C<"\-">). If you did
2014 intend a range, the one that was used is not portable between ASCII and
2015 EBCDIC platforms, and doesn't have an obvious meaning to a casual
2018 [3-7] # OK; Obvious and portable
2019 [d-g] # OK; Obvious and portable
2020 [A-Y] # OK; Obvious and portable
2021 [A-z] # WRONG; Not portable; not clear what is meant
2022 [a-Z] # WRONG; Not portable; not clear what is meant
2023 [%-.] # WRONG; Not portable; not clear what is meant
2024 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
2026 (You can force portability by specifying a Unicode range, which means that
2027 the endpoints are specified by
2028 L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
2029 still not be obvious.)
2030 The stricter rules require that ranges that start or stop with an ASCII
2031 character that is not a control have all their endpoints be a literal
2032 character, and not some escape sequence (like C<"\x41">), and the ranges
2033 must be all digits, or all uppercase letters, or all lowercase letters.
2037 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/">
2039 (W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2041 Stricter rules help to find typos and other errors. You included a
2042 range, and at least one of the end points is a decimal digit. Under the
2043 stricter rules, when this happens, both end points should be digits in
2044 the same group of 10 consecutive digits.
2048 L<Redundant argument in %s|perldiag/Redundant argument in %s>
2050 (W redundant) You called a function with more arguments than were
2051 needed, as indicated by information within other arguments you supplied
2052 (I<e.g>. a printf format). Currently only emitted when a printf-type format
2053 required fewer arguments than were supplied, but might be used in the
2054 future for I<e.g.> L<perlfunc/pack>.
2056 The warnings category C<< redundant >> is new. See also
2057 L<[GH #13534]|https://github.com/Perl/perl5/issues/13534>.
2061 L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
2063 This is not a new diagnostic, but in earlier releases was accidentally
2064 not displayed if the transliteration contained wide characters. This is
2065 now fixed, so that you may see this diagnostic in places where you
2066 previously didn't (but should have).
2070 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">
2072 (W locale) You are matching a regular expression using locale rules,
2073 and a Unicode boundary is being matched, but the locale is not a Unicode
2074 one. This doesn't make sense. Perl will continue, assuming a Unicode
2075 (UTF-8) locale, but the results could well be wrong except if the locale
2076 happens to be ISO-8859-1 (Latin1) where this message is spurious and can
2079 The warnings category C<locale> is new.
2083 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>" >>
2085 (W regexp) You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
2086 portion of a regular expression where the character set modifiers C</a>
2087 or C</aa> are in effect. These two modifiers indicate an ASCII
2088 interpretation, and this doesn't make sense for a Unicode definition.
2089 The generated regular expression will compile so that the boundary uses
2090 all of Unicode. No other portion of the regular expression is affected.
2094 L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
2096 (S experimental::bitwise) This warning is emitted if you use bitwise
2097 operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
2098 Simply suppress the warning if you want to use the feature, but know
2099 that in doing so you are taking the risk of using an experimental
2100 feature which may change or be removed in a future Perl version:
2102 no warnings "experimental::bitwise";
2103 use feature "bitwise";
2108 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/">
2110 (D deprecated, regexp) You used a literal C<"{"> character in a regular
2111 expression pattern. You should change to use C<"\{"> instead, because a future
2112 version of Perl (tentatively v5.26) will consider this to be a syntax error. If
2113 the pattern delimiters are also braces, any matching right brace
2114 (C<"}">) should also be escaped to avoid confusing the parser, for
2121 L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
2123 (D deprecated) Using literal non-graphic (including control)
2124 characters in the source to refer to the I<^FOO> variables, like C<$^X> and
2125 C<${^GLOBAL_PHASE}> is now deprecated.
2129 L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
2131 (W misc) The C<const> attribute has no effect except
2132 on anonymous closure prototypes. You applied it to
2133 a subroutine via L<attributes.pm|attributes>. This is only useful
2134 inside an attribute handler for an anonymous subroutine.
2138 L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
2140 This is not a new diagnostic, but in earlier releases was accidentally
2141 not displayed if the transliteration contained wide characters. This is
2142 now fixed, so that you may see this diagnostic in places where you
2143 previously didn't (but should have).
2147 L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
2149 (S experimental::re_strict) The things that are different when a regular
2150 expression pattern is compiled under C<'strict'> are subject to change
2151 in future Perl releases in incompatible ways; there are also proposals
2152 to change how to enable strict checking instead of using this subpragma.
2153 This means that a pattern that compiles today may not in a future Perl
2154 release. This warning is to alert you to that risk.
2158 L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
2160 L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
2162 (S io) Previously, perl silently ignored any errors when doing an implicit
2163 close of a filehandle, I<i.e.> where the reference count of the filehandle
2164 reached zero and the user's code hadn't already called C<close()>; I<e.g.>
2167 open my $fh, '>', $file or die "open: '$file': $!\n";
2168 print $fh, $data or die;
2169 } # implicit close here
2171 In a situation such as disk full, due to buffering, the error may only be
2172 detected during the final close, so not checking the result of the close is
2175 So perl now warns in such situations.
2179 L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
2181 (W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
2182 one), a multi-byte character was encountered. Perl considers this
2183 character to be the specified Unicode code point. Combining non-UTF-8
2184 locales and Unicode is dangerous. Almost certainly some characters
2185 will have two different representations. For example, in the ISO 8859-7
2186 (Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
2187 also does 0x393. This will make string comparisons unreliable.
2189 You likely need to figure out how this multi-byte character got mixed up
2190 with your single-byte locale (or perhaps you thought you had a UTF-8
2191 locale, but Perl disagrees).
2193 The warnings category C<locale> is new.
2197 =head2 Changes to Existing Diagnostics
2205 This warning has been changed to
2206 L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
2207 to make the issue more identifiable.
2211 L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
2213 The L<perldiag> entry for this warning has added this clarifying note:
2215 Note that for the Inf and NaN (infinity and not-a-number) the
2216 definition of "numeric" is somewhat unusual: the strings themselves
2217 (like "Inf") are considered numeric, and anything following them is
2218 considered non-numeric.
2222 L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
2224 This message has had '(did you forget to declare "my %s"?)' appended to it, to
2225 make it more helpful to new Perl programmers.
2226 L<[GH #13732]|https://github.com/Perl/perl5/issues/13732>
2230 '"my" variable &foo::bar can't be in a package' has been reworded to say
2231 'subroutine' instead of 'variable'.
2235 L<<< \N{} in character class restricted to one character in regex; marked by
2236 S<< <-- HERE >> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character
2237 class or as a range end-point is restricted to one character in regex;
2238 marked by <-- HERE in m/%s/" >>>
2240 This message has had I<character class> changed to I<inverted character
2241 class or as a range end-point is> to reflect improvements in
2242 C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
2246 L<panic: frexp|perldiag/"panic: frexp: %f">
2248 This message has had ': C<%f>' appended to it, to show what the offending
2249 floating point number is.
2253 I<Possible precedence problem on bitwise %c operator> reworded as
2254 L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
2258 L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
2260 This warning is now only produced when the newline is at the end of
2265 "Variable C<%s> will not stay shared" has been changed to say "Subroutine"
2266 when it is actually a lexical sub that will not stay shared.
2270 L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
2272 The L<perldiag> entry for this warning has had information about Unicode
2277 =head2 Diagnostic Removals
2283 "Ambiguous use of -foo resolved as -&foo()"
2285 There is actually no ambiguity here, and this impedes the use of negated
2286 constants; I<e.g.>, C<-Inf>.
2290 "Constant is not a FOO reference"
2292 Compile-time checking of constant dereferencing (I<e.g.>, C<< my_constant->() >>)
2293 has been removed, since it was not taking overloading into account.
2294 L<[GH #9891]|https://github.com/Perl/perl5/issues/9891>
2295 L<[GH #14044]|https://github.com/Perl/perl5/issues/14044>
2299 =head1 Utility Changes
2301 =head2 F<find2perl>, F<s2p> and F<a2p> removal
2307 The F<x2p/> directory has been removed from the Perl core.
2309 This removes find2perl, s2p and a2p. They have all been released to CPAN as
2310 separate distributions (C<App::find2perl>, C<App::s2p>, C<App::a2p>).
2320 F<h2ph> now handles hexadecimal constants in the compiler's predefined
2321 macro definitions, as visible in C<$Config{cppsymbols}>.
2322 L<[GH #14491]|https://github.com/Perl/perl5/issues/14491>.
2332 No longer depends on non-core modules.
2336 =head1 Configuration and Compilation
2342 F<Configure> now checks for C<lrintl()>, C<lroundl()>, C<llrintl()>, and
2347 F<Configure> with C<-Dmksymlinks> should now be faster.
2348 L<[GH #13890]|https://github.com/Perl/perl5/issues/13890>.
2352 The C<pthreads> and C<cl> libraries will be linked by default if present.
2353 This allows XS modules that require threading to work on non-threaded
2354 perls. Note that you must still pass C<-Dusethreads> if you want a
2359 To get more precision and range for floating point numbers one can now
2360 use the GCC quadmath library which implements the quadruple precision
2361 floating point numbers on x86 and IA-64 platforms. See F<INSTALL> for
2366 MurmurHash64A and MurmurHash64B can now be configured as the internal hash
2371 C<make test.valgrind> now supports parallel testing.
2375 TEST_JOBS=9 make test.valgrind
2377 See L<perlhacktips/valgrind> for more information.
2379 L<[GH #13658]|https://github.com/Perl/perl5/issues/13658>
2383 The MAD (Misc Attribute Decoration) build option has been removed
2385 This was an unmaintained attempt at preserving
2386 the Perl parse tree more faithfully so that automatic conversion of
2387 Perl 5 to Perl 6 would have been easier.
2389 This build-time configuration option had been unmaintained for years,
2390 and had probably seriously diverged on both Perl 5 and Perl 6 sides.
2394 A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
2395 see the discussion below at L<< /Internal Changes >>.
2399 Pathtools no longer tries to load XS on miniperl. This speeds up building perl
2410 F<t/porting/re_context.t> has been added to test that L<utf8> and its
2411 dependencies only use the subset of the C<$1..$n> capture vars that
2412 C<Perl_save_re_context()> is hard-coded to localize, because that function
2413 has no efficient way of determining at runtime what vars to localize.
2417 Tests for performance issues have been added in the file F<t/perf/taint.t>.
2421 Some regular expression tests are written in such a way that they will
2422 run very slowly if certain optimizations break. These tests have been
2423 moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
2424 and are run with a C<< watchdog() >>.
2428 C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
2429 more compatible with C<< Test::More >>.
2433 A new test script, F<op/infnan.t>, has been added to test if infinity and NaN are
2434 working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
2438 =head1 Platform Support
2440 =head2 Regained Platforms
2444 =item IRIX and Tru64 platforms are working again.
2446 Some C<make test> failures remain:
2447 L<[GH #14557]|https://github.com/Perl/perl5/issues/14557>
2448 and L<[GH #14727]|https://github.com/Perl/perl5/issues/14727>
2449 for IRIX; L<[GH #14629]|https://github.com/Perl/perl5/issues/14629>,
2450 L<[cpan #99605]|https://rt.cpan.org/Public/Bug/Display.html?id=99605>, and
2451 L<[cpan #104836]|https://rt.cpan.org/Ticket/Display.html?id=104836> for Tru64.
2453 =item z/OS running EBCDIC Code Page 1047
2455 Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
2456 even though support wasn't officially withdrawn, recent perls would not compile
2457 and run well. Perl 5.20 would work, but had many bugs which have now been
2458 fixed. Many CPAN modules that ship with Perl still fail tests, including
2459 C<Pod::Simple>. However the version of C<Pod::Simple> currently on CPAN should work;
2460 it was fixed too late to include in Perl 5.22. Work is under way to fix many
2461 of the still-broken CPAN modules, which likely will be installed on CPAN when
2462 completed, so that you may not have to wait until Perl 5.24 to get a working
2467 =head2 Discontinued Platforms
2471 =item NeXTSTEP/OPENSTEP
2473 NeXTSTEP was a proprietary operating system bundled with NeXT's
2474 workstations in the early to mid 90s; OPENSTEP was an API specification
2475 that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
2476 are now long dead, so support for building Perl on them has been removed.
2480 =head2 Platform-Specific Notes
2486 Special handling is required of the perl interpreter on EBCDIC platforms
2487 to get C<qr/[i-j]/> to match only C<"i"> and C<"j">, since there are 7
2488 characters between the
2489 code points for C<"i"> and C<"j">. This special handling had only been
2490 invoked when both ends of the range are literals. Now it is also
2491 invoked if any of the C<\N{...}> forms for specifying a character by
2492 name or Unicode code point is used instead of a literal. See
2493 L<perlrecharclass/Character Ranges>.
2497 The archname now distinguishes use64bitint from use64bitall.
2501 Build support has been improved for cross-compiling in general and for
2502 Android in particular.
2510 When spawning a subprocess without waiting, the return value is now
2515 Fix a prototype so linking doesn't fail under the VMS C++ compiler.
2519 C<finite>, C<finitel>, and C<isfinite> detection has been added to
2520 C<configure.com>, environment handling has had some minor changes, and
2521 a fix for legacy feature checking status.
2531 F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
2532 builds to complete on GCC 4.8.
2533 L<[GH #14556]|https://github.com/Perl/perl5/issues/14556>
2537 C<nmake minitest> now works on Win32. Due to dependency issues you
2538 need to build C<nmake test-prep> first, and a small number of the
2540 L<[GH #14318]|https://github.com/Perl/perl5/issues/14318>
2544 Perl can now be built in C++ mode on Windows by setting the makefile macro
2545 C<USE_CPLUSPLUS> to the value "define".
2549 The list form of piped open has been implemented for Win32. Note: unlike
2550 C<system LIST> this does not fall back to the shell.
2551 L<[GH #13574]|https://github.com/Perl/perl5/issues/13574>
2555 New C<DebugSymbols> and C<DebugFull> configuration options added to
2560 Previously, compiling XS modules (including CPAN ones) using Visual C++ for
2561 Win64 resulted in around a dozen warnings per file from F<hv_func.h>. These
2562 warnings have been silenced.
2566 Support for building without PerlIO has been removed from the Windows
2567 makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
2568 already not supported by F<Configure> on POSIX systems.
2572 Between 2 and 6 milliseconds and seven I/O calls have been saved per attempt
2573 to open a perl module for each path in C<@INC>.
2577 Intel C builds are now always built with C99 mode on.
2581 C<%I64d> is now being used instead of C<%lld> for MinGW.
2585 In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
2586 opening F</dev/null> (which works under Win32 Perl's default C<:unix>
2587 layer) was implemented for C<:win32>.
2588 L<[GH #13968]|https://github.com/Perl/perl5/issues/13968>
2592 A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
2593 dmake makefile for gcc builds only. Set this to "define" if you want perl to
2594 use long doubles to give more accuracy and range for floating point numbers.
2600 On OpenBSD, Perl will now default to using the system C<malloc> due to the
2601 security features it provides. Perl's own malloc wrapper has been in use
2602 since v5.14 due to performance reasons, but the OpenBSD project believes
2603 the tradeoff is worth it and would prefer that users who need the speed
2604 specifically ask for it.
2606 L<[GH #13888]|https://github.com/Perl/perl5/issues/13888>.
2614 We now look for the Sun Studio compiler in both F</opt/solstudio*> and
2615 F</opt/solarisstudio*>.
2619 Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
2620 didn't follow implied dependencies to build C<perldtrace.h>. Added an
2621 explicit dependency to C<depend>.
2622 L<[GH #13334]|https://github.com/Perl/perl5/issues/13334>
2626 C99 options have been cleaned up; hints look for C<solstudio>
2627 as well as C<SUNWspro>; and support for native C<setenv> has been added.
2633 =head1 Internal Changes
2639 Experimental support has been added to allow ops in the optree to locate
2640 their parent, if any. This is enabled by the non-default build option
2641 C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
2642 enabled by default, so XS code which directly accesses the C<op_sibling>
2643 field of ops should be updated to be future-proofed.
2645 On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
2646 C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
2647 sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
2648 parent (if any) rather than being C<NULL>.
2650 To make existing code work transparently whether using C<PERL_OP_PARENT>
2651 or not, a number of new macros and functions have been added that should
2652 be used, rather than directly manipulating C<op_sibling>.
2654 For the case of just reading C<op_sibling> to determine the next sibling,
2655 two new macros have been added. A simple scan through a sibling chain
2658 for (; kid->op_sibling; kid = kid->op_sibling) { ... }
2660 should now be written as:
2662 for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
2664 For altering optrees, a general-purpose function C<op_sibling_splice()>
2665 has been added, which allows for manipulation of a chain of sibling ops.
2666 By analogy with the Perl function C<splice()>, it allows you to cut out
2667 zero or more ops from a sibling chain and replace them with zero or more
2668 new ops. It transparently handles all the updating of sibling, parent,
2669 op_last pointers etc.
2671 If you need to manipulate ops at a lower level, then three new macros,
2672 C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
2673 be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
2674 also updating C<op_moresib>. The first sets the sibling pointer to a new
2675 sibling, the second makes the op the last sibling, and the third
2676 conditionally does the first or second action. Note that unlike
2677 C<op_sibling_splice()> these macros won't maintain consistency in the
2678 parent at the same time (I<e.g.> by updating C<op_first> and C<op_last> where
2681 A C-level C<Perl_op_parent()> function and a Perl-level C<B::OP::parent()>
2682 method have been added. The C function only exists under
2683 C<PERL_OP_PARENT> builds (using it is build-time error on vanilla
2684 perls). C<B::OP::parent()> exists always, but on a vanilla build it
2685 always returns C<NULL>. Under C<PERL_OP_PARENT>, they return the parent
2686 of the current op, if any. The variable C<$B::OP::does_parent> allows you
2687 to determine whether C<B> supports retrieving an op's parent.
2689 C<PERL_OP_PARENT> was introduced in 5.21.2, but the interface was
2690 changed considerably in 5.21.11. If you updated your code before the
2691 5.21.11 changes, it may require further revision. The main changes after
2698 The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
2699 C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
2700 op-manipulating macros.
2704 The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
2709 The macro C<OpSIBLING_set> has been removed, and has been superseded by
2710 C<OpMORESIB_set> I<et al>.
2714 The C<op_sibling_splice()> function now accepts a null C<parent> argument
2715 where the splicing doesn't affect the first or last ops in the sibling
2722 Macros have been created to allow XS code to better manipulate the POSIX locale
2723 category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
2727 The previous C<atoi> I<et al> replacement function, C<grok_atou>, has now been
2728 superseded by C<grok_atoUV>. See L<perlclib> for details.
2732 A new function, C<Perl_sv_get_backrefs()>, has been added which allows you
2733 retrieve the weak references, if any, which point at an SV.
2737 The C<screaminstr()> function has been removed. Although marked as
2738 public API, it was undocumented and had no usage in CPAN modules. Calling
2739 it has been fatal since 5.17.0.
2743 The C<newDEFSVOP()>, C<block_start()>, C<block_end()> and C<intro_my()>
2744 functions have been added to the API.
2748 The internal C<convert> function in F<op.c> has been renamed
2749 C<op_convert_list> and added to the API.
2753 The C<sv_magic()> function no longer forbids "ext" magic on read-only
2754 values. After all, perl can't know whether the custom magic will modify
2756 L<[GH #14202]|https://github.com/Perl/perl5/issues/14202>.
2760 Accessing L<perlapi/CvPADLIST> on an XSUB is now forbidden.
2762 The C<CvPADLIST> field has been reused for a different internal purpose
2763 for XSUBs. So in particular, you can no longer rely on it being NULL as a
2764 test of whether a CV is an XSUB. Use C<CvISXSUB()> instead.
2768 SVs of type C<SVt_NV> are now sometimes bodiless when the build
2769 configuration and platform allow it: specifically, when C<< sizeof(NV) <=
2770 sizeof(IV) >>. "Bodiless" means that the NV value is stored directly in
2771 the head of an SV, without requiring a separate body to be allocated. This
2772 trick has already been used for IVs since 5.9.2 (though in the case of
2773 IVs, it is always used, regardless of platform and build configuration).
2777 The C<$DB::single>, C<$DB::signal> and C<$DB::trace> variables now have set- and
2778 get-magic that stores their values as IVs, and those IVs are used when
2779 testing their values in C<pp_dbstate()>. This prevents perl from
2780 recursing infinitely if an overloaded object is assigned to any of those
2782 L<[GH #14013]|https://github.com/Perl/perl5/issues/14013>.
2786 C<Perl_tmps_grow()>, which is marked as public API but is undocumented, has
2787 been removed from the public API. This change does not affect XS code that
2788 uses the C<EXTEND_MORTAL> macro to pre-extend the mortal stack.
2792 Perl's internals no longer sets or uses the C<SVs_PADMY> flag.
2793 C<SvPADMY()> now returns a true value for anything not marked C<PADTMP>
2794 and C<SVs_PADMY> is now defined as 0.
2798 The macros C<SETsv> and C<SETsvUN> have been removed. They were no longer used
2799 in the core since commit 6f1401dc2a five years ago, and have not been
2800 found present on CPAN.
2804 The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
2805 David Mitchell for future work on vtables.
2809 The C<sv_catpvn_flags()> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
2810 flags, which specify whether the appended string is bytes or UTF-8,
2811 respectively. (These flags have in fact been present since 5.16.0, but
2812 were formerly not regarded as part of the API.)
2816 A new opcode class, C<< METHOP >>, has been introduced. It holds
2817 information used at runtime to improve the performance
2818 of class/object method calls.
2820 C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> have changed from being
2821 C<< UNOP/SVOP >> to being C<< METHOP >>.
2825 C<cv_name()> is a new API function that can be passed a CV or GV. It
2826 returns an SV containing the name of the subroutine, for use in
2829 L<[GH #12767]|https://github.com/Perl/perl5/issues/12767>
2830 L<[GH #13392]|https://github.com/Perl/perl5/issues/13392>
2834 C<cv_set_call_checker_flags()> is a new API function that works like
2835 C<cv_set_call_checker()>, except that it allows the caller to specify
2836 whether the call checker requires a full GV for reporting the subroutine's
2837 name, or whether it could be passed a CV instead. Whatever value is
2838 passed will be acceptable to C<cv_name()>. C<cv_set_call_checker()>
2839 guarantees there will be a GV, but it may have to create one on the fly,
2840 which is inefficient.
2841 L<[GH #12767]|https://github.com/Perl/perl5/issues/12767>
2845 C<CvGV> (which is not part of the API) is now a more complex macro, which may
2846 call a function and reify a GV. For those cases where it has been used as a
2847 boolean, C<CvHASGV> has been added, which will return true for CVs that
2848 notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
2849 now for lexical subs.
2850 L<[GH #13392]|https://github.com/Perl/perl5/issues/13392>
2854 The L<perlapi/sync_locale> function has been added to the public API.
2855 Changing the program's locale should be avoided by XS code. Nevertheless,
2856 certain non-Perl libraries called from XS need to do so, such as C<Gtk>.
2857 When this happens, Perl needs to be told that the locale has
2858 changed. Use this function to do so, before returning to Perl.
2862 The defines and labels for the flags in the C<op_private> field of OPs are now
2863 auto-generated from data in F<regen/op_private>. The noticeable effect of this
2864 is that some of the flag output of C<Concise> might differ slightly, and the
2865 flag output of S<C<perl -Dx>> may differ considerably (they both use the same set
2866 of labels now). Also, debugging builds now have a new assertion in
2867 C<op_free()> to ensure that the op doesn't have any unrecognized flags set in
2872 The deprecated variable C<PL_sv_objcount> has been removed.
2876 Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
2877 except around operations that need it to be set to the program's
2878 underlying locale. This protects the many XS modules that cannot cope
2879 with the decimal radix character not being a dot. Prior to this
2880 release, Perl initialized this category to "C", but a call to
2881 C<POSIX::setlocale()> would change it. Now such a call will change the
2882 underlying locale of the C<LC_NUMERIC> category for the program, but the
2883 locale exposed to XS code will remain "C". There are new macros
2884 to manipulate the LC_NUMERIC locale, including
2885 C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
2886 C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
2887 See L<perlapi/Locale-related functions and macros>.
2891 A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
2892 efficiently determines if the string given by its parameters begins
2893 with a well-formed UTF-8 encoded character.
2897 The following private API functions had their context parameter removed:
2898 C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
2899 C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
2900 C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
2902 Note that the prefix-less versions of those functions that are part of the
2903 public API, such as C<cast_i32()>, remain unaffected.
2907 The C<PADNAME> and C<PADNAMELIST> types are now separate types, and no
2908 longer simply aliases for SV and AV.
2909 L<[GH #14250]|https://github.com/Perl/perl5/issues/14250>.
2913 Pad names are now always UTF-8. The C<PadnameUTF8> macro always returns
2914 true. Previously, this was effectively the case already, but any support
2915 for two different internal representations of pad names has now been
2920 A new op class, C<UNOP_AUX>, has been added. This is a subclass of
2921 C<UNOP> with an C<op_aux> field added, which points to an array of unions
2922 of UV, SV* etc. It is intended for where an op needs to store more data
2923 than a simple C<op_sv> or whatever. Currently the only op of this type is
2924 C<OP_MULTIDEREF> (see next item).
2928 A new op has been added, C<OP_MULTIDEREF>, which performs one or more
2929 nested array and hash lookups where the key is a constant or simple
2930 variable. For example the expression C<$a[0]{$k}[$i]>, which previously
2931 involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
2932 by a single C<multideref> op. It can also handle C<local>, C<exists> and
2933 C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
2934 using C<aelem>/C<helem>, and single-level array lookup with a small constant
2935 index is still done using C<aelemfast>.
2939 =head1 Selected Bug Fixes
2945 C<close> now sets C<$!>
2947 When an I/O error occurs, the fact that there has been an error is recorded
2948 in the handle. C<close> returns false for such a handle. Previously, the
2949 value of C<$!> would be untouched by C<close>, so the common convention of
2950 writing S<C<close $fh or die $!>> did not work reliably. Now the handle
2951 records the value of C<$!>, too, and C<close> restores it.
2955 C<no re> now can turn off everything that C<use re> enables
2957 Previously, running C<no re> would turn off only a few things. Now it
2958 can turn off all the enabled things. For example, the only way to
2959 stop debugging, once enabled, was to exit the enclosing block; that is
2964 C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long
2965 double builds. Under some build options on GCC 4.8 and later, they used
2966 to either overwrite the zero-initialized padding, or bypass the
2967 initialized buffer entirely. This caused F<op/pack.t> to fail.
2968 L<[GH #14554]|https://github.com/Perl/perl5/issues/14554>
2972 Extending an array cloned from a parent thread could result in "Modification of
2973 a read-only value attempted" errors when attempting to modify the new elements.
2974 L<[GH #14605]|https://github.com/Perl/perl5/issues/14605>
2978 An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
2979 L<[GH #14493]|https://github.com/Perl/perl5/issues/14493>
2983 A possible crashing/looping bug related to compiling lexical subs has been
2985 L<[GH #14596]|https://github.com/Perl/perl5/issues/14596>
2989 UTF-8 now works correctly in function names, in unquoted HERE-document
2990 terminators, and in variable names used as array indexes.
2991 L<[GH #14601]|https://github.com/Perl/perl5/issues/14601>
2995 Repeated global pattern matches in scalar context on large tainted strings were
2996 exponentially slow depending on the current match position in the string.
2997 L<[GH #14238]|https://github.com/Perl/perl5/issues/14238>
3001 Various crashes due to the parser getting confused by syntax errors have been
3003 L<[GH #14496]|https://github.com/Perl/perl5/issues/14496>
3004 L<[GH #14497]|https://github.com/Perl/perl5/issues/14497>
3005 L<[GH #14548]|https://github.com/Perl/perl5/issues/14548>
3006 L<[GH #14564]|https://github.com/Perl/perl5/issues/14564>
3010 C<split> in the scope of lexical C<$_> has been fixed not to fail assertions.
3011 L<[GH #14483]|https://github.com/Perl/perl5/issues/14483>
3015 C<my $x : attr> syntax inside various list operators no longer fails
3017 L<[GH #14500]|https://github.com/Perl/perl5/issues/14500>
3021 An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
3022 identifier) would cause the parser to crash, instead of simply trying the
3023 C<@> as literal. This has been fixed.
3024 L<[GH #14553]|https://github.com/Perl/perl5/issues/14553>
3028 C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
3030 L<[GH #14512]|https://github.com/Perl/perl5/issues/14512>
3034 C<foreach> in scalar context was not pushing an item on to the stack, resulting
3035 in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.)
3036 It has been fixed to return C<undef>.
3037 L<[GH #14569]|https://github.com/Perl/perl5/issues/14569>
3041 Several cases of data used to store environment variable contents in core C
3042 code being potentially overwritten before being used have been fixed.
3043 L<[GH #14476]|https://github.com/Perl/perl5/issues/14476>
3047 Some patterns starting with C</.*..../> matched against long strings have
3048 been slow since v5.8, and some of the form C</.*..../i> have been slow
3049 since v5.18. They are now all fast again.
3050 L<[GH #14475]|https://github.com/Perl/perl5/issues/14475>.
3054 The original visible value of C<$/> is now preserved when it is set to
3055 an invalid value. Previously if you set C<$/> to a reference to an
3056 array, for example, perl would produce a runtime error and not set
3057 C<PL_rs>, but Perl code that checked C<$/> would see the array
3059 L<[GH #14245]|https://github.com/Perl/perl5/issues/14245>.
3063 In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
3064 be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
3065 warning is issued when something looking like a POSIX class is not
3066 inside a bracketed class. That warning wasn't getting generated when
3067 the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
3071 Perl 5.14.0 introduced a bug whereby S<C<eval { LABEL: }>> would crash. This
3073 L<[GH #14438]|https://github.com/Perl/perl5/issues/14438>.
3077 Various crashes due to the parser getting confused by syntax errors have
3079 L<[GH #14421]|https://github.com/Perl/perl5/issues/14421>.
3080 L<[GH #14472]|https://github.com/Perl/perl5/issues/14472>.
3081 L<[GH #14480]|https://github.com/Perl/perl5/issues/14480>.
3082 L<[GH #14447]|https://github.com/Perl/perl5/issues/14447>.
3086 Code like C</$a[/> used to read the next line of input and treat it as
3087 though it came immediately after the opening bracket. Some invalid code
3088 consequently would parse and run, but some code caused crashes, so this is
3090 L<[GH #14462]|https://github.com/Perl/perl5/issues/14462>.
3094 Fix argument underflow for C<pack>.
3095 L<[GH #14525]|https://github.com/Perl/perl5/issues/14525>.
3099 Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
3100 instead of faulting.
3104 C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
3105 L<[GH #14499]|https://github.com/Perl/perl5/issues/14499>.
3109 The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
3113 Fixed infinite loop in parsing backrefs in regexp patterns.
3117 Several minor bug fixes in behavior of Infinity and NaN, including
3118 warnings when stringifying Infinity-like or NaN-like strings. For example,
3119 "NaNcy" doesn't numify to NaN anymore.
3123 A bug in regular expression patterns that could lead to segfaults and
3124 other crashes has been fixed. This occurred only in patterns compiled
3125 with C</i> while taking into account the current POSIX locale (which usually
3126 means they have to be compiled within the scope of C<S<use locale>>),
3127 and there must be a string of at least 128 consecutive bytes to match.
3128 L<[GH #14389]|https://github.com/Perl/perl5/issues/14389>.
3132 C<s///g> now works on very long strings (where there are more than 2
3133 billion iterations) instead of dying with 'Substitution loop'.
3134 L<[GH #11742]|https://github.com/Perl/perl5/issues/11742>.
3135 L<[GH #14190]|https://github.com/Perl/perl5/issues/14190>.
3139 C<gmtime> no longer crashes with not-a-number values.
3140 L<[GH #14365]|https://github.com/Perl/perl5/issues/14365>.
3144 C<\()> (a reference to an empty list), and C<y///> with lexical C<$_> in
3145 scope, could both do a bad write past the end of the stack. They have
3146 both been fixed to extend the stack first.
3150 C<prototype()> with no arguments used to read the previous item on the
3151 stack, so S<C<print "foo", prototype()>> would print foo's prototype.
3152 It has been fixed to infer C<$_> instead.
3153 L<[GH #14376]|https://github.com/Perl/perl5/issues/14376>.
3157 Some cases of lexical state subs declared inside predeclared subs could
3158 crash, for example when evalling a string including the name of an outer
3159 variable, but no longer do.
3163 Some cases of nested lexical state subs inside anonymous subs could cause
3164 'Bizarre copy' errors or possibly even crashes.
3168 When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
3169 sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
3170 bug, which started to occur in Perl 5.18, has been fixed.
3171 L<[GH #14400]|https://github.com/Perl/perl5/issues/14400>.
3175 Certain syntax errors in substitutions, such as C<< s/${<>{})// >>, would
3176 crash, and had done so since Perl 5.10. (In some cases the crash did not
3177 start happening till 5.16.) The crash has, of course, been fixed.
3178 L<[GH #14391]|https://github.com/Perl/perl5/issues/14391>.
3182 Fix a couple of string grow size calculation overflows; in particular,
3183 a repeat expression like S<C<33 x ~3>> could cause a large buffer
3184 overflow since the new output buffer size was not correctly handled by
3185 C<SvGROW()>. An expression like this now properly produces a memory wrap
3187 L<[GH #14401]|https://github.com/Perl/perl5/issues/14401>.
3191 C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
3192 C<pp_formline()> didn't set the pointer used to mark the chop position,
3193 which led to the C<FF_MORE> case crashing with a segmentation fault.
3194 This has been fixed.
3195 L<[GH #14388]|https://github.com/Perl/perl5/issues/14388>.
3199 A possible buffer overrun and crash when parsing a literal pattern during
3200 regular expression compilation has been fixed.
3201 L<[GH #14416]|https://github.com/Perl/perl5/issues/14416>.
3205 C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
3206 passed a closed file handle.
3207 L<[GH #14073]|https://github.com/Perl/perl5/issues/14073>.
3211 C<op_free()> and C<scalarvoid()> no longer crash due to a stack overflow
3212 when freeing a deeply recursive op tree.
3213 L<[GH #11866]|https://github.com/Perl/perl5/issues/11866>.
3217 In Perl 5.20.0, C<$^N> accidentally had the internal UTF-8 flag turned off
3218 if accessed from a code block within a regular expression, effectively
3219 UTF-8-encoding the value. This has been fixed.
3220 L<[GH #14211]|https://github.com/Perl/perl5/issues/14211>.
3224 A failed C<semctl> call no longer overwrites existing items on the stack,
3225 which means that C<(semctl(-1,0,0,0))[0]> no longer gives an
3226 "uninitialized" warning.
3230 C<else{foo()}> with no space before C<foo> is now better at assigning the
3231 right line number to that statement.
3232 L<[GH #14070]|https://github.com/Perl/perl5/issues/14070>.
3236 Sometimes the assignment in C<@array = split> gets optimised so that C<split>
3237 itself writes directly to the array. This caused a bug, preventing this
3238 assignment from being used in lvalue context. So
3239 C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
3240 Perl 3, when the optimisation was added.) It has now been fixed.
3241 L<[GH #14183]|https://github.com/Perl/perl5/issues/14183>.
3245 When an argument list fails the checks specified by a subroutine
3246 signature (which is still an experimental feature), the resulting error
3247 messages now give the file and line number of the caller, not of the
3249 L<[GH #13643]|https://github.com/Perl/perl5/issues/13643>.
3253 The flip-flop operators (C<..> and C<...> in scalar context) used to maintain
3254 a separate state for each recursion level (the number of times the
3255 enclosing sub was called recursively), contrary to the documentation. Now
3256 each closure has one internal state for each flip-flop.
3257 L<[GH #14110]|https://github.com/Perl/perl5/issues/14110>.
3261 The flip-flop operator (C<..> in scalar context) would return the same
3262 scalar each time, unless the containing subroutine was called recursively.
3263 Now it always returns a new scalar.
3264 L<[GH #14110]|https://github.com/Perl/perl5/issues/14110>.
3268 C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
3269 permitted as the first thing in a C<map> or C<grep> block, the block after
3270 C<print> or C<say> (or other functions) returning a handle, and within
3271 C<${...}>, C<@{...}>, etc.
3272 L<[GH #14088]|https://github.com/Perl/perl5/issues/14088>.
3276 The repetition operator C<x> now propagates lvalue context to its left-hand
3277 argument when used in contexts like C<foreach>. That allows
3278 S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
3283 C<(...) x ...> in scalar context used to corrupt the stack if one operand
3284 was an object with "x" overloading, causing erratic behavior.
3285 L<[GH #13811]|https://github.com/Perl/perl5/issues/13811>.
3289 Assignment to a lexical scalar is often optimised away; for example in
3290 C<my $x; $x = $y + $z>, the assign operator is optimised away and the add
3291 operator writes its result directly to C<$x>. Various bugs related to
3292 this optimisation have been fixed. Certain operators on the right-hand
3293 side would sometimes fail to assign the value at all or assign the wrong
3294 value, or would call STORE twice or not at all on tied variables. The
3295 operators affected were C<$foo++>, C<$foo-->, and C<-$foo> under C<use
3296 integer>, C<chomp>, C<chr> and C<setpgrp>.
3300 List assignments were sometimes buggy if the same scalar ended up on both
3301 sides of the assignment due to use of C<tied>, C<values> or C<each>. The
3302 result would be the wrong value getting assigned.
3306 C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
3307 to mean C<setpgrp(0)>. This has been fixed.
3311 C<__SUB__> could return the wrong value or even corrupt memory under the
3312 debugger (the C<-d> switch) and in subs containing C<eval $string>.
3316 When S<C<sub () { $var }>> becomes inlinable, it now returns a different
3317 scalar each time, just as a non-inlinable sub would, though Perl still
3318 optimises the copy away in cases where it would make no observable
3323 S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
3324 eligible for inlining. The former would crash; the latter would just
3325 throw the attributes away. An exception is made for the little-known
3326 C<:method> attribute, which does nothing much.
3330 Inlining of subs with an empty prototype is now more consistent than
3331 before. Previously, a sub with multiple statements, of which all but the last
3332 were optimised away, would be inlinable only if it were an anonymous sub
3333 containing a string C<eval> or C<state> declaration or closing over an
3334 outer lexical variable (or any anonymous sub under the debugger). Now any
3335 sub that gets folded to a single constant after statements have been
3336 optimised away is eligible for inlining. This applies to things like C<sub
3337 () { jabber() if DEBUG; 42 }>.
3339 Some subroutines with an explicit C<return> were being made inlinable,
3340 contrary to the documentation, Now C<return> always prevents inlining.
3344 On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
3345 scalar assigned to had contained a UTF-8 string previously, then C<crypt>
3346 would not turn off the UTF-8 flag, thus corrupting the return value. This
3347 would happen with S<C<$lexical = crypt ...>>.
3351 C<crypt> no longer calls C<FETCH> twice on a tied first argument.
3355 An unterminated here-doc on the last line of a quote-like operator
3356 (C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
3357 started doing so in 5.18.
3361 C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
3363 L<[GH #13700]|https://github.com/Perl/perl5/issues/13700>.
3367 A small, previously intentional, memory leak in
3368 C<PERL_SYS_INIT>/C<PERL_SYS_INIT3> on Win32 builds was fixed. This might
3369 affect embedders who repeatedly create and destroy perl engines within
3374 C<POSIX::localeconv()> now returns the data for the program's underlying
3375 locale even when called from outside the scope of S<C<use locale>>.
3379 C<POSIX::localeconv()> now works properly on platforms which don't have
3380 C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
3381 to disregard either or both of these locale categories. In such
3382 circumstances, there are now no entries for the corresponding values in
3383 the hash returned by C<localeconv()>.
3387 C<POSIX::localeconv()> now marks appropriately the values it returns as
3388 UTF-8 or not. Previously they were always returned as bytes, even if
3389 they were supposed to be encoded as UTF-8.
3393 On Microsoft Windows, within the scope of C<S<use locale>>, the following
3394 POSIX character classes gave results for many locales that did not
3395 conform to the POSIX standard:
3408 This was because the underlying Microsoft implementation does not
3409 follow the standard. Perl now takes special precautions to correct for
3414 Many issues have been detected by L<Coverity|http://www.coverity.com/> and
3419 C<system()> and friends should now work properly on more Android builds.
3421 Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
3422 would end up being ignored by some of the build process. This caused perls
3423 cross-compiled for Android to end up with defective versions of C<system()>,
3424 C<exec()> and backticks: the commands would end up looking for C</bin/sh>
3425 instead of C</system/bin/sh>, and so would fail for the vast majority
3426 of devices, leaving C<$!> as C<ENOENT>.
3430 C<qr(...\(...\)...)>,
3431 C<qr[...\[...\]...]>,
3433 C<qr{...\{...\}...}>
3434 now work. Previously it was impossible to escape these three
3435 left-characters with a backslash within a regular expression pattern
3436 where otherwise they would be considered metacharacters, and the pattern
3437 opening delimiter was the character, and the closing delimiter was its
3442 C<< s///e >> on tainted UTF-8 strings corrupted C<< pos() >>. This bug,
3443 introduced in 5.20, is now fixed.
3444 L<[GH #13948]|https://github.com/Perl/perl5/issues/13948>.
3448 A non-word boundary in a regular expression (C<< \B >>) did not always
3449 match the end of the string; in particular C<< q{} =~ /\B/ >> did not
3450 match. This bug, introduced in perl 5.14, is now fixed.
3451 L<[GH #13917]|https://github.com/Perl/perl5/issues/13917>.
3455 C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
3456 L<[GH #13954]|https://github.com/Perl/perl5/issues/13954>.
3460 Failing to compile C<use Foo> in an C<eval> could leave a spurious
3461 C<BEGIN> subroutine definition, which would produce a "Subroutine
3462 BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
3464 L<[GH #13926]|https://github.com/Perl/perl5/issues/13926>.
3468 C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
3469 begin with an opening brace.
3470 L<[GH #9085]|https://github.com/Perl/perl5/issues/9085>.
3474 External libraries and Perl may have different ideas of what the locale is.
3475 This is problematic when parsing version strings if the locale's numeric
3476 separator has been changed. Version parsing has been patched to ensure
3477 it handles the locales correctly.
3478 L<[GH #13863]|https://github.com/Perl/perl5/issues/13863>.
3482 A bug has been fixed where zero-length assertions and code blocks inside of a
3483 regex could cause C<pos> to see an incorrect value.
3484 L<[GH #14016]|https://github.com/Perl/perl5/issues/14016>.
3488 Dereferencing of constants now works correctly for typeglob constants. Previously
3489 the glob was stringified and its name looked up. Now the glob itself is used.
3490 L<[GH #9891]|https://github.com/Perl/perl5/issues/9891>
3494 When parsing a sigil (C<$> C<@> C<%> C<&)> followed by braces,
3496 longer tries to guess whether it is a block or a hash constructor (causing a
3497 syntax error when it guesses the latter), since it can only be a block.
3501 S<C<undef $reference>> now frees the referent immediately, instead of hanging on
3502 to it until the next statement.
3503 L<[GH #14032]|https://github.com/Perl/perl5/issues/14032>
3507 Various cases where the name of a sub is used (autoload, overloading, error
3508 messages) used to crash for lexical subs, but have been fixed.
3512 Bareword lookup now tries to avoid vivifying packages if it turns out the
3513 bareword is not going to be a subroutine name.
3517 Compilation of anonymous constants (I<e.g.>, C<sub () { 3 }>) no longer deletes
3518 any subroutine named C<__ANON__> in the current package. Not only was
3519 C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
3524 Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
3525 of the same name declared by C<use constant>. This bug was introduced in Perl
3530 C<qr/[\N{named sequence}]/> now works properly in many instances.
3533 known to C<\N{...}> refer to a sequence of multiple characters, instead of the
3534 usual single character. Bracketed character classes generally only match
3535 single characters, but now special handling has been added so that they can
3536 match named sequences, but not if the class is inverted or the sequence is
3537 specified as the beginning or end of a range. In these cases, the only
3538 behavior change from before is a slight rewording of the fatal error message
3539 given when this class is part of a C<?[...])> construct. When the C<[...]>
3540 stands alone, the same non-fatal warning as before is raised, and only the
3541 first character in the sequence is used, again just as before.
3545 Tainted constants evaluated at compile time no longer cause unrelated
3546 statements to become tainted.
3547 L<[GH #14059]|https://github.com/Perl/perl5/issues/14059>
3551 S<C<open $$fh, ...>>, which vivifies a handle with a name like
3552 C<"main::_GEN_0">, was not giving the handle the right reference count, so
3553 a double free could happen.
3557 When deciding that a bareword was a method name, the parser would get confused
3558 if an C<our> sub with the same name existed, and look up the method in the
3559 package of the C<our> sub, instead of the package of the invocant.
3563 The parser no longer gets confused by C<\U=> within a double-quoted string. It
3564 used to produce a syntax error, but now compiles it correctly.
3565 L<[GH #10882]|https://github.com/Perl/perl5/issues/10882>
3569 It has always been the intention for the C<-B> and C<-T> file test operators to
3570 treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
3571 been updated to say this.) Previously, it was possible for some files to be
3572 considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
3573 operators now work on EBCDIC platforms as well.
3577 Under some conditions warning messages raised during regular expression pattern
3578 compilation were being output more than once. This has now been fixed.
3582 Perl 5.20.0 introduced a regression in which a UTF-8 encoded regular
3583 expression pattern that contains a single ASCII lowercase letter did not
3584 match its uppercase counterpart. That has been fixed in both 5.20.1 and
3586 L<[GH #14051]|https://github.com/Perl/perl5/issues/14051>
3590 Constant folding could incorrectly suppress warnings if lexical warnings
3591 (C<use warnings> or C<no warnings>) were not in effect and C<$^W> were
3592 false at compile time and true at run time.
3596 Loading Unicode tables during a regular expression match could cause assertion
3597 failures under debugging builds if the previous match used the very same
3599 L<[GH #14081]|https://github.com/Perl/perl5/issues/14081>
3603 Thread cloning used to work incorrectly for lexical subs, possibly causing
3604 crashes or double frees on exit.
3608 Since Perl 5.14.0, deleting C<$SomePackage::{__ANON__}> and then undefining an
3609 anonymous subroutine could corrupt things internally, resulting in
3610 L<Devel::Peek> crashing or L<B.pm|B> giving nonsensical data. This has been
3615 S<C<(caller $n)[3]>> now reports names of lexical subs, instead of
3616 treating them as C<"(unknown)">.
3620 C<sort subname LIST> now supports using a lexical sub as the comparison
3625 Aliasing (I<e.g.>, via S<C<*x = *y>>) could confuse list assignments that mention the
3626 two names for the same variable on either side, causing wrong values to be
3628 L<[GH #5788]|https://github.com/Perl/perl5/issues/5788>
3632 Long here-doc terminators could cause a bad read on short lines of input. This
3633 has been fixed. It is doubtful that any crash could have occurred. This bug
3634 goes back to when here-docs were introduced in Perl 3.000 twenty-five years
3639 An optimization in C<split> to treat S<C<split /^/>> like S<C<split /^/m>> had the
3640 unfortunate side-effect of also treating S<C<split /\A/>> like S<C<split /^/m>>,
3641 which it should not. This has been fixed. (Note, however, that S<C<split /^x/>>
3642 does not behave like S<C<split /^x/m>>, which is also considered to be a bug and
3643 will be fixed in a future version.)
3644 L<[GH #14086]|https://github.com/Perl/perl5/issues/14086>
3648 The little-known S<C<my Class $var>> syntax (see L<fields> and L<attributes>)
3649 could get confused in the scope of C<use utf8> if C<Class> were a constant
3650 whose value contained Latin-1 characters.
3654 Locking and unlocking values via L<Hash::Util> or C<Internals::SvREADONLY>
3655 no longer has any effect on values that were read-only to begin with.
3656 Previously, unlocking such values could result in crashes, hangs or
3657 other erratic behavior.
3661 Some unterminated C<(?(...)...)> constructs in regular expressions would
3662 either crash or give erroneous error messages. C</(?(1)/> is one such
3667 S<C<pack "w", $tied>> no longer calls FETCH twice.
3671 List assignments like S<C<($x, $z) = (1, $y)>> now work correctly if C<$x> and
3672 C<$y> have been aliased by C<foreach>.
3676 Some patterns including code blocks with syntax errors, such as
3677 S<C</ (?{(^{})/>>, would hang or fail assertions on debugging builds. Now
3678 they produce errors.
3682 An assertion failure when parsing C<sort> with debugging enabled has been
3684 L<[GH #14087]|https://github.com/Perl/perl5/issues/14087>.
3688 S<C<*a = *b; @a = split //, $b[1]>> could do a bad read and produce junk
3693 In S<C<() = @array = split>>, the S<C<() =>> at the beginning no longer confuses
3694 the optimizer into assuming a limit of 1.
3698 Fatal warnings no longer prevent the output of syntax errors.
3699 L<[GH #14155]|https://github.com/Perl/perl5/issues/14155>.
3703 Fixed a NaN double-to-long-double conversion error on VMS. For quiet NaNs
3704 (and only on Itanium, not Alpha) negative infinity instead of NaN was
3709 Fixed the issue that caused C<< make distclean >> to incorrectly leave some
3711 L<[GH #14108]|https://github.com/Perl/perl5/issues/14108>.
3715 AIX now sets the length in C<< getsockopt >> correctly.
3716 L<[GH #13484]|https://github.com/Perl/perl5/issues/13484>.
3717 L<[cpan #91183]|https://rt.cpan.org/Ticket/Display.html?id=91183>.
3718 L<[cpan #85570]|https://rt.cpan.org/Ticket/Display.html?id=85570>.
3722 The optimization phase of a regexp compilation could run "forever" and
3723 exhaust all memory under certain circumstances; now fixed.
3724 L<[GH #13984]|https://github.com/Perl/perl5/issues/13984>.
3728 The test script F<< t/op/crypt.t >> now uses the SHA-256 algorithm if the
3729 default one is disabled, rather than giving failures.
3730 L<[GH #13715]|https://github.com/Perl/perl5/issues/13715>.
3734 Fixed an off-by-one error when setting the size of a shared array.
3735 L<[GH #14151]|https://github.com/Perl/perl5/issues/14151>.
3739 Fixed a bug that could cause perl to enter an infinite loop during
3740 compilation. In particular, a C<while(1)> within a sublist, I<e.g.>
3742 sub foo { () = ($a, my $b, ($c, do { while(1) {} })) }
3744 The bug was introduced in 5.20.0
3745 L<[GH #14165]|https://github.com/Perl/perl5/issues/14165>.
3749 On Win32, if a variable was C<local>-ized in a pseudo-process that later
3750 forked, restoring the original value in the child pseudo-process caused
3751 memory corruption and a crash in the child pseudo-process (and therefore the
3753 L<[GH #8641]|https://github.com/Perl/perl5/issues/8641>.
3757 Calling C<write> on a format with a C<^**> field could produce a panic
3758 in C<sv_chop()> if there were insufficient arguments or if the variable
3759 used to fill the field was empty.
3760 L<[GH #14255]|https://github.com/Perl/perl5/issues/14255>.
3764 Non-ASCII lexical sub names now appear without trailing junk when they
3765 appear in error messages.
3769 The C<\@> subroutine prototype no longer flattens parenthesized arrays
3770 (taking a reference to each element), but takes a reference to the array
3772 L<[GH #9111]|https://github.com/Perl/perl5/issues/9111>.
3776 A block containing nothing except a C-style C<for> loop could corrupt the
3777 stack, causing lists outside the block to lose elements or have elements
3778 overwritten. This could happen with C<map { for(...){...} } ...> and with
3779 lists containing C<do { for(...){...} }>.
3780 L<[GH #14269]|https://github.com/Perl/perl5/issues/14269>.
3784 C<scalar()> now propagates lvalue context, so that
3785 S<C<for(scalar($#foo)) { ... }>> can modify C<$#foo> through C<$_>.
3789 C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
3790 L<[GH #14292]|https://github.com/Perl/perl5/issues/14292>.
3794 S<C<eval '$variable'>> in nested named subroutines would sometimes look up a
3795 global variable even with a lexical variable in scope.
3799 In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
3800 keyword, started chopping off the last 6 characters and treating the result
3801 as a sort sub name. The previous behavior of treating C<CORE::fake> as a
3802 sort sub name has been restored.
3803 L<[GH #14323]|https://github.com/Perl/perl5/issues/14323>.
3807 Outside of C<use utf8>, a single-character Latin-1 lexical variable is
3808 disallowed. The error message for it, "Can't use global C<$foo>...", was
3809 giving garbage instead of the variable name.
3813 C<readline> on a nonexistent handle was causing C<${^LAST_FH}> to produce a
3814 reference to an undefined scalar (or fail an assertion). Now
3815 C<${^LAST_FH}> ends up undefined.
3819 C<(...) x ...> in void context now applies scalar context to the left-hand
3820 argument, instead of the context the current sub was called in.
3821 L<[GH #14174]|https://github.com/Perl/perl5/issues/14174>.
3825 =head1 Known Problems
3831 C<pack>-ing a NaN on a perl compiled with Visual C 6 does not behave properly,
3832 leading to a test failure in F<t/op/infnan.t>.
3833 L<[GH #14705]|https://github.com/Perl/perl5/issues/14705>
3837 A goal is for Perl to be able to be recompiled to work reasonably well on any
3838 Unicode version. In Perl 5.22, though, the earliest such version is Unicode
3839 5.1 (current is 7.0).
3849 The C<cmp> (and hence C<sort>) operators do not necessarily give the
3850 correct results when both operands are UTF-EBCDIC encoded strings and
3851 there is a mixture of ASCII and/or control characters, along with other
3856 Ranges containing C<\N{...}> in the C<tr///> (and C<y///>)
3857 transliteration operators are treated differently than the equivalent
3858 ranges in regular expression patterns. They should, but don't, cause
3859 the values in the ranges to all be treated as Unicode code points, and
3860 not native ones. (L<perlre/Version 8 Regular Expressions> gives
3861 details as to how it should work.)
3865 Encode and encoding are mostly broken.
3869 Many CPAN modules that are shipped with core show failing tests.
3873 C<pack>/C<unpack> with C<"U0"> format may not work properly.
3879 The following modules are known to have test failures with this version of
3880 Perl. In many cases, patches have been submitted, so there will hopefully be
3887 L<B::Generate> version 1.50
3891 L<B::Utils> version 0.25
3895 L<Coro> version 6.42
3899 L<Dancer> version 1.3130
3903 L<Data::Alias> version 1.18
3907 L<Data::Dump::Streamer> version 2.38
3911 L<Data::Util> version 0.63
3915 L<Devel::Spy> version 0.07
3919 L<invoker> version 0.34
3923 L<Lexical::Var> version 0.009
3927 L<LWP::ConsoleLogger> version 0.000018
3931 L<Mason> version 2.22
3935 L<NgxQueue> version 0.02
3939 L<Padre> version 1.00
3943 L<Parse::Keyword> 0.08
3951 Brian McCauley died on May 8, 2015. He was a frequent poster to Usenet, Perl
3952 Monks, and other Perl forums, and made several CPAN contributions under the
3953 nick NOBULL, including to the Perl FAQ. He attended almost every
3954 YAPC::Europe, and indeed, helped organise YAPC::Europe 2006 and the QA
3955 Hackathon 2009. His wit and his delight in intricate systems were
3956 particularly apparent in his love of board games; many Perl mongers will
3957 have fond memories of playing Fluxx and other games with Brian. He will be
3960 =head1 Acknowledgements
3962 Perl 5.22.0 represents approximately 12 months of development since Perl 5.20.0
3963 and contains approximately 590,000 lines of changes across 2,400 files from 94
3966 Excluding auto-generated files, documentation and release tools, there were
3967 approximately 370,000 lines of changes to 1,500 .pm, .t, .c and .h files.
3969 Perl continues to flourish into its third decade thanks to a vibrant community
3970 of users and developers. The following people are known to have contributed the
3971 improvements that became Perl 5.22.0:
3973 Aaron Crane, Abhijit Menon-Sen, Abigail, Alberto Simões, Alex Solovey, Alex
3974 Vandiver, Alexandr Ciornii, Alexandre (Midnite) Jousset, Andreas König,
3975 Andreas Voegele, Andrew Fresh, Andy Dougherty, Anthony Heading, Aristotle
3976 Pagaltzis, brian d foy, Brian Fraser, Chad Granum, Chris 'BinGOs' Williams,
3977 Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, Darin McBride, Dave
3978 Rolsky, David Golden, David Mitchell, David Wheeler, Dmitri Tikhonov, Doug
3979 Bell, E. Choroba, Ed J, Eric Herman, Father Chrysostomos, George Greer, Glenn
3980 D. Golden, Graham Knop, H.Merijn Brand, Herbert Breunung, Hugo van der Sanden,
3981 James E Keenan, James McCoy, James Raspass, Jan Dubois, Jarkko Hietaniemi,
3982 Jasmine Ngan, Jerry D. Hedden, Jim Cromie, John Goodyear, kafka, Karen
3983 Etheridge, Karl Williamson, Kent Fredric, kmx, Lajos Veres, Leon Timmermans,
3984 Lukas Mai, Mathieu Arnold, Matthew Horsfall, Max Maischein, Michael Bunk,
3985 Nicholas Clark, Niels Thykier, Niko Tyni, Norman Koch, Olivier Mengué, Peter
3986 John Acklam, Peter Martini, Petr Písař, Philippe Bruhat (BooK), Pierre
3987 Bogossian, Rafael Garcia-Suarez, Randy Stauner, Reini Urban, Ricardo Signes,
3988 Rob Hoelz, Rostislav Skudnov, Sawyer X, Shirakata Kentaro, Shlomi Fish,
3989 Sisyphus, Slaven Rezic, Smylers, Steffen Müller, Steve Hay, Sullivan Beck,
3990 syber, Tadeusz Sośnierz, Thomas Sibley, Todd Rinaldo, Tony Cook, Vincent Pit,
3991 Vladimir Marek, Yaroslav Kuzmin, Yves Orton, Ævar Arnfjörð Bjarmason.
3993 The list above is almost certainly incomplete as it is automatically generated
3994 from version control history. In particular, it does not include the names of
3995 the (very much appreciated) contributors who reported issues to the Perl bug
3998 Many of the changes included in this version originated in the CPAN modules
3999 included in Perl's core. We're grateful to the entire CPAN community for
4000 helping Perl to flourish.
4002 For a more complete list of all of Perl's historical contributors, please see
4003 the F<AUTHORS> file in the Perl source distribution.
4005 =head1 Reporting Bugs
4007 If you find what you think is a bug, you might check the articles recently
4008 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
4009 L<https://rt.perl.org/>. There may also be information at
4010 L<http://www.perl.org/>, the Perl Home Page.
4012 If you believe you have an unreported bug, please run the L<perlbug> program
4013 included with your release. Be sure to trim your bug down to a tiny but
4014 sufficient test case. Your bug report, along with the output of C<perl -V>,
4015 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
4017 If the bug you are reporting has security implications, which make it
4018 inappropriate to send to a publicly archived mailing list, then please send it
4019 to perl5-security-report@perl.org. This points to a closed subscription
4020 unarchived mailing list, which includes all the core committers, who will be
4021 able to help assess the impact of issues, figure out a resolution, and help
4022 co-ordinate the release of patches to mitigate or fix the problem across all
4023 platforms on which Perl is supported. Please only use this address for
4024 security issues in the Perl core, not for modules independently distributed on
4029 The F<Changes> file for an explanation of how to view exhaustive details on
4032 The F<INSTALL> file for how to build Perl.
4034 The F<README> file for general stuff.
4036 The F<Artistic> and F<Copying> files for copyright information.