5 perl5251delta - 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.
15 =head1 Core Enhancements
17 =head2 POSIX::tmpnam() has been removed
19 The fundamentally unsafe C<tmpnam()> interface was deprecated in
20 Perl 5.22.0 and has now been removed. In its place you can use
21 for example the L<File::Temp> interfaces.
23 =head2 require ::Foo::Bar is now illegal.
25 Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
26 bareword require which starts with a double colon dies instead.
28 =head2 Unescaped literal C<"{"> characters in regular expression
29 patterns are no longer permissible
31 You have to now say something like C<"\{"> or C<"[{]"> to specify to
32 match a LEFT CURLY BRACKET. This will allow future extensions to the
33 language. This restriction is not enforced, nor are there current plans
34 to enforce it, if the C<"{"> is the first character in the pattern.
36 These have been deprecated since v5.16, with a deprecation message
37 displayed starting in v5.22.
39 =head2 Literal control character variable names are no longer permissible
41 A variable name may no longer contain a literal control character under
42 any circumstances. These previously were allowed in single-character
43 names on ASCII platforms, but have been deprecated there since Perl
44 v5.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
45 control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
48 =head2 C<qr//xx> is no longer permissible
50 Using more than one C</x> regular expression pattern modifier on a
51 single pattern is now forbidden. This is to allow a future enhancement
52 to the language. This usage has been deprecated since v5.22.
54 =head2 C<NBSP> is no longer permissible in C<\N{...}>
56 The name of a character may no longer contain non-breaking spaces. It
57 has been deprecated to do so since Perl v5.22.
59 =head1 Performance Enhancements
65 Bareword constant strings are now permitted to take part in constant
66 folding. They were originally exempted from constant folding in August 1999,
67 during the development of Perl 5.6, to ensure that C<use strict "subs">
68 would still apply to bareword constants. That has now been accomplished a
69 different way, so barewords, like other constants, now gain the performance
70 benefits of constant folding.
72 This also means that void-context warnings on constant expressions of
73 barewords now report the folded constant operand, rather than the operation;
74 this matches the behaviour for non-bareword constants.
78 =head1 Modules and Pragmata
80 =head2 Updated Modules and Pragmata
86 L<Archive::Tar> has been upgraded from version 2.04 to 2.08.
90 L<Carp> has been upgraded from version 1.40 to 1.41.
94 L<charnames> has been upgraded from version 1.43 to 1.44.
98 L<Config::Perl::V> has been upgraded from version 0.25 to 0.26.
102 L<DB_File> has been upgraded from version 1.835 to 1.838.
106 L<Digest::MD5> has been upgraded from version 2.54 to 2.55.
110 L<IPC::Cmd> has been upgraded from version 0.92 to 0.94.
114 L<IPC::SysV> has been upgraded from version 2.06_01 to 2.07.
118 L<List::Util> has been upgraded from version 1.42_02 to 1.45_01.
122 L<Locale::Codes> has been upgraded from version 3.37 to 3.38.
126 L<Locale::Maketext> has been upgraded from version 1.26 to 1.27.
130 L<Module::CoreList> has been upgraded from version 5.20160507 to 5.20160520.
134 L<Module::Metadata> has been upgraded from version 1.000031 to 1.000032.
138 L<perlfaq> has been upgraded from version 5.021010 to 5.021011.
142 L<POSIX> has been upgraded from version 1.65 to 1.69. This remedies several
143 defects in making its symbols exportable. [perl #127821]
144 The C<POSIX::tmpnam()> interface has been removed,
145 see L</"POSIX::tmpnam() has been removed">.
146 Trying to import POSIX subs that have no real implementations
147 (like C<POSIX::atend()>) now fails at import time, instead of
148 waiting until runtime.
152 L<re> has been upgraded from version 0.32 to 0.33.
156 L<Scalar::Util> has been upgraded from version 1.42_02 to 1.45_01.
160 L<Sys::Syslog> has been upgraded from version 0.33 to 0.34.
164 L<Term::ANSIColor> has been upgraded from version 4.04 to 4.05.
168 L<Test::Simple> has been upgraded from version 1.001014 to 1.302015.
172 L<threads> has been upgraded from version 2.07 to 2.08. Compatibility
173 with 5.8 has been restored.
177 L<threads::shared> has been upgraded from version 1.51 to 1.52.
178 Compatibility with 5.8 has been restored.
184 =head2 Changes to Existing Documentation
190 Fixed link to Crosby paper on hash complexity attack in L<perlsec>.
196 =head2 New Diagnostics
204 L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
208 L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
212 L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
216 L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
220 =head2 Changes to Existing Diagnostics
226 Code like C<$x = $x . "a"> was incorrectly failing to yield a
227 L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
228 warning when C<$x> was a lexical variable with an undefined value. That has
229 now been fixed. [perl #127877]
233 When the error "Experimental push on scalar is now forbidden" is raised for
234 the hash functions C<keys>, C<each>, and C<values>, it is now followed by
235 the more helpful message, "Type of arg 1 to whatever must be hash or
236 array". [perl #127976]
240 C<undef *_; shift> or C<undef *_; pop> inside a subroutine, with no
241 argument to C<shift> or C<pop>, began crashing in Perl 5.14.0, but has now
246 C<< "string$scalar-E<gt>$*" >> now correctly prefers concat overloading to
247 string overloading if C<< $scalar-E<gt>$* >> returns an overloaded object,
248 bringing it into consistency with C<$$scalar>.
252 C<< /@0{0*-E<gt>@*/*0 >> and similar contortions used to crash, but no longer
253 do, but merely produce a syntax error. [perl #128171]
257 C<do> or C<require> with a reference or typeglob which, when stringified,
258 contains a null character started crashing in Perl 5.20.0, but has now been
259 fixed. [perl #128182]
263 =head1 Utility Changes
271 Long lines in the message body are now wrapped at 900 characters, to stay
272 well within the 1000-character limit imposed by SMTP mail transfer agents.
273 This is particularly likely to be important for the list of arguments to
274 C<Configure>, which can readily exceed the limit if, for example, it names
275 several non-default installation paths. This change also adds the first unit
276 tests for perlbug. [perl #128020]
280 =head1 Configuration and Compilation
286 C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
287 invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
288 This means you can supply your target platform C<config.sh>, generate
289 the headers and proceed to build your cross-target perl. [perl #127234]
293 Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
294 counts when the environment variable C<PERL_TRACE_OPS> to be set to a
295 non-zero integer. This allows C<make test> to pass on such a build.
299 When building with GCC 6 and link-time optimization (the C<-flto> option to
300 C<gcc>), C<Configure> was treating all probed symbols as present on the
301 system, regardless of whether they actually exist. This has been fixed.
306 The F<t/test.pl> library is used for internal testing of Perl itself, and
307 also copied by several CPAN modules. Some of those modules must work on
308 older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
309 features. Compatibility with Perl 5.8 was inadvertently removed some time
310 ago; it has now been restored. [perl #128052]
314 The build process no longer emits an extra blank line before building each
315 "simple" extension (those with only F<*.pm> and F<*.pod> files).
319 =head1 Internal Changes
325 Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
326 default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
327 This flag alters how the C<op_sibling> field is used in C<OP> structures,
328 and has been available optionally since perl 5.22.0.
330 See L<perl5220delta/"Internal Changes"> for more details of what this
335 =head1 Selected Bug Fixes
341 Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
342 and C<or>) were being compiled incorrectly in some cases. If the left-hand
343 side consisted of either a negated bareword constant or a negated C<do {}>
344 block containing a constant expression, and the right-hand side consisted of
345 a negated non-foldable expression, one of the negations was effectively
346 ignored. The same was true of C<if> and C<unless> statement modifiers,
347 though with the left-hand and right-hand sides swapped. This long-standing
348 bug has now been fixed. [perl #127952]
352 C<reset> with an argument no longer crashes when encountering stash entries
353 other than globs. [perl #128106]
357 Assignment of hashes to, and deletion of, typeglobs named C<*::::::> no
358 longer causes crashes. [perl #128086]
362 =head1 Acknowledgements
364 Perl 5.25.1 represents approximately 2 weeks of development since Perl 5.25.0
365 and contains approximately 46,000 lines of changes across 630 files from 24
368 Excluding auto-generated files, documentation and release tools, there were
369 approximately 40,000 lines of changes to 510 .pm, .t, .c and .h files.
371 Perl continues to flourish into its third decade thanks to a vibrant community
372 of users and developers. The following people are known to have contributed the
373 improvements that became Perl 5.25.1:
375 Aaron Crane, Andreas Voegele, Chad Granum, Chris 'BinGOs' Williams, Craig A.
376 Berry, David Mitchell, Doug Bell, Father Chrysostomos, H.Merijn Brand, Hugo van
377 der Sanden, Jarkko Hietaniemi, Jerry D. Hedden, Jim Cromie, John Lightsey,
378 Karen Etheridge, Karl Williamson, Lukas Mai, Maxwell Carey, Nicholas Clark,
379 Niko Tyni, Ricardo Signes, Sawyer X, Tony Cook, Yves Orton.
381 The list above is almost certainly incomplete as it is automatically generated
382 from version control history. In particular, it does not include the names of
383 the (very much appreciated) contributors who reported issues to the Perl bug
386 Many of the changes included in this version originated in the CPAN modules
387 included in Perl's core. We're grateful to the entire CPAN community for
388 helping Perl to flourish.
390 For a more complete list of all of Perl's historical contributors, please see
391 the F<AUTHORS> file in the Perl source distribution.
393 =head1 Reporting Bugs
395 If you find what you think is a bug, you might check the articles recently
396 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
397 L<https://rt.perl.org/> . There may also be information at
398 L<http://www.perl.org/> , the Perl Home Page.
400 If you believe you have an unreported bug, please run the L<perlbug> program
401 included with your release. Be sure to trim your bug down to a tiny but
402 sufficient test case. Your bug report, along with the output of C<perl -V>,
403 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
405 If the bug you are reporting has security implications which make it
406 inappropriate to send to a publicly archived mailing list, then see
407 L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
408 for details of how to report the issue.
412 The F<Changes> file for an explanation of how to view exhaustive details on
415 The F<INSTALL> file for how to build Perl.
417 The F<README> file for general stuff.
419 The F<Artistic> and F<Copying> files for copyright information.