5 perldelta - what is new for perl v5.17.1
9 This document describes differences between the 5.17.0 release and
12 If you are upgrading from an earlier release such as 5.16.0, first read
13 L<perl5170delta>, which describes differences between 5.16.0 and
16 =head1 Core Enhancements
18 =head2 More CORE:: subs
20 Several more built-in functions have been added as subroutines to the
21 CORE:: namespace, namely, those non-overridable keywords that can be
22 implemented without custom parsers: C<defined>, C<delete>, C<exists>,
23 C<glob>, C<pos>, C<protoytpe>, C<scalar>, C<split>, C<study>, and C<undef>.
25 As some of these have prototypes, C<prototype('CORE::...')> has been
26 changed to not make a distinction between overridable and non-overridable
27 keywords. This is to make C<prototype('CORE::pos')> consistent with
28 C<prototype(&CORE::pos)>.
30 =head1 Incompatible Changes
32 =head2 C</(?{})/> and C</(??{})/> have been heavily reworked
34 The implementation of this feature has been almost completely rewritten.
35 Although its main intent is to fix bugs, some behaviors, especially
36 related to the scope of lexical variables, will have changed. This is
37 described more fully in the L</Selected Bug Fixes> section.
39 =head2 C<\N{BELL}> now refers to U+1F514 instead of U+0007
41 Unicode 6.0 reused the name "BELL" for a different code point than it
42 traditionally had meant. Since Perl v5.14, use of this name still
43 referred to U+0007, but would raise a deprecation warning. Now, "BELL"
44 refers to U+1F514, and the name for U+0007 is "ALERT". All the
45 functions in L<charnames> have been correspondingly updated.
47 =head2 Alphanumeric operators must now be separated from the closing
48 delimiter of regular expressions
50 You may no longer write something like:
54 Instead you must write
58 with whitespace separating the operator from the closing delimiter of
59 the regular expression. Not having whitespace has resulted in a
60 deprecation warning since Perl v5.14.0.
62 =head2 C<require> dies for unreadable files
64 When C<require> encounters an unreadable file, it now dies. It used to
65 ignore the file and continue searching the directories in @INC
68 =head2 Upgrade to the Unicode 6.2 beta
70 Unicode 6.2 is proposing some changes that may very well break some CPAN
71 modules. The timing of this nicely coincides with Perl's being early in the
72 release cycle. This commit takes the current beta 6.2, adds the proposed
73 changes that aren't yet in it, and subtracts the changes that would affect \X
74 processing, as those turn out to have errors, and may have to be rethought.
75 Unicode has been notified of these problems.
77 This will allow us to gather data as to whether or not the proposed changes
78 cause us problems. These will be presented to Unicode to aid in their final
79 decision as to whether or not to go forward with the changes.
81 These changes will be replaced by the final version of Unicode 6.2 before
84 =head1 Performance Enhancements
90 The C<x> repetition operator is now folded to a single constant at compile
91 time if called in scalar context with constant operands and no parentheses
92 around the left operand.
96 =head1 Modules and Pragmata
98 =head2 Updated Modules and Pragmata
104 L<Archive::Extract> has been upgraded from version 0.58 to 0.60.
106 Work around an edge case on Linux with Busybox's unzip.
110 L<Archive::Tar> has been upgraded from version 1.82 to 1.88.
112 ptar now supports the -T option as well as dashless options
113 [rt.cpan.org #75473], [rt.cpan.org #75475].
115 Auto-encode filenames marked as UTF-8 [rt.cpan.org #75474].
117 Don't use C<tell> on L<IO::Zlib> handles [rt.cpan.org #64339].
119 Don't try to C<chown> on symlinks.
123 L<attributes> has been upgraded from version 0.19 to 0.20.
127 L<autodie> has been upgraded from version 2.10 to 2.11.
131 L<B> has been upgraded from version 1.35 to 1.36.
133 C<B::COP::stashlen> has been replaced with C<B::COP::stashoff>.
135 C<B::COP::stashpv> now supports UTF-8 package names and embedded NULs.
139 L<B::Deparse> has been upgraded from version 1.14 to 1.15.
141 Avoid warning when run under C<perl -w>.
145 L<Class::Struct> has been upgraded from version 0.63 to 0.64.
147 The constructor now respects overridden accessor methods [perl #29230].
151 L<Compress::Raw::Bzip2> has been upgraded from version 2.048 to 2.052.
155 L<Compress::Raw::Zlib> has been upgraded from version 2.048 to 2.054.
157 Upgrade bundled zlib to version 1.2.7.
159 Fix build failures on Irix, Solaris, and Win32, and also when building as C++
160 [rt.cpan.org #69985], [rt.cpan.org #77030], [rt.cpan.org #75222].
164 L<CPAN::Meta> has been upgraded from version 2.120630 to 2.120921.
168 L<CPAN::Meta::Requirements> has been upgraded from version 2.120630 to 2.122.
170 Treat undef requirements to C<from_string_hash> as 0 (with a warning).
172 Added C<requirements_for_module> method.
176 L<CPAN::Meta::YAML> has been upgraded from version 0.007 to 0.008.
180 L<CPANPLUS> has been upgraded from version 0.9121 to 0.9130.
182 Allow adding F<blib/script> to PATH.
184 Save the history between invocations of the shell.
186 Handle multiple C<makemakerargs> and C<makeflags> arguments better.
188 Use C<File::HomeDir> when available, and provide C<PERL5_CPANPLUS_HOME> to
189 override the autodetection.
191 Always re-fetch F<CHECKSUMS> if C<fetchdir> is set.
195 L<Digest::MD5> has been upgraded from version 2.51 to 2.52.
197 Fix C<Digest::Perl::MD5> OO fallback [rt.cpan.org #66634].
201 L<DynaLoader> has been upgraded from version 1.14 to 1.15.
203 This is due to a minor code change in the XS for the VMS implementation.
207 L<ExtUtils::CBuilder> has been upgraded from version 0.280206 to 0.280208.
209 Manifest files are now correctly embedded for those versions of VC++ which
210 make use of them. [perl #111782, #111798].
214 L<File::DosGlob> has been upgraded from version 1.07 to 1.08.
218 L<File::Fetch> has been upgraded from version 0.32 to 0.34.
222 L<File::Spec::Unix> has been upgraded from version 3.39_02 to 3.39_03.
224 C<abs2rel> could produce incorrect results when given two relative paths or
225 the root directory twice [perl #111510].
229 L<Filter::Util::Call> has been upgraded from version 1.40 to 1.45.
233 L<HTTP::Tiny> has been upgraded from version 0.017 to 0.022.
235 Add SSL verification features [github #6], [github #9].
237 Include the final URL in the response hashref.
239 Add C<local_address> option.
243 L<IO> has been upgraded from version 1.25_06 to 1.25_07.
245 C<sync()> can now be called on read-only file handles [perl #64772].
249 L<IPC::Cmd> has been upgraded from version 0.76 to 0.78.
251 Use C<POSIX::_exit> instead of C<exit> in C<run_forked> [rt.cpan.org #76901].
255 L<Memoize> has been upgraded from version 1.02 to 1.03.
257 Fix the C<MERGE> cache option.
261 L<Module::Build> has been upgraded from version 0.39_01 to 0.40.
263 Fixed bug where modules without C<$VERSION> might have a version of '0' listed
264 in 'provides' metadata, which will be rejected by PAUSE.
266 Fixed bug in PodParser to allow numerals in module names.
268 Fixed bug where giving arguments twice led to them becoming arrays, resulting
269 in install paths like F<ARRAY(0xdeadbeef)/lib/Foo.pm>.
273 L<Module::Load::Conditional> has been upgraded from version 0.46 to 0.50.
275 Fix use of C<requires> on perls installed to a path with spaces.
279 L<Object::Accessor> has been upgraded from version 0.42 to 0.44.
283 L<Params::Check> has been upgraded from version 0.32 to 0.36.
287 L<Parse::CPAN::Meta> has been upgraded from version 1.4402 to 1.4404.
291 L<PerlIO::mmap> has been upgraded from version 0.010 to 0.011.
295 L<PerlIO::via::QuotedPrint> has been upgraded from version 0.06 to 0.07.
299 L<Pod::Html> has been upgraded from version 1.15_02 to 1.16.
301 The option C<--libpods> has been reinstated. It is deprecated, and its use
302 does nothing other than issue a warning that it is no longer supported.
304 Since the HTML files generated by pod2html claim to have a UTF-8 charset,
305 actually write the files out using UTF-8 [perl #111446].
309 L<POSIX> has been upgraded from version 1.30 to 1.31.
313 L<re> has been upgraded from version 0.19 to 0.20.
315 See note about C<op_comp> in the L</Internal Changes> section below.
319 L<Safe> has been upgraded from version 2.31_01 to 2.33_01.
321 Fix interactions with C<Devel::Cover>.
323 Don't eval code under C<no strict>.
327 L<Scalar::Util> has been upgraded from version 1.23 to version 1.25.
329 Fix an overloading issue with C<sum>.
331 C<first> and C<reduce> now check the callback first (so C<&first(1)> is
334 Fix C<tainted> on magical values [rt.cpan.org #55763].
336 Fix C<sum> on previously magical values [rt.cpan.org #61118].
338 Fix reading past the end of a fixed buffer [rt.cpan.org #72700].
342 L<Search::Dict> has been upgraded from version 1.04 to 1.07.
344 No longer require C<stat> on filehandles.
346 Use C<fc> for casefolding.
350 L<Storable> has been upgraded from version 2.35 to 2.36.
354 L<Term::ANSIColor> has been upgraded from version 3.01 to 3.02.
356 Add support for italics.
358 Improve error handling.
362 L<Test::Harness> has been upgraded from version 3.23 to 3.25.
364 Fix glob semantics on Win32 [rt.cpan.org #49732].
366 Don't use C<Win32::GetShortPathName> when calling perl [rt.cpan.org #47890].
368 Ignore -T when reading shebang [rt.cpan.org #64404].
370 Handle the case where we don't know the wait status of the test more
373 Make the test summary 'ok' line overridable so that it can be changed to a
374 plugin to make the output of prove idempotent.
376 Don't run world-writable files.
380 L<Unicode::UCD> has been upgraded from version 0.43 to 0.44.
382 This adds a function L<all_casefolds()|Unicode::UCD/all_casefolds()>
383 that returns all the casefolds.
389 =head2 Changes to Existing Documentation
397 L<perlfaq> has been synchronized with version 5.0150040 from CPAN.
407 L<perlcheat> has been reorganized, and a few new sections were added.
413 =head2 Removals of Diagnostics
419 The "Runaway prototype" warning that occurs in bizarre cases has been
420 removed as being unhelpful and inconsistent.
424 The "Not a format reference" error has been removed, as the only case in
425 which it could be triggered was a bug.
429 The "Unable to create sub named %s" error has been removed for the same
434 =head1 Platform Support
436 =head2 Platform-Specific Notes
442 C<link> on Win32 now attempts to set C<$!> to more appropriate values
443 based on the Win32 API error code. [perl #112272]
445 Perl no longer mangles the environment block, e.g. when launching a new
446 sub-process, when the environment contains non-ASCII characters. Known
447 problems still remain, however, when the environment contains characters
448 outside of the current ANSI codepage (e.g. see the item about Unicode in
449 C<%ENV> in L<http://perl5.git.perl.org/perl.git/blob/HEAD:/Porting/todo.pod>).
454 All C header files from the top-level directory of the distribution are now
455 installed on VMS, providing consistency with a long-standing practice on other
456 platforms. Previously only a subset were installed, which broke non-core
457 extension builds for extensions that depended on the missing include files.
461 =head1 Internal Changes
467 The C<study> function was made a no-op in 5.16. It was simply disabled via
468 a C<return> statement; the code was left in place. Now the code supporting
469 what C<study> used to do has been removed.
473 Under threaded perls, there is no longer a separate PV allocated for every
474 COP to store its package name (C<< cop->stashpv >>). Instead, there is an
475 offset (C<< cop->stashoff >>) into the new C<PL_stashpad> array, which
476 holds stash pointers.
480 In the pluggable regex API, the C<regexp_engine> struct has acquired a new
481 field C<op_comp>, which is currently just for perl's internal use, and
482 should be initialised to NULL by other regex plugin modules.
486 A new function C<alloccoptash> has been added to the API, but is considered
487 experimental. See L<perlapi>.
491 =head1 Selected Bug Fixes
497 The implementation of code blocks in regular expressions, such as C<(?{})>
498 and C<(??{})>, has been heavily reworked to eliminate a whole slew of bugs.
499 The main user-visible changes are:
505 Code blocks within patterns are now parsed in the same pass as the
506 surrounding code; in particular it is no longer necessary to have balanced
507 braces: this now works:
511 This means that this error message is longer generated:
513 Sequence (?{...}) not terminated or not {}-balanced in regex
515 but a new error may be seen:
517 Sequence (?{...}) not terminated with ')'
519 In addition, literal code blocks within run-time patterns are only
520 compiled once, at perl compile-time:
523 # this 'FOO' block of code is compiled once,
524 # at the same time as the surrounding 'for' loop
530 Lexical variables are now sane as regards scope, recursion and closure
531 behavior. In particular, C</A(?{B})C/> behaves (from a closure viewpoint)
532 exactly like C</A/ && do { B } && /C/>, while C<qr/A(?{B})C/> is like
533 C<sub {/A/ && do { B } && /C/}>. So this code now works how you might
534 expect, creating three regexes that match 0, 1, and 2:
537 push @r, qr/^(??{$i})$/;
539 "1" =~ $r[1]; # matches
543 The C<use re 'eval'> pragma is now only required for code blocks defined
544 at runtime; in particular in the following, the text of the C<$r> pattern is
545 still interpolated into the new pattern and recompiled, but the individual
546 compiled code-blocks within C<$r> are reused rather than being recompiled,
547 and C<use re 'eval'> isn't needed any more:
549 my $r = qr/abc(?{....})def/;
554 Flow control operators no longer crash. Each code block runs in a new
555 dynamic scope, so C<next> etc. will not see any enclosing loops and
556 C<caller> will not see any calling subroutines. C<return> returns a value
557 from the code block, not from any enclosing subroutine.
561 Perl normally caches the compilation of run-time patterns, and doesn't
562 recompile if the pattern hasn't changed, but this is now disabled if
563 required for the correct behavior of closures. For example:
565 my $code = '(??{$x})';
567 # recompile to see fresh value of $x each time
574 The C</msix> and C<(?msix)> etc. flags are now propagated into the return
575 value from C<(??{})>; this now works:
577 "AB" =~ /a(??{'b'})/i;
581 Warnings and errors will appear to come from the surrounding code (or for
582 run-time code blocks, from an eval) rather than from an C<re_eval>:
584 use re 'eval'; $c = '(?{ warn "foo" })'; /$c/;
589 foo at (re_eval 1) line 1.
590 foo at (re_eval 2) line 1.
594 foo at (eval 1) line 1.
595 foo at /some/prog line 2.
601 Perl now works as well as can be expected on all releases of Unicode so
602 far. In v5.16, it worked on Unicodes 6.0 and 6.1, but there were
603 various bugs for earlier releases; the older the release the more
608 C<vec> no longer produces "uninitialized" warnings in lvalue context
613 An optimization involving fixed strings in regular expressions could cause
614 a severe performance penalty in edge cases. This has been fixed
619 In certain cases, including empty subpatterns within a regular expression (such
620 as C<(?:)> or C<(?:|)>) could disable some optimizations. This has been fixed.
624 The "Can't find an opnumber" message that C<prototype> produces when passed
625 a string like "CORE::nonexistent_keyword" now passes UTF-8 and embedded
626 NULs through unchanged [perl #97478].
630 C<prototype> now treats magical variables like C<$1> the same way as
631 non-magical variables when checking for the CORE:: prefix, instead of
632 treating them as subroutine names.
636 Under threaded perls, a runtime code block in a regular expression could
637 corrupt the package name stored in the op tree, resulting in bad reads
638 in C<caller>, and possibly crashes [perl #113060].
642 Referencing a closure prototype (C<\&{$_[1]}> in an attribute handler for a
643 closure) no longer results in a copy of the subroutine (or assertion
644 failures on debugging builds).
648 C<eval '__PACKAGE__'> now returns the right answer on threaded builds if
649 the current package has been assigned over (as in
650 C<*ThisPackage:: = *ThatPackage::>) [perl #78742].
654 If a package is deleted by code that it calls, it is possible for C<caller>
655 to see a stack frame belonging to that deleted package. C<caller> could
656 crash if the stash's memory address was reused for a scalar and a
657 substitution was performed on the same scalar [perl #113486].
661 C<UNIVERSAL::can> no longer treats its first argument differently
662 depending on whether it is a string or number internally.
666 C<open> with C<< <& >> for the mode checks to see whether the third argument is
667 a number, in determining whether to treat it as a file descriptor or a handle
668 name. Magical variables like C<$1> were always failing the numeric check and
669 being treated as handle names.
673 C<warn>'s handling of magical variables (C<$1>, ties) has undergone several
674 fixes. C<FETCH> is only called once now on a tied argument or a tied C<$@>
675 [perl #97480]. Tied variables returning objects that stringify as "" are
676 no longer ignored. A tied C<$@> that happened to return a reference the
677 I<previous> time is was used is no longer ignored.
681 C<warn ""> now treats C<$@> with a number in it the same way, regardless of
682 whether it happened via C<$@=3> or C<$@="3">. It used to ignore the
683 former. Now it appends "\t...caught", as it has always done with
688 Numeric operators on magical variables (e.g., S<C<$1 + 1>>) used to use
689 floating point operations even where integer operations were more appropriate,
690 resulting in loss of accuracy on 64-bit platforms [perl #109542].
694 Unary negation no longer treats a string as a number if the string happened
695 to be used as a number at some point. So, if C<$x> contains the string "dogs",
696 C<-$x> returns "-dogs" even if C<$y=0+$x> has happened at some point.
700 In Perl 5.14, C<-'-10'> was fixed to return "10", not "+10". But magical
701 variables (C<$1>, ties) were not fixed till now [perl #57706].
705 Unary negation now treats strings consistently, regardless of the internal
710 A regression introduced in Perl v5.16.0 involving
711 C<tr/I<SEARCHLIST>/I<REPLACEMENTLIST>/> has been fixed. Only the first
712 instance is supposed to be meaningful if a character appears more than
713 once in C<I<SEARCHLIST>>. Under some circumstances, the final instance
714 was overriding all earlier ones. [perl #113584]
718 Regular expressions like C<qr/\87/> previously silently inserted a NUL
719 character, thus matching as if it had been written C<qr/\00087/>. Now it
720 matches as if it had been written as C<qr/87/>, with a message that the
721 sequence C<"\8"> is unrecognized.
725 C<__SUB__> now works in special blocks (C<BEGIN>, C<END>, etc.).
729 Thread creation on Windows could theoretically result in a crash if done
730 inside a C<BEGIN> block. It still does not work properly, but it no longer
731 crashes [perl #111610].
735 C<\&{''}> (with the empty string) now autovivifies a stub like any other
736 sub name, and no longer produces the "Unable to create sub" error
741 =head1 Known Problems
747 On VMS, L<Module::Build> still fails its test suite.
751 On Win32, several tests fail intermittently, and may hang unless STDERR is
756 =head1 Acknowledgements
758 Perl 5.17.1 represents approximately 4 weeks of development since Perl 5.17.0
759 and contains approximately 37,000 lines of changes across 710 files from 35
762 Perl continues to flourish into its third decade thanks to a vibrant community
763 of users and developers. The following people are known to have contributed the
764 improvements that became Perl 5.17.1:
766 ?, Andy Dougherty, Aristotle Pagaltzis, Breno G. de Oliveira, Brian Fraser,
767 Chris 'BinGOs' Williams, Craig A. Berry, David Mitchell, Dominic Hargreaves,
768 Evan Miller, Father Chrysostomos, Florian Ragwitz, H.Merijn Brand, Herbert
769 Breunung, Hugo van der Sanden, Jesse Luehrs, Karl Williamson, Karthik
770 Rajagopalan, Lukas Mai, Martin Hasch, Michael Schroeder, Nicholas Clark, Paul
771 Johnson, Reini Urban, Renee Baecker, Rhesa Rozendaal, Ricardo Signes, Shlomi
772 Fish, Steve Hay, Steve Peters, Sullivan Beck, Tony Cook, Volker Schatz, Yves
775 The list above is almost certainly incomplete as it is automatically generated
776 from version control history. In particular, it does not include the names of
777 the (very much appreciated) contributors who reported issues to the Perl bug
780 Many of the changes included in this version originated in the CPAN modules
781 included in Perl's core. We're grateful to the entire CPAN community for
782 helping Perl to flourish.
784 For a more complete list of all of Perl's historical contributors, please see
785 the F<AUTHORS> file in the Perl source distribution.
787 =head1 Reporting Bugs
789 If you find what you think is a bug, you might check the articles
790 recently posted to the comp.lang.perl.misc newsgroup and the perl
791 bug database at http://rt.perl.org/perlbug/ . There may also be
792 information at http://www.perl.org/ , the Perl Home Page.
794 If you believe you have an unreported bug, please run the L<perlbug>
795 program included with your release. Be sure to trim your bug down
796 to a tiny but sufficient test case. Your bug report, along with the
797 output of C<perl -V>, will be sent off to perlbug@perl.org to be
798 analysed by the Perl porting team.
800 If the bug you are reporting has security implications, which make it
801 inappropriate to send to a publicly archived mailing list, then please send
802 it to perl5-security-report@perl.org. This points to a closed subscription
803 unarchived mailing list, which includes
804 all the core committers, who will be able
805 to help assess the impact of issues, figure out a resolution, and help
806 co-ordinate the release of patches to mitigate or fix the problem across all
807 platforms on which Perl is supported. Please only use this address for
808 security issues in the Perl core, not for modules independently
813 The F<Changes> file for an explanation of how to view exhaustive details
816 The F<INSTALL> file for how to build Perl.
818 The F<README> file for general stuff.
820 The F<Artistic> and F<Copying> files for copyright information.