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 require ::Foo::Bar is now illegal.
37 Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
38 bareword require which starts with a double colon dies instead.
40 =head2 Unescaped literal C<"{"> characters in regular expression
41 patterns are no longer permissible
43 You have to now say something like C<"\{"> or C<"[{]"> to specify to
44 match a LEFT CURLY BRACKET. This will allow future extensions to the
45 language. This restriction is not enforced, nor are there current plans
46 to enforce it, if the C<"{"> is the first character in the pattern.
48 These have been deprecated since v5.16, with a deprecation message
49 displayed starting in v5.22.
51 =head2 Literal control character variable names are no longer permissible
53 A variable name may no longer contain a literal control character under
54 any circumstances. These previously were allowed in single-character
55 names on ASCII platforms, but have been deprecated there since Perl
56 v5.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
57 control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
60 =head2 C<qr//xx> is no longer permissible
62 Using more than one C</x> regular expression pattern modifier on a
63 single pattern is now forbidden. This is to allow a future enhancement
64 to the language. This usage has been deprecated since v5.22.
66 =head2 C<NBSP> is no longer permissible in C<\N{...}>
68 The name of a character may no longer contain non-breaking spaces. It
69 has been deprecated to do so since Perl v5.22.
73 XXX Any deprecated features, syntax, modules etc. should be listed here.
75 =head2 Module removals
77 XXX Remove this section if inapplicable.
79 The following modules will be removed from the core distribution in a
80 future release, and will at that time need to be installed from CPAN.
81 Distributions on CPAN which require these modules will need to list them as
84 The core versions of these modules will now issue C<"deprecated">-category
85 warnings to alert you to this fact. To silence these deprecation warnings,
86 install the modules in question from CPAN.
88 Note that these are (with rare exceptions) fine modules that you are encouraged
89 to continue to use. Their disinclusion from core primarily hinges on their
90 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
91 not usually on concerns over their design.
97 XXX Note that deprecated modules should be listed here even if they are listed
98 as an updated module in the L</Modules and Pragmata> section.
102 [ List each other deprecation as a =head2 entry ]
104 =head1 Performance Enhancements
106 XXX Changes which enhance performance without changing behaviour go here.
107 There may well be none in a stable release.
109 [ List each enhancement as a =item entry ]
115 Bareword constant strings are now permitted to take part in constant
116 folding. They were originally exempted from constant folding in August 1999,
117 during the development of Perl 5.6, to ensure that C<use strict "subs">
118 would still apply to bareword constants. That has now been accomplished a
119 different way, so barewords, like other constants, now gain the performance
120 benefits of constant folding.
122 This also means that void-context warnings on constant expressions of
123 barewords now report the folded constant operand, rather than the operation;
124 this matches the behaviour for non-bareword constants.
128 =head1 Modules and Pragmata
130 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
131 go here. If Module::CoreList is updated, generate an initial draft of the
132 following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
133 for important changes should then be added by hand. In an ideal world,
134 dual-life modules would have a F<Changes> file that could be cribbed.
136 [ Within each section, list entries as a =item entry ]
138 =head2 New Modules and Pragmata
148 =head2 Updated Modules and Pragmata
156 L<POSIX> has been upgraded from version 1.68 to 1.69. This remedies several
157 defects in making its symbols exportable. [perl #127821]
161 =head2 Removed Modules and Pragmata
173 XXX Changes to files in F<pod/> go here. Consider grouping entries by
174 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
176 =head2 New Documentation
178 XXX Changes which create B<new> files in F<pod/> go here.
182 XXX Description of the purpose of the new file here
184 =head2 Changes to Existing Documentation
186 XXX Changes which significantly change existing files in F<pod/> go here.
187 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
196 XXX Description of the change here
202 The following additions or changes have been made to diagnostic output,
203 including warnings and fatal error messages. For the complete list of
204 diagnostic messages, see L<perldiag>.
206 XXX New or changed warnings emitted by the core's C<C> code go here. Also
207 include any changes in L<perldiag> that reconcile it to the C<C> code.
209 =head2 New Diagnostics
211 XXX Newly added diagnostic messages go under here, separated into New Errors
220 L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
224 L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
228 L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
232 L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
242 XXX L<message|perldiag/"message">
246 =head2 Changes to Existing Diagnostics
248 XXX Changes (i.e. rewording) of diagnostic messages go here
254 Code like C<$x = $x . "a"> was incorrectly failing to yield a
255 L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
256 warning when C<$x> was a lexical variable with an undefined value. That has
257 now been fixed. [perl #127877]
261 =head1 Utility Changes
263 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
264 Most of these are built within the directory F<utils>.
266 [ List utility changes as a =head2 entry for each utility and =item
267 entries for each change
268 Use L<XXX> with program names to get proper documentation linking. ]
276 Long lines in the message body are now wrapped at 900 characters, to stay
277 well within the 1000-character limit imposed by SMTP mail transfer agents.
278 This is particularly likely to be important for the list of arguments to
279 C<Configure>, which can readily exceed the limit if, for example, it names
280 several non-default installation paths. This change also adds the first unit
281 tests for perlbug. [perl #128020]
285 =head1 Configuration and Compilation
287 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
288 go here. Any other changes to the Perl build process should be listed here.
289 However, any platform-specific changes should be listed in the
290 L</Platform Support> section, instead.
292 [ List changes as a =item entry ].
298 C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
299 invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
300 This means you can supply your target platform C<config.sh>, generate
301 the headers and proceed to build your cross-target perl. [perl #127234]
305 Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
306 counts when the environment variable C<PERL_TRACE_OPS> to be set to a
307 non-zero integer. This allows C<make test> to pass on such a build.
311 When building with GCC 6 and link-time optimization (the C<-flto> option to
312 C<gcc>), C<Configure> was treating all probed symbols as present on the
313 system, regardless of whether they actually exist. This has been fixed.
318 The F<t/test.pl> library is used for internal testing of Perl itself, and
319 also copied by several CPAN modules. Some of those modules must work on
320 older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
321 features. Compatibility with Perl 5.8 was inadvertently removed some time
322 ago; it has now been restored. [perl #128052]
326 The build process no longer emits an extra blank line before building each
327 "simple" extension (those with only F<*.pm> and F<*.pod> files).
333 XXX Any significant changes to the testing of a freshly built perl should be
334 listed here. Changes which create B<new> files in F<t/> go here as do any
335 large changes to the testing harness (e.g. when parallel testing was added).
336 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
337 that they represent may be covered elsewhere.
339 [ List each test improvement as a =item entry ]
349 =head1 Platform Support
351 XXX Any changes to platform support should be listed in the sections below.
353 [ Within the sections, list each platform as a =item entry with specific
354 changes as paragraphs below it. ]
358 XXX List any platforms that this version of perl compiles on, that previous
359 versions did not. These will either be enabled by new files in the F<hints/>
360 directories, or new subdirectories and F<README> files at the top level of the
365 =item XXX-some-platform
371 =head2 Discontinued Platforms
373 XXX List any platforms that this version of perl no longer compiles on.
377 =item XXX-some-platform
383 =head2 Platform-Specific Notes
385 XXX List any changes for specific platforms. This could include configuration
386 and compilation changes or changes in portability/compatibility. However,
387 changes within modules for platforms should generally be listed in the
388 L</Modules and Pragmata> section.
392 =item XXX-some-platform
398 =head1 Internal Changes
400 XXX Changes which affect the interface available to C<XS> code go here. Other
401 significant internal changes for future core maintainers should be noted as
404 [ List each change as a =item entry ]
410 Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
411 default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
412 This flag alters how the C<op_sibling> field is used in C<OP> structures,
413 and has been available optionally since perl 5.22.0.
415 See L<perl5220delta/"Internal Changes"> for more details of what this
420 =head1 Selected Bug Fixes
422 XXX Important bug fixes in the core language are summarized here. Bug fixes in
423 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
425 [ List each fix as a =item entry ]
431 Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
432 and C<or>) were being compiled incorrectly in some cases. If the left-hand
433 side consisted of either a negated bareword constant or a negated C<do {}>
434 block containing a constant expression, and the right-hand side consisted of
435 a negated non-foldable expression, one of the negations was effectively
436 ignored. The same was true of C<if> and C<unless> statement modifiers,
437 though with the left-hand and right-hand sides swapped. This long-standing
438 bug has now been fixed. [perl #127952]
442 =head1 Known Problems
444 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
445 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
446 platform specific bugs also go here.
448 [ List each fix as a =item entry ]
458 =head1 Errata From Previous Releases
464 XXX Add anything here that we forgot to add, or were mistaken about, in
465 the perldelta of a previous release.
471 XXX If any significant core contributor has died, we've added a short obituary
474 =head1 Acknowledgements
478 perl Porting/acknowledgements.pl v5.25.1..HEAD
480 =head1 Reporting Bugs
482 If you find what you think is a bug, you might check the articles recently
483 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
484 L<https://rt.perl.org/> . There may also be information at
485 L<http://www.perl.org/> , the Perl Home Page.
487 If you believe you have an unreported bug, please run the L<perlbug> program
488 included with your release. Be sure to trim your bug down to a tiny but
489 sufficient test case. Your bug report, along with the output of C<perl -V>,
490 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
492 If the bug you are reporting has security implications which make it
493 inappropriate to send to a publicly archived mailing list, then see
494 L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
495 for details of how to report the issue.
499 The F<Changes> file for an explanation of how to view exhaustive details on
502 The F<INSTALL> file for how to build Perl.
504 The F<README> file for general stuff.
506 The F<Artistic> and F<Copying> files for copyright information.