5 perldelta - what is new for perl v5.25.1
9 This document describes differences between the 5.25.0 release and the 5.25.1
12 If you are upgrading from an earlier release such as 5.24.0, first read
13 L<perl5250delta>, which describes differences between 5.24.0 and 5.25.0.
17 XXX Any important notices here
19 =head1 Core Enhancements
21 XXX New core language features go here. Summarize user-visible core language
22 enhancements. Particularly prominent performance optimisations could go
23 here, but most should go in the L</Performance Enhancements> section.
25 [ List each enhancement as a =head2 entry ]
29 XXX Any security-related notices go here. In particular, any security
30 vulnerabilities closed should be noted here rather than in the
31 L</Selected Bug Fixes> section.
33 [ List each security issue as a =head2 entry ]
35 =head2 POSIX::tmpnam() has been removed
37 The fundamentally unsafe C<tmpnam()> interface was deprecated in
38 Perl 5.22.0 and has now been removed. In its place you can use
39 for example the L<File::Temp> interfaces.
41 =head2 require ::Foo::Bar is now illegal.
43 Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
44 bareword require which starts with a double colon dies instead.
46 =head2 Unescaped literal C<"{"> characters in regular expression
47 patterns are no longer permissible
49 You have to now say something like C<"\{"> or C<"[{]"> to specify to
50 match a LEFT CURLY BRACKET. This will allow future extensions to the
51 language. This restriction is not enforced, nor are there current plans
52 to enforce it, if the C<"{"> is the first character in the pattern.
54 These have been deprecated since v5.16, with a deprecation message
55 displayed starting in v5.22.
57 =head2 Literal control character variable names are no longer permissible
59 A variable name may no longer contain a literal control character under
60 any circumstances. These previously were allowed in single-character
61 names on ASCII platforms, but have been deprecated there since Perl
62 v5.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
63 control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
66 =head2 C<qr//xx> is no longer permissible
68 Using more than one C</x> regular expression pattern modifier on a
69 single pattern is now forbidden. This is to allow a future enhancement
70 to the language. This usage has been deprecated since v5.22.
72 =head2 C<NBSP> is no longer permissible in C<\N{...}>
74 The name of a character may no longer contain non-breaking spaces. It
75 has been deprecated to do so since Perl v5.22.
79 XXX Any deprecated features, syntax, modules etc. should be listed here.
81 =head2 Module removals
83 XXX Remove this section if inapplicable.
85 The following modules will be removed from the core distribution in a
86 future release, and will at that time need to be installed from CPAN.
87 Distributions on CPAN which require these modules will need to list them as
90 The core versions of these modules will now issue C<"deprecated">-category
91 warnings to alert you to this fact. To silence these deprecation warnings,
92 install the modules in question from CPAN.
94 Note that these are (with rare exceptions) fine modules that you are encouraged
95 to continue to use. Their disinclusion from core primarily hinges on their
96 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
97 not usually on concerns over their design.
103 XXX Note that deprecated modules should be listed here even if they are listed
104 as an updated module in the L</Modules and Pragmata> section.
108 [ List each other deprecation as a =head2 entry ]
110 =head1 Performance Enhancements
112 XXX Changes which enhance performance without changing behaviour go here.
113 There may well be none in a stable release.
115 [ List each enhancement as a =item entry ]
121 Bareword constant strings are now permitted to take part in constant
122 folding. They were originally exempted from constant folding in August 1999,
123 during the development of Perl 5.6, to ensure that C<use strict "subs">
124 would still apply to bareword constants. That has now been accomplished a
125 different way, so barewords, like other constants, now gain the performance
126 benefits of constant folding.
128 This also means that void-context warnings on constant expressions of
129 barewords now report the folded constant operand, rather than the operation;
130 this matches the behaviour for non-bareword constants.
134 =head1 Modules and Pragmata
136 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
137 go here. If Module::CoreList is updated, generate an initial draft of the
138 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
139 for important changes should then be added by hand. In an ideal world,
140 dual-life modules would have a F<Changes> file that could be cribbed.
142 [ Within each section, list entries as a =item entry ]
144 =head2 New Modules and Pragmata
154 =head2 Updated Modules and Pragmata
160 L<POSIX> has been upgraded from version 1.66 to 1.69. This remedies several
161 defects in making its symbols exportable. [perl #127821] Furthermore,
162 the C<POSIX::tmpnam()> interface has been removed,
163 see L</"POSIX::tmpnam() has been removed">.
167 =head2 Removed Modules and Pragmata
179 XXX Changes to files in F<pod/> go here. Consider grouping entries by
180 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
182 =head2 New Documentation
184 XXX Changes which create B<new> files in F<pod/> go here.
188 XXX Description of the purpose of the new file here
190 =head2 Changes to Existing Documentation
192 XXX Changes which significantly change existing files in F<pod/> go here.
193 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
202 XXX Description of the change here
208 The following additions or changes have been made to diagnostic output,
209 including warnings and fatal error messages. For the complete list of
210 diagnostic messages, see L<perldiag>.
212 XXX New or changed warnings emitted by the core's C<C> code go here. Also
213 include any changes in L<perldiag> that reconcile it to the C<C> code.
215 =head2 New Diagnostics
217 XXX Newly added diagnostic messages go under here, separated into New Errors
226 L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
230 L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
234 L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
238 L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
248 XXX L<message|perldiag/"message">
252 =head2 Changes to Existing Diagnostics
254 XXX Changes (i.e. rewording) of diagnostic messages go here
260 Code like C<$x = $x . "a"> was incorrectly failing to yield a
261 L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
262 warning when C<$x> was a lexical variable with an undefined value. That has
263 now been fixed. [perl #127877]
267 When the error "Experimental push on scalar is now forbidden" is raised for
268 the hash functions C<keys>, C<each>, and C<values>, it is now followed by
269 the more helpful message, "Type of arg 1 to whatever must be hash or
270 array". [perl #127976]
274 C<undef *_; shift> or C<undef *_; pop> inside a subroutine, with no
275 argument to C<shift> or C<pop>, began crashing in Perl 5.14.0, but has now
280 C<< "string$scalar->$*" >> now correctly prefers concat overloading to
281 string overlading if C<< $scalar->$* >> returns an overloaded object,
282 bringing it into consistency with C<$$scalar>.
286 C<< /@0{0*->@*/*0 >> and similar contortions used to crash, but no longer
287 do, but merely produce a syntax error. [perl #128171]
291 C<do> or C<require> with a reference or typeglob which, when stringified,
292 contains a null character started crashing in Perl 5.20.0, but has now been
293 fixed. [perl #128182]
297 =head1 Utility Changes
299 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
300 Most of these are built within the directory F<utils>.
302 [ List utility changes as a =head2 entry for each utility and =item
303 entries for each change
304 Use L<XXX> with program names to get proper documentation linking. ]
312 Long lines in the message body are now wrapped at 900 characters, to stay
313 well within the 1000-character limit imposed by SMTP mail transfer agents.
314 This is particularly likely to be important for the list of arguments to
315 C<Configure>, which can readily exceed the limit if, for example, it names
316 several non-default installation paths. This change also adds the first unit
317 tests for perlbug. [perl #128020]
321 =head1 Configuration and Compilation
323 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
324 go here. Any other changes to the Perl build process should be listed here.
325 However, any platform-specific changes should be listed in the
326 L</Platform Support> section, instead.
328 [ List changes as a =item entry ].
334 C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
335 invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
336 This means you can supply your target platform C<config.sh>, generate
337 the headers and proceed to build your cross-target perl. [perl #127234]
341 Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
342 counts when the environment variable C<PERL_TRACE_OPS> to be set to a
343 non-zero integer. This allows C<make test> to pass on such a build.
347 When building with GCC 6 and link-time optimization (the C<-flto> option to
348 C<gcc>), C<Configure> was treating all probed symbols as present on the
349 system, regardless of whether they actually exist. This has been fixed.
354 The F<t/test.pl> library is used for internal testing of Perl itself, and
355 also copied by several CPAN modules. Some of those modules must work on
356 older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
357 features. Compatibility with Perl 5.8 was inadvertently removed some time
358 ago; it has now been restored. [perl #128052]
362 The build process no longer emits an extra blank line before building each
363 "simple" extension (those with only F<*.pm> and F<*.pod> files).
369 XXX Any significant changes to the testing of a freshly built perl should be
370 listed here. Changes which create B<new> files in F<t/> go here as do any
371 large changes to the testing harness (e.g. when parallel testing was added).
372 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
373 that they represent may be covered elsewhere.
375 [ List each test improvement as a =item entry ]
385 =head1 Platform Support
387 XXX Any changes to platform support should be listed in the sections below.
389 [ Within the sections, list each platform as a =item entry with specific
390 changes as paragraphs below it. ]
394 XXX List any platforms that this version of perl compiles on, that previous
395 versions did not. These will either be enabled by new files in the F<hints/>
396 directories, or new subdirectories and F<README> files at the top level of the
401 =item XXX-some-platform
407 =head2 Discontinued Platforms
409 XXX List any platforms that this version of perl no longer compiles on.
413 =item XXX-some-platform
419 =head2 Platform-Specific Notes
421 XXX List any changes for specific platforms. This could include configuration
422 and compilation changes or changes in portability/compatibility. However,
423 changes within modules for platforms should generally be listed in the
424 L</Modules and Pragmata> section.
428 =item XXX-some-platform
434 =head1 Internal Changes
436 XXX Changes which affect the interface available to C<XS> code go here. Other
437 significant internal changes for future core maintainers should be noted as
440 [ List each change as a =item entry ]
446 Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
447 default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
448 This flag alters how the C<op_sibling> field is used in C<OP> structures,
449 and has been available optionally since perl 5.22.0.
451 See L<perl5220delta/"Internal Changes"> for more details of what this
456 =head1 Selected Bug Fixes
458 XXX Important bug fixes in the core language are summarized here. Bug fixes in
459 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
461 [ List each fix as a =item entry ]
467 Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
468 and C<or>) were being compiled incorrectly in some cases. If the left-hand
469 side consisted of either a negated bareword constant or a negated C<do {}>
470 block containing a constant expression, and the right-hand side consisted of
471 a negated non-foldable expression, one of the negations was effectively
472 ignored. The same was true of C<if> and C<unless> statement modifiers,
473 though with the left-hand and right-hand sides swapped. This long-standing
474 bug has now been fixed. [perl #127952]
478 C<reset> with an argument no longer crashes when encountering stash entries
479 other than globs. [perl #128106]
483 Assignment of hashes to, and deletion of, typeglobs named C<*::::::> no
484 longer causes crashes. [perl #128086]
488 =head1 Known Problems
490 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
491 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
492 platform specific bugs also go here.
494 [ List each fix as a =item entry ]
504 =head1 Errata From Previous Releases
510 XXX Add anything here that we forgot to add, or were mistaken about, in
511 the perldelta of a previous release.
517 XXX If any significant core contributor has died, we've added a short obituary
520 =head1 Acknowledgements
524 perl Porting/acknowledgements.pl v5.25.1..HEAD
526 =head1 Reporting Bugs
528 If you find what you think is a bug, you might check the articles recently
529 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
530 L<https://rt.perl.org/> . There may also be information at
531 L<http://www.perl.org/> , the Perl Home Page.
533 If you believe you have an unreported bug, please run the L<perlbug> program
534 included with your release. Be sure to trim your bug down to a tiny but
535 sufficient test case. Your bug report, along with the output of C<perl -V>,
536 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
538 If the bug you are reporting has security implications which make it
539 inappropriate to send to a publicly archived mailing list, then see
540 L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
541 for details of how to report the issue.
545 The F<Changes> file for an explanation of how to view exhaustive details on
548 The F<INSTALL> file for how to build Perl.
550 The F<README> file for general stuff.
552 The F<Artistic> and F<Copying> files for copyright information.