3 perl5120delta - what is new for perl v5.12.0
5 =head1 XXX - THIS DOCUMENT IS ONLY CURRENT THROUGH PERL5114
11 UPDATED MODULE LIST NEEDS TO BE GENERATED
12 ORDERING NEEDS CHECKING
13 HEAVY COPYEDITING IS NEEDED
18 This document describes differences between the 5.10.0 release and
21 Many of the bug fixes in 5.12.0 were already seen in the 5.10.1
22 maintenance release since the two releases were kept closely
23 coordinated (while 5.12.0 was still called 5.11.something).
25 You can see the list of changes in the 5.10.1 release
26 by reading L<perl5101delta>.
28 =head1 Core Enhancements
32 It is now possible to overload the C<qr//> operator, that is,
33 conversion to regexp, like it was already possible to overload
34 conversion to boolean, string or number of objects. It is invoked when
35 an object appears on the right hand side of the C<=~> operator or when
36 it is interpolated into a regexp. See L<overload>.
38 =head2 Pluggable keywords
40 Extension modules can now cleanly hook into the Perl parser to define
41 new kinds of keyword-headed expression and compound statement. The
42 syntax following the keyword is defined entirely by the extension. This
43 allow a completely non-Perl sublanguage to be parsed inline, with the
44 correct ops cleanly generated. This feature is currently considered
47 See L<perlapi/PL_keyword_plugin> for the mechanism. The Perl core
48 source distribution also includes a new module
49 L<XS::APItest::KeywordRPN>, which implements reverse Polish notation
50 arithmetic via pluggable keywords. This module is mainly used for test
51 purposes, and is not normally installed, but also serves as an example
52 of how to use the new mechanism.
54 =head2 APIs for more internals
56 The lowest layers of the lexer and parts of the pad system now have C
57 APIs available to XS extensions. These are necessary to support proper
58 use of pluggable keywords, but have other uses too. The new APIs are
59 experimental, and only cover a small proportion of what would be
60 necessary to take full advantage of the core's facilities in these
61 areas. It is intended that the Perl 5.13 development cycle will see the
62 addition of a full range of clean, supported interfaces.
64 =head2 Overridable function lookup
66 Where an extension module hooks the creation of rv2cv ops to modify the
67 subroutine lookup process, this now works correctly for bareword
68 subroutine calls. This means that prototypes on subroutines referenced
69 this way will be processed correctly. (Previously bareword subroutine
70 names were initially looked up, for parsing purposes, by an unhookable
71 mechanism, so extensions could only properly influence subroutine names
72 that appeared with an C<&> sigil.)
74 =head2 Unicode version
76 Perl is shipped with the latest Unicode version, 5.2, dated October 2009. See
77 L<http://www.unicode.org/versions/Unicode5.2.0> for details about this release
78 of Unicode. See L<perlunicode> for instructions on installing and using
79 older versions of Unicode.
81 =head2 Unicode properties
83 A concerted effort has been made to update Perl to be in sync with the latest
84 Unicode standard. Changes for this include:
86 Perl can now handle every Unicode character property. A new pod,
87 L<perluniprops>, lists all available non-Unihan character properties. By
88 default the Unihan properties and certain others (deprecated and Unicode
89 internal-only ones) are not exposed. See below for more details on
90 these; there is also a section in the pod listing them, and explaining
91 why they are not exposed.
93 Perl now fully supports the Unicode compound-style of using C<=> and C<:>
94 in writing regular expressions: C<\p{property=value}> and
95 C<\p{property:value}> (both of which mean the same thing).
97 Perl now fully supports the Unicode loose matching rules for text
98 between the braces in C<\p{...}> constructs. In addition, Perl allows
99 underscores between digits of numbers.
101 All the Unicode-defined synonyms for properties and property values are
104 C<qr/\X/>, which matches a Unicode logical character, has been expanded to work
105 better with various Asian languages. It now is defined as an I<extended
106 grapheme cluster>. (See L<http://www.unicode.org/reports/tr29/>).
107 Anything matched previously and that made sense will continue to be
108 matched, but in addition:
114 C<\X> will not break apart a C<S<CR LF>> sequence.
118 C<\X> will now match a sequence which includes the C<ZWJ> and C<ZWNJ> characters.
122 C<\X> will now always match at least one character, including an initial mark.
123 Marks generally come after a base character, but it is possible in Unicode to
124 have them in isolation, and C<\X> will now handle that case, for example at the
125 beginning of a line, or after a C<ZWSP>. And this is the part where C<\X>
126 doesn't match the things that it used to that don't make sense. Formerly, for
127 example, you could have the nonsensical case of an accented LF.
131 C<\X> will now match a (Korean) Hangul syllable sequence, and the Thai and Lao
136 Otherwise, this change should be transparent for the non-affected languages.
138 C<\p{...}> matches using the Canonical_Combining_Class property were
139 completely broken in previous Perls. This is now fixed.
141 In previous Perls, the Unicode C<Decomposition_Type=Compat> property and a
142 Perl extension had the same name, which led to neither matching all the
143 correct values (with more than 100 mistakes in one, and several thousand
144 in the other). The Perl extension has now been renamed to be
145 C<Decomposition_Type=Noncanonical> (short: C<dt=noncanon>). It has the same
146 meaning as was previously intended, namely the union of all the
147 non-canonical Decomposition types, with Unicode C<Compat> being just one of
150 C<\p{Uppercase}> and C<\p{Lowercase}> have been brought into line with the
151 Unicode definitions. This means they each match a few more characters
154 C<\p{Cntrl}> now matches the same characters as C<\p{Control}>. This means it
155 no longer will match Private Use (gc=co), Surrogates (gc=cs), nor Format
156 (gc=cf) code points. The Format code points represent the biggest
157 possible problem. All but 36 of them are either officially deprecated
158 or strongly discouraged from being used. Of those 36, likely the most
159 widely used are the soft hyphen (U+00AD), and BOM, ZWSP, ZWNJ, WJ, and
160 similar characters, plus bidirectional controls.
162 C<\p{Alpha}> now matches the same characters as C<\p{Alphabetic}>. The Perl
163 definition included a number of things that aren't really alpha (all
164 marks), while omitting many that were. As a direct consequence, the
165 definitions of C<\p{Alnum}> and C<\p{Word}> which depend on Alpha also change
168 C<\p{Word}> also now doesn't match certain characters it wasn't supposed
169 to, such as fractions.
171 C<\p{Print}> no longer matches the line control characters: Tab, LF, CR,
172 FF, VT, and NEL. This brings it in line with standards and the documentation.
174 C<\p{Decomposition_Type=Canonical}> now includes the Hangul syllables.
176 C<\p{XDigit}> now matches the same characters as C<\p{Hex_Digit}>. This
177 means that in addition to the characters it currently matches,
178 C<[A-Fa-f0-9]>, it will also match the 22 fullwidth equivalents, for
179 example U+FF10: FULLWIDTH DIGIT ZERO.
181 The Numeric type property has been extended to include the Unihan
184 There is a new Perl extension, the 'Present_In', or simply 'In',
185 property. This is an extension of the Unicode Age property, but
186 C<\p{In=5.0}> matches any code point whose usage has been determined
187 I<as of> Unicode version 5.0. The C<\p{Age=5.0}> only matches code points
188 added in I<precisely> version 5.0.
190 A number of properties did not have the correct values for unassigned
191 code points. This is now fixed. The affected properties are
192 Bidi_Class, East_Asian_Width, Joining_Type, Decomposition_Type,
193 Hangul_Syllable_Type, Numeric_Type, and Line_Break.
195 The Default_Ignorable_Code_Point, ID_Continue, and ID_Start properties
196 have been updated to their current Unicode definitions.
198 Certain properties that are supposed to be Unicode internal-only were
199 erroneously exposed by previous Perls. Use of these in regular
200 expressions will now generate, if enabled, a deprecated warning message.
201 The properties are: Other_Alphabetic, Other_Default_Ignorable_Code_Point,
202 Other_Grapheme_Extend, Other_ID_Continue, Other_ID_Start, Other_Lowercase,
203 Other_Math, and Other_Uppercase.
205 An installation can now fairly easily change which Unicode properties
206 Perl understands. As mentioned above, certain properties are by default
207 turned off. These include all the Unihan properties (which should be
208 accessible via the CPAN module Unicode::Unihan) and any deprecated or
209 Unicode internal-only property that Perl has never exposed.
211 The generated files in the C<lib/unicore/To> directory are now more
212 clearly marked as being stable, directly usable by applications.
213 New hash entries in them give the format of the normal entries,
214 which allows for easier machine parsing. Perl can generate files
215 in this directory for any property, though most are suppressed. An
216 installation can choose to change which get written. Instructions
217 are in L<perluniprops>.
219 =head2 Regular Expressions
221 U+0FFFF is now a legal character in regular expressions.
223 =head2 A proper interface for pluggable Method Resolution Orders
225 As of Perl 5.11.0 there is a new interface for plugging and using method
226 resolution orders other than the default (linear depth first search).
227 The C3 method resolution order added in 5.10.0 has been re-implemented as
228 a plugin, without changing its Perl-space interface. See L<perlmroapi> for
231 =head2 The C<overloading> pragma
233 This pragma allows you to lexically disable or enable overloading
234 for some or all operations. (Yuval Kogman)
236 =head2 C<\N> experimental regex escape
238 A new regex escape has been added, C<\N>. It will match any character that
239 is not a newline, independently from the presence or absence of the single
240 line match modifier C</s>. It is not usable within a character class.
241 C<\N{3}> means to match 3 non-newlines; C<\N{5,}> means to match at least 5.
242 C<\N{NAME}> still means the character or sequence named C<NAME>, but C<NAME> no
243 longer can be things like C<3>, or C<5,>.
244 Compatibility with Unicode names is preserved, as none look like these, but it
245 has been possible to create custom names that do look like them, and those will
246 no longer work. (Rafael Garcia-Suarez)
248 This will break a L<custom charnames translator|charnames/CUSTOM TRANSLATORS>
249 which allows numbers for character names, as C<\N{3}> will now mean to match 3
250 non-newline characters, and not the character whose name is C<3>. (No standard
251 name is a number, so only a custom translator would be affected.)
253 This escape is experimental, subject to change, because there is some concern
254 about possible confusion with the previous meaning of C<\N{...}>
256 =head2 Implicit strictures
258 Using the C<use VERSION> syntax with a version number greater or equal
259 to 5.11.0 will also lexically enable strictures just like C<use strict>
260 would do (in addition to enabling features.) So, the following:
269 =head2 Parallel tests
271 The core distribution can now run its regression tests in parallel on
272 Unix-like platforms. Instead of running C<make test>, set C<TEST_JOBS> in
273 your environment to the number of tests to run in parallel, and run
274 C<make test_harness>. On a Bourne-like shell, this can be done as
276 TEST_JOBS=3 make test_harness # Run 3 tests in parallel
278 An environment variable is used, rather than parallel make itself, because
279 L<TAP::Harness> needs to be able to schedule individual non-conflicting test
280 scripts itself, and there is no standard interface to C<make> utilities to
281 interact with their job schedulers.
283 Note that currently some test scripts may fail when run in parallel (most
284 notably C<ext/IO/t/io_dir.t>). If necessary run just the failing scripts
285 again sequentially and see if the failures go away.
287 =head2 The C<...> operator
289 A new operator, C<...>, nicknamed the Yada Yada operator, has been added.
290 It is intended to mark placeholder code that is not yet implemented.
291 See L<perlop/"Yada Yada Operator">. (chromatic)
293 =head2 DTrace support
295 Some support for DTrace has been added. See "DTrace support" in F<INSTALL>.
297 =head2 Support for C<configure_requires> in CPAN module metadata
299 Both C<CPAN> and C<CPANPLUS> now support the C<configure_requires> keyword
300 in the F<META.yml> metadata file included in most recent CPAN distributions.
301 This allows distribution authors to specify configuration prerequisites that
302 must be installed before running F<Makefile.PL> or F<Build.PL>.
304 See the documentation for C<ExtUtils::MakeMaker> or C<Module::Build> for more
305 on how to specify C<configure_requires> when creating a distribution for CPAN.
307 =head2 C<each> is now more flexible
309 The C<each> function can now operate on arrays.
311 =head2 Y2038 compliance
313 Perl's core time-related functions are now Y2038 compliant. (With 29
316 =head2 C<$,> flexibility
318 The variable C<$,> may now be tied.
320 =head2 // in where clauses
322 // now behaves like || in when clauses
324 =head2 Enabling warnings from your shell environment
326 You can now set C<-W> from the C<PERL5OPT> environment variable
328 =head2 C<delete local>
330 C<delete local> now allows you to locally delete a hash entry.
332 =head2 New support for Abstract namespace sockets
334 Abstract namespace sockets are Linux-specific socket type that live in
335 AF_UNIX family, slightly abusing it to be able to use arbitrary
336 character arrays as addresses: They start with nul byte and are not
337 terminated by nul byte, but with the length passed to the socket()
340 =head2 New C<package NAME VERSION> syntax
342 This new syntax allows a module author to set the $VERSION of a namespace
343 when the namespace is declared with 'package'. It eliminates the need
344 for C<our $VERSION = ...> and similar constructs. E.g.
346 package Foo::Bar 1.23;
347 # $Foo::Bar::VERSION == 1.23
349 There are several advantages to this:
355 C<$VERSION> is parsed in exactly the same way as C<use NAME VERSION>
359 C<$VERSION> is set at compile time
363 C<$VERSION> is a version object that provides proper overloading of
364 comparision operators so comparing C<$VERSION> to decimal (1.23) or
365 dotted-decimal (v1.2.3) version numbers works correctly.
369 Eliminates C<$VERSION = ...> and C<eval $VERSION> clutter
373 As it requires VERSION to be a numeric literal or v-string
374 literal, it can be statically parsed by toolchain modules
375 without C<eval> the way MM-E<gt>parse_version does for C<$VERSION = ...>
379 It does not break old code with only C<package NAME>, but code that uses
380 C<package NAME VERSION> will need to be restricted to perl 5.12.0 or newer
381 This is analogous to the change to C<open> from two-args to three-args.
382 Users requiring the latest Perl will benefit, and perhaps after several
383 years, it will become a standard practice.
387 However, C<package NAME VERSION> requires a new, 'strict' version
388 number format. See L<"Version number formats"> for details.
390 =head1 Incompatible Changes
392 =head2 Version number formats
394 Acceptable version number formats have been formalized into "strict" and
395 "lax" rules. C<package NAME VERSION> takes a strict version number.
396 C<UNIVERSAL::VERSION> and the L<version> object constructors take lax
397 version numbers. Providing an invalid version will result in a fatal
398 error. The version argument in C<use NAME VERSION> is first parsed as a
399 numeric literal or v-string and then passed to C<UNIVERSAL::VERSION>
400 (and must then pass the "lax" format test).
402 These formats are documented fully in the L<version> module. To a first
403 approximation, a "strict" version number is a positive decimal number
404 (integer or decimal-fraction) without exponentiation or else a
405 dotted-decimal v-string with a leading 'v' character and at least three
406 components. A "lax" version number allows v-strings with fewer than
407 three components or without a leading 'v'. Under "lax" rules, both
408 decimal and dotted-decimal versions may have a trailing "alpha"
409 component separated by an underscore character after a fractional or
410 dotted-decimal component.
412 The L<version> module adds C<version::is_strict> and C<version::is_lax>
413 functions to check a scalar against these rules.
415 =head2 @INC reorganization
417 In @INC, ARCHLIB and PRIVLIB now occur after after the current version's
418 site_perl and vendor_perl.
420 =head2 Switch statement changes
422 The handling of complex expressions by the C<given>/C<when> switch
423 statement has been enhanced. These enhancements are also available in
424 5.10.1 and subsequent 5.10 releases. There are two new cases where
425 C<when> now interprets its argument as a boolean, instead of an
426 expression to be used in a smart match:
428 =head2 flip-flop operators
430 The C<..> and C<...> flip-flop operators are now evaluated in boolean
431 context, following their usual semantics; see L<perlop/"Range Operators">.
433 Note that, as in perl 5.10.0, C<when (1..10)> will not work to test
434 whether a given value is an integer between 1 and 10; you should use
435 C<when ([1..10])> instead (note the array reference).
437 However, contrary to 5.10.0, evaluating the flip-flop operators in boolean
438 context ensures it can now be useful in a C<when()>, notably for
439 implementing bistable conditions, like in:
441 when (/^=begin/ .. /^=end/) {
445 =head2 defined-or operator
447 A compound expression involving the defined-or operator, as in
448 C<when (expr1 // expr2)>, will be treated as boolean if the first
449 expression is boolean. (This just extends the existing rule that applies
450 to the regular or operator, as in C<when (expr1 || expr2)>.)
452 =head2 Smart match changes
454 This section details more changes brought to the semantics to
455 the smart match operator, that naturally also modify the behaviour
456 of the switch statements where smart matching is implicitly used.
457 These changes were also made for the 5.10.1 release, and will remain in
458 subsequent 5.10 releases.
460 =head3 Changes to type-based dispatch
462 The smart match operator C<~~> is no longer commutative. The behaviour of
463 a smart match now depends primarily on the type of its right hand
464 argument. Moreover, its semantics have been adjusted for greater
465 consistency or usefulness in several cases. While the general backwards
466 compatibility is maintained, several changes must be noted:
472 Code references with an empty prototype are no longer treated specially.
473 They are passed an argument like the other code references (even if they
474 choose to ignore it).
478 C<%hash ~~ sub {}> and C<@array ~~ sub {}> now test that the subroutine
479 returns a true value for each key of the hash (or element of the
480 array), instead of passing the whole hash or array as a reference to
485 Due to the commutativity breakage, code references are no longer
486 treated specially when appearing on the left of the C<~~> operator,
487 but like any vulgar scalar.
491 C<undef ~~ %hash> is always false (since C<undef> can't be a key in a
492 hash). No implicit conversion to C<""> is done (as was the case in perl
497 C<$scalar ~~ @array> now always distributes the smart match across the
498 elements of the array. It's true if one element in @array verifies
499 C<$scalar ~~ $element>. This is a generalization of the old behaviour
500 that tested whether the array contained the scalar.
504 The full dispatch table for the smart match operator is given in
505 L<perlsyn/"Smart matching in detail">.
507 =head3 Smart match and overloading
509 According to the rule of dispatch based on the rightmost argument type,
510 when an object overloading C<~~> appears on the right side of the
511 operator, the overload routine will always be called (with a 3rd argument
512 set to a true value, see L<overload>.) However, when the object will
513 appear on the left, the overload routine will be called only when the
514 rightmost argument is a simple scalar. This way, distributivity of smart
515 match across arrays is not broken, as well as the other behaviours with
516 complex types (coderefs, hashes, regexes). Thus, writers of overloading
517 routines for smart match mostly need to worry only with comparing
518 against a scalar, and possibly with stringification overloading; the
519 other common cases will be automatically handled consistently.
521 C<~~> will now refuse to work on objects that do not overload it (in order
522 to avoid relying on the object's underlying structure). (However, if the
523 object overloads the stringification or the numification operators, and
524 if overload fallback is active, it will be used instead, as usual.)
526 =head2 Labels can't be keywords
528 Labels used as targets for the C<goto>, C<last>, C<next> or C<redo>
529 statements cannot be keywords anymore. This restriction will prevent
530 potential confusion between the C<goto LABEL> and C<goto EXPR> syntaxes:
531 for example, a statement like C<goto print> would jump to a label whose
532 name would be the return value of C<print()>, (usually 1), instead of a
533 label named C<print>. Moreover, the other control flow statements
534 would just ignore any keyword passed to them as a label name. Since
535 such labels cannot be defined anymore, this kind of error will be
538 =head2 Other incompatible changes
544 The definitions of a number of Unicode properties have changed to match those
545 of the current Unicode standard. These are listed above under L</Unicode
546 properties>. This could break code that is expecting the old definitions.
550 The boolkeys op moved to the group of hash ops. This breaks binary
555 Filehandles are blessed directly into C<IO::Handle>, as C<FileHandle> is
556 merely a wrapper around C<IO::Handle>.
558 The previous behaviour was to bless Filehandles into L<FileHandle>
559 (an empty proxy class) if it was loaded into memory and otherwise
560 to bless them into C<IO::Handle>.
564 The semantics of C<use feature :5.10*> have changed slightly.
565 See L<"Modules and Pragmata"> for more information.
569 The version control system used for the development of the perl
570 interpreter has been switched from Perforce to git. This is mainly an
571 internal issue that only affects people actively working on the perl core;
572 but it may have minor external visibility, for example in some of details
573 of the output of C<perl -V>. See L<perlrepository> for more information.
577 The internal structure of the C<ext/> directory in the perl source has
578 been reorganised. In general, a module C<Foo::Bar> whose source was
579 stored under F<ext/Foo/Bar/> is now located under F<ext/Foo-Bar/>. Also,
580 nearly all dual-life modules have been moved from F<lib/> to F<ext/>. This
581 is purely a source tarball change, and should make no difference to the
582 compilation or installation of perl, unless you have a very customised build
583 process that explicitly relies on this structure, or which hard-codes the
584 C<nonxs_ext> F<Configure> parameter. Specifically, this change does not by
585 default alter the location of any files in the final installation.
589 As part of the C<Test::Harness> 2.x to 3.x upgrade, the experimental
590 C<Test::Harness::Straps> module has been removed.
591 See L</"Updated Modules"> for more details.
595 As part of the C<ExtUtils::MakeMaker> upgrade, the
596 C<ExtUtils::MakeMaker::bytes> and C<ExtUtils::MakeMaker::vmsish> modules
597 have been removed from this distribution.
601 C<Module::CoreList> no longer contains the C<%:patchlevel> hash.
605 This one is actually a change introduced in 5.10.0, but it was missed
606 from that release's perldelta, so it is mentioned here instead.
608 A bugfix related to the handling of the C</m> modifier and C<qr> resulted
609 in a change of behaviour between 5.8.x and 5.10.0:
611 # matches in 5.8.x, doesn't match in 5.10.0
612 $re = qr/^bar/; "foo\nbar" =~ /$re/m;
616 C<length undef> now returns undef.
620 Unsupported private C API functions are now declared "static" to prevent
621 leakage to Perl's public API.
625 To support the bootstrapping process, F<miniperl> no longer builds with
626 UTF-8 support in the regexp engine.
628 This allows a build to complete with PERL_UNICODE set and a UTF-8 locale.
629 Without this there's a bootstrapping problem, as miniperl can't load the UTF-8
630 components of the regexp engine, because they're not yet built.
634 F<miniperl>'s @INC is now restricted to just C<-I...>, the split of
635 C<$ENV{PERL5LIB}>, and "C<.>"
639 A space or a newline is now required after a C<"#line XXX"> directive.
643 Tied filehandles now have an additional method EOF which provides the EOF type
647 To better match all other flow control statements, C<foreach> may no
648 longer be used as an attribute.
654 From time to time, Perl's developers find it necessary to deprecate
655 features or modules we've previously shipped as part of the core
656 distribution. We are well aware of the pain and frustration that a
657 backwards-incompatible change to Perl can cause for developers building
658 or maintaining software in Perl. You can be sure that when we deprecate
659 a functionality or syntax, it isn't a choice we make lightly. Sometimes,
660 we choose to deprecate functionality or syntax because it was found to
661 be poorly designed or implemented. Sometimes, this is because they're
662 holding back other features or causing performance problems. Sometimes,
663 the reasons are more complex. Wherever possible, we try to keep deprecated
664 functionality available to developers in its previous form for at least
665 one major release. So long as a deprecated feature isn't actively
666 disrupting our ability to maintain and extend Perl, we'll try to leave
667 it in place as long as possible.
669 The following items are now deprecated.
673 =item Use of C<:=> to mean an empty attribute list is now deprecated.
675 An accident of Perl's parser meant that these constructions were all
682 with the C<:> being treated as the start of an attribute list, which
683 ends before the C<=>. As whitespace is not significant here, all are
684 parsed as an empty attribute list, hence all the above are equivalent
685 to, and better written as
689 because no attribute processing is done for an empty list.
691 As is, this meant that C<:=> cannot be used as a new token, without
692 silently changing the meaning of existing code. Hence that particular
693 form is now deprecated, and will become a syntax error. If it is
694 absolutely necessary to have empty attribute lists (for example,
695 because of a code generator) then avoid the warning by adding a space
698 =item C<< UNIVERSAL->import() >>
700 The method C<< UNIVERSAL->import() >> is now deprecated. Attempting to
701 pass import arguments to a C<use UNIVERSAL> statement will result in a
704 =item Use of "goto" to jump into a construct is deprecated
706 Using C<goto> to jump from an outer scope into an inner scope is now
707 deprecated. This rare use case was causing problems in the
708 implementation of scopes.
710 =item Custom character names in \N{name} should look like names
712 In C<\N{I<name>}>, I<name> can be just about anything. The standard Unicode
713 names have a very limited domain, but a custom name translator could create
714 names that are, for example, made up entirely of punctuation symbols. It is
715 now deprecated to make names that don't begin with an alphabetic character, and
716 aren't alphanumeric or contain other than a very few other characters,
717 namely spaces, dashes, parentheses and colons. Because of the added meaning of
718 C<\N> (See L</C<\N> experimental regex escape>), names that look like curly
719 brace -enclosed quantifiers won't work. For example, C<\N{3,4}> now means to
720 match 3 to 4 non-newlines; before a custom name C<3,4> could have been created.
722 =item Deprecated Modules
724 The following modules will be removed from the core distribution in a future
725 release, and should be installed from CPAN instead. Distributions on CPAN
726 which require these should add them to their prerequisites. The core versions
727 of these modules warnings will issue a deprecation warning.
729 If you ship a packaged version of Perl, either alone or as part of a larger
730 system, then you should carefully consider the reprecussions of core module
731 deprecations. You may want to consider shipping your default build of
732 Perl with packages for some or all deprecated modules which install into
733 C<vendor> or C<site> perl library directories. This will inhibit the
734 deprecation warnings.
736 Alternatively, you may want to consider patching F<lib/deprecate.pm>
737 to provide deprecation warnings specific to your packaging system or
738 distribution of Perl.
744 =item L<Pod::Plainer>
750 Switch is buggy and should be avoided. See L<perlsyn/"Switch
751 statements"> for its replacement.
757 C<suidperl> has been removed. It used to provide a mechanism to
758 emulate setuid permission bits on systems that don't support it properly.
760 =item Assignment to $[
764 Remove attrs, which has been deprecated since 1999-10-02.
766 =item Use of the attribute :locked on subroutines.
768 =item Use of "locked" with the attributes pragma.
770 =item Use of "unique" with the attributes pragma.
772 =item Numerous Perl 4-era libraries:
774 F<termcap.pl>, F<tainted.pl>, F<stat.pl>, F<shellwords.pl>, F<pwd.pl>,
775 F<open3.pl>, F<open2.pl>, F<newgetopt.pl>, F<look.pl>, F<find.pl>,
776 F<finddepth.pl>, F<importenv.pl>, F<hostname.pl>, F<getopts.pl>,
777 F<getopt.pl>, F<getcwd.pl>, F<flush.pl>, F<fastcwd.pl>, F<exceptions.pl>,
778 F<ctime.pl>, F<complete.pl>, F<cacheout.pl>, F<bigrat.pl>, F<bigint.pl>,
779 F<bigfloat.pl>, F<assert.pl>, F<abbrev.pl>, F<dotsh.pl>, and
780 F<timelocal.pl> are all now deprecated. Using them will incur a warning.
784 =head1 Modules and Pragmata
786 =head2 Dual-lifed modules moved
788 Dual-lifed modules maintained primarily in the Perl core now live in dist/.
789 Dual-lifed modules maintained primarily on CPAN now live in cpan/
791 In previous releases of Perl, it was customary to enumerate all module
792 changes in this section of the C<perldelta> file. From 5.11.0 forward
793 only notable updates (such as new or deprecated modules ) will be listed
794 in this section. For a complete reference to the versions of modules
795 shipped in a given release of perl, please see L<Module::CoreList>.
797 =head2 New Modules and Pragmata
805 This is a new lexically-scoped alternative for the C<Fatal> module.
806 The bundled version is 2.06_01. Note that in this release, using a string
807 eval when C<autodie> is in effect can cause the autodie behaviour to leak
808 into the surrounding scope. See L<autodie/"BUGS"> for more details.
812 C<Compress::Raw::Bzip2>
814 This has been added to the core (version 2.020).
820 This pragma establishes an ISA relationship with base classes at compile
821 time. It provides the key feature of C<base> without further unwanted
828 This has been added to the core (version 1.39).
832 =head2 Pragmata Changes
840 See L</"The C<overloading> pragma"> above.
846 The C<attrs> pragma has been removed. It had been marked as deprecated since
853 The Unicode F<NameAliases.txt> database file has been added. This has the
854 effect of adding some extra C<\N> character names that formerly wouldn't
855 have been recognised; for example, C<"\N{LATIN CAPITAL LETTER GHA}">.
861 The meaning of the C<:5.10> and C<:5.10.X> feature bundles has
862 changed slightly. The last component, if any (i.e. C<X>) is simply ignored.
863 This is predicated on the assumption that new features will not, in
864 general, be added to maintenance releases. So C<:5.10> and C<:5.10.X>
865 have identical effect. This is a change to the behaviour documented for
872 Upgraded from version 1.00 to 1.01. Performance for single inheritance is 40%
873 faster - see L</"Performance Enhancements"> below.
875 C<mro> is now implemented as an XS extension. The documented interface has not
876 changed. Code relying on the implementation detail that some C<mro::>
877 methods happened to be available at all times gets to "keep both pieces".
883 Supports %.0f formatting internally.
889 Allow overloading of 'qr'.
895 Upgraded from version 1.19 to 1.20.
901 This pragma no longer suppresses C<Use of uninitialized value in range
902 (or flip)> warnings. [perl #71204]
908 Upgraded from 1.13 to 1.14. Added the C<unicode_strings> feature:
910 use feature "unicode_strings";
912 This pragma turns on Unicode semantics for the case-changing operations
913 (C<uc>, C<lc>, C<ucfirst>, C<lcfirst>) on strings that don't have the
914 internal UTF-8 flag set, but that contain single-byte characters between
921 Upgraded from version 1.74 to 1.75.
927 Upgraded from version 0.02 to 0.03.
929 This version introduces the C<stash_name> method to allow subclasses of
930 C<less> to pick where in %^H to store their stash.
936 Upgraded from version 0.77 to 0.81.
938 This version adds support for L</Version number formats> as described earlier
939 in this document and in its own documentation.
945 Upgraded from 1.07 to 1.09.
947 Added new C<warnings::fatal_enabled()> function.
948 This version adds the C<illegalproto> warning category. See also L</New or
949 Changed Diagnostics> for this change.
954 =head2 Updated Modules
958 =item XXX TODO RECALCULATE THIS VS 5.10.0
962 =head2 Removed Modules and Pragmata
970 Removed from the Perl core. Prior version was 'undef'.
976 =head2 New Documentation
984 This contains instructions on how to build perl for the Haiku platform.
990 This describes the new interface for pluggable Method Resolution Orders.
996 This document, by Richard Foley, provides an introduction to the use of
997 performance and optimization techniques which can be used with particular
998 reference to perl programs.
1004 This describes how to access the perl source using the I<git> version
1009 L<perlpolicy> extends the "Social contract about contributed modules" into
1010 the beginnings of a document on Perl porting policies.
1014 =head2 Changes to Existing Documentation
1016 The various large F<Changes*> files (which listed every change made to perl
1017 over the last 18 years) have been removed, and replaced by a small file,
1018 also called F<Changes>, which just explains how that same information may
1019 be extracted from the git version control system.
1021 The file F<Porting/patching.pod> has been deleted, as it mainly described
1022 interacting with the old Perforce-based repository, which is now obsolete.
1023 Information still relevant has been moved to L<perlrepository>.
1025 L<perlapi>, L<perlintern>, L<perlmodlib> and L<perltoc> are now all
1026 generated at build time, rather than being shipped as part of the release.
1032 Documented -X overloading.
1036 Documented that C<when()> treats specially most of the filetest operators
1040 Documented C<when> as a syntax modifier
1044 Eliminated "Old Perl threads tutorial", which described 5005 threads.
1046 F<pod/perlthrtut.pod> is the same material reworked for ithreads.
1050 Correct previous documentation: v-strings are not deprecated
1052 With version objects, we need them to use MODULE VERSION syntax. This
1053 patch removes the deprecation notice.
1057 Added security contact information to L<perlsec>
1059 A significant fraction of the core documentation has been updated to clarify
1060 the behavior of Perl's Unicode handling.
1062 Much of the remaining core documentation has been reviewed and edited
1063 for clarity, consistent use of language, and to fix the spelling of Tom
1064 Christiansen's name.
1066 The Pod specification (L<perlpodspec>) has been updated to bring the
1067 specification in line with modern usage already supported by most Pod
1068 systems. A parameter string may now follow the format name in a
1069 "begin/end" region. Links to URIs with a text description are now
1070 allowed. The usage of C<LE<lt>"section"E<gt>> has been marked as
1073 L<if.pm|if> has been documented in L<perlfunc/use> as a means to get
1074 conditional loading of modules despite the implicit BEGIN block around
1079 The documentation for C<$1> in perlvar.pod has been clarified.
1083 =head1 Performance Enhancements
1089 A new internal cache means that C<isa()> will often be faster.
1093 The implementation of C<C3> Method Resolution Order has been optimised -
1094 linearisation for classes with single inheritance is 40% faster. Performance
1095 for multiple inheritance is unchanged.
1099 Under C<use locale>, the locale-relevant information is now cached on
1100 read-only values, such as the list returned by C<keys %hash>. This makes
1101 operations such as C<sort keys %hash> in the scope of C<use locale> much
1106 Empty C<DESTROY> methods are no longer called.
1110 Faster C<Perl_sv_utf8_upgrade()>
1114 Speed up C<keys> on empty hash
1118 C<if (%foo)> has been optimized to be faster than C<if (keys %foo)>
1122 Reversing an array to itself (as in C<@a = reverse @a>) in void context
1123 now happens in-place and is several orders of magnitude faster than it
1124 used to be. It will also preserve non-existent elements whenever
1125 possible, i.e. for non magical arrays or tied arrays with C<EXISTS> and
1130 =head1 Installation and Configuration Improvements
1132 =head2 F<ext/> reorganisation
1134 The layout of directories in F<ext> has been revised. Specifically, all
1135 extensions are now flat, and at the top level, with C</> in pathnames
1136 replaced by C<->, so that F<ext/Data/Dumper/> is now F<ext/Data-Dumper/>,
1137 etc. The names of the extensions as specified to F<Configure>, and as
1138 reported by C<%Config::Config> under the keys C<dynamic_ext>,
1139 C<known_extensions>, C<nonxs_ext> and C<static_ext> have not changed, and
1140 still use C</>. Hence this change will not have any affect once perl is
1141 installed. C<Safe> has been split out from being part of C<Opcode>, and
1142 C<mro> is now an extension in its own right.
1144 Nearly all dual-life modules have been moved from F<lib> to F<ext>, and will
1145 now appear as known C<nonxs_ext>. This will made no difference to the
1146 structure of an installed perl, nor will the modules installed differ,
1147 unless you run F<Configure> with options to specify an exact list of
1148 extensions to build. In this case, you will rapidly become aware that you
1149 need to add to your list, because various modules needed to complete the
1150 build, such as C<ExtUtils::ParseXS>, have now become extensions, and
1151 without them the build will fail well before it attempts to run the
1154 =head2 Configuration improvements
1156 If C<vendorlib> and C<vendorarch> are the same, then they are only added to
1159 C<$Config{usedevel}> and the C-level C<PERL_USE_DEVEL> are now defined if
1160 perl is built with C<-Dusedevel>.
1162 F<Configure> will enable use of C<-fstack-protector>, to provide protection
1163 against stack-smashing attacks, if the compiler supports it.
1165 F<Configure> will now determine the correct prototypes for re-entrant
1166 functions and for C<gconvert> if you are using a C++ compiler rather
1169 On Unix, if you build from a tree containing a git repository, the
1170 configuration process will note the commit hash you have checked out, for
1171 display in the output of C<perl -v> and C<perl -V>. Unpushed local commits
1172 are automatically added to the list of local patches displayed by
1175 USE_ATTRIBUTES_FOR_PERLIO is now reported in the compile-time options
1176 listed by the C<-V> switch.
1178 =head2 Compilation improvements
1180 As part of the flattening of F<ext>, all extensions on all platforms are
1181 built by F<make_ext.pl>. This replaces the Unix-specific
1182 F<ext/util/make_ext>, VMS-specific F<make_ext.com> and Win32-specific
1183 F<win32/buildext.pl>.
1185 =head1 Changed Internals
1191 C<Perl_pmflag> has been removed from the public API. Calling it now
1192 generates a deprecation warning, and it will be removed in a future
1193 release. Although listed as part of the API, it was never documented,
1194 and only ever used in F<toke.c>, and prior to 5.10, F<regcomp.c>. In
1195 core, it has been replaced by a static function.
1199 Perl_magic_setmglob now knows about globs, fixing RT #71254.
1203 TODO: C<SVt_RV> is gone. RVs are now stored in IVs
1207 TODO: REGEXPs are first class
1211 TODO: OOK is reworked, such that an OOKed scalar is PV not PVIV
1215 The J.R.R. Tolkien quotes at the head of C source file have been checked and
1216 proper citations added, thanks to a patch from Tom Christiansen.
1220 C<Perl_vcroak()> now accepts a null first argument. In addition, a full audit
1221 was made of the "not NULL" compiler annotations, and those for several
1222 other internal functions were corrected.
1226 New macros C<dSAVEDERRNO>, C<dSAVE_ERRNO>, C<SAVE_ERRNO>, C<RESTORE_ERRNO>
1227 have been added to formalise the temporary saving of the C<errno>
1232 The function C<Perl_sv_insert_flags> has been added to augment
1237 The function C<Perl_newSV_type(type)> has been added, equivalent to
1238 C<Perl_newSV()> followed by C<Perl_sv_upgrade(type)>.
1242 The function C<Perl_newSVpvn_flags()> has been added, equivalent to
1243 C<Perl_newSVpvn()> and then performing the action relevant to the flag.
1245 Two flag bits are currently supported.
1253 This will call C<SvUTF8_on()> for you. (Note that this does not convert an
1254 sequence of ISO 8859-1 characters to UTF-8). A wrapper, C<newSVpvn_utf8()>
1255 is available for this.
1261 Call C<Perl_sv_2mortal()> on the new SV.
1265 There is also a wrapper that takes constant strings, C<newSVpvs_flags()>.
1269 The function C<Perl_croak_xs_usage> has been added as a wrapper to
1274 The functions C<PerlIO_find_layer> and C<PerlIO_list_alloc> are now
1279 C<PL_na> has been exterminated from the core code, replaced by local STRLEN
1280 temporaries, or C<*_nolen()> calls. Either approach is faster than C<PL_na>,
1281 which is a pointer dereference into the interpreter structure under ithreads,
1282 and a global variable otherwise.
1286 C<Perl_mg_free()> used to leave freed memory accessible via C<SvMAGIC()> on
1287 the scalar. It now updates the linked list to remove each piece of magic
1292 Under ithreads, the regex in C<PL_reg_curpm> is now reference counted. This
1293 eliminates a lot of hackish workarounds to cope with it not being reference
1298 C<Perl_mg_magical()> would sometimes incorrectly turn on C<SvRMAGICAL()>.
1299 This has been fixed.
1303 The I<public> IV and NV flags are now not set if the string value has
1304 trailing "garbage". This behaviour is consistent with not setting the
1305 public IV or NV flags if the value is out of range for the type.
1309 SV allocation tracing has been added to the diagnostics enabled by C<-Dm>.
1310 The tracing can alternatively output via the C<PERL_MEM_LOG> mechanism, if
1311 that was enabled when the F<perl> binary was compiled.
1315 Smartmatch resolution tracing has been added as a new diagnostic. Use C<-DM> to
1320 A new debugging flag C<-DB> now dumps subroutine definitions, leaving
1321 C<-Dx> for its original purpose of dumping syntax trees.
1325 Uses of C<Nullav>, C<Nullcv>, C<Nullhv>, C<Nullop>, C<Nullsv> etc have been
1326 replaced by C<NULL> in the core code, and non-dual-life modules, as C<NULL>
1327 is clearer to those unfamiliar with the core code.
1331 A macro C<MUTABLE_PTR(p)> has been added, which on (non-pedantic) gcc will
1332 not cast away C<const>, returning a C<void *>. Macros C<MUTABLE_SV(av)>,
1333 C<MUTABLE_SV(cv)> etc build on this, casting to C<AV *> etc without
1334 casting away C<const>. This allows proper compile-time auditing of
1335 C<const> correctness in the core, and helped picked up some errors (now
1340 Macros C<mPUSHs()> and C<mXPUSHs()> have been added, for pushing SVs on the
1341 stack and mortalizing them.
1345 Use of the private structure C<mro_meta> has changed slightly. Nothing
1346 outside the core should be accessing this directly anyway.
1350 A new tool, F<Porting/expand-macro.pl> has been added, that allows you
1351 to view how a C preprocessor macro would be expanded when compiled.
1352 This is handy when trying to decode the macro hell that is the perl
1361 Many modules updated from CPAN incorporate new tests.
1362 Several tests that have the potential to hang forever if they fail now
1363 incorporate a "watchdog" functionality that will kill them after a timeout,
1364 which helps ensure that C<make test> and C<make test_harness> run to
1365 completion automatically. (Jerry Hedden).
1367 Some core-specific tests have been added:
1373 Significant cleanups to core tests to ensure that language and
1374 interpreter features are not used before they're tested.
1378 C<make test_porting> now runs a number of important pre-commit checks
1379 which might be of use to anyone working on the Perl core.
1383 F<t/porting/podcheck.t> automatically checks the well-formedness of
1384 POD found in all .pl, .pm and .pod files in the F<MANIFEST>, other than in
1385 dual-lifed modules which are primarily maintained outside the Perl core.
1389 F<t/porting/manifest.t> now tests that all files listed in MANIFEST are present.
1393 F<t/op/while_readdir.t>
1395 Test that a bare readdir in while loop sets $_.
1399 F<t/comp/retainedlines.t>
1401 Check that the debugger can retain source lines from C<eval>.
1405 F<t/io/perlio_fail.t>
1407 Check that bad layers fail.
1411 F<t/io/perlio_leaks.t>
1413 Check that PerlIO layers are not leaking.
1417 F<t/io/perlio_open.t>
1419 Check that certain special forms of open work.
1425 General PerlIO tests.
1431 Check that there is no unexpected interaction between the internal types
1432 C<PVBM> and C<PVGV>.
1436 F<t/mro/package_aliases.t>
1438 Check that mro works properly in the presence of aliased packages.
1444 Tests for C<dbmopen> and C<dbmclose>.
1450 Tests for the interaction of C<index> and threads.
1456 Tests for the interaction of esoteric patterns and threads.
1462 Test that C<qr> doesn't leak.
1466 F<t/op/reg_email_thr.t>
1468 Tests for the interaction of regex recursion and threads.
1472 F<t/op/regexp_qr_embed_thr.t>
1474 Tests for the interaction of patterns with embedded C<qr//> and threads.
1478 F<t/op/regexp_unicode_prop.t>
1480 Tests for Unicode properties in regular expressions.
1484 F<t/op/regexp_unicode_prop_thr.t>
1486 Tests for the interaction of Unicode properties and threads.
1490 F<t/op/reg_nc_tie.t>
1492 Test the tied methods of C<Tie::Hash::NamedCapture>.
1496 F<t/op/reg_posixcc.t>
1498 Check that POSIX character classes behave consistently.
1504 Check that exportable C<re> functions in F<universal.c> work.
1508 F<t/op/setpgrpstack.t>
1510 Check that C<setpgrp> works.
1514 F<t/op/substr_thr.t>
1516 Tests for the interaction of C<substr> and threads.
1522 Check that upgrading and assigning scalars works.
1528 Check that Unicode in the lexer works.
1534 Check that Unicode and C<tie> work.
1538 F<t/comp/final_line_num.t>
1540 See if line numbers are correct at EOF
1544 F<t/comp/form_scope.t>
1546 See if format scoping works
1550 F<t/comp/line_debug.t>
1552 See if C<< @{"_<$file"} >> works
1556 F<t/op/filetest_t.t>
1558 See if -t file test works
1570 Tests malfunctions of utf8 cache
1576 Test unicode \p{} regex constructs
1580 =head2 Testing improvements
1586 It's now possible to override C<PERL5OPT> and friends in F<t/TEST>
1591 =head1 New or Changed Diagnostics
1593 Several new diagnostics, see L<perldiag> for details.
1599 C<Bad plugin affecting keyword '%s'>
1603 C<gmtime(%.0f) too large>
1607 C<Lexing code attempted to stuff non-Latin-1 character into Latin-1 input>
1611 C<Lexing code internal error (%s)>
1615 C<localtime(%.0f) too large>
1619 C<Overloaded dereference did not return a reference>
1623 C<Overloaded qr did not return a REGEXP>
1627 C<Perl_pmflag() is deprecated, and will be removed from the XS API>
1631 New warning category C<illegalproto>
1635 Illegal character in prototype for %s : %s
1636 Prototype after '%c' for %s : %s
1638 have been moved from the C<syntax> top-level warnings category into a new
1639 first-level category, C<illegalproto>. These two warnings are currently the
1640 only ones emitted during parsing of an invalid/illegal prototype, so one
1643 no warnings 'illegalproto';
1645 to suppress only those, but not other syntax-related warnings. Warnings where
1646 prototypes are changed, ignored, or not met are still in the C<prototype>
1647 category as before. (Matt S. Trout)
1651 lvalue attribute ignored after the subroutine has been defined
1653 This new warning is issued when one attempts to mark a subroutine as
1654 lvalue after it has been defined.
1658 warn if C<++> or C<--> are unable to change the value because it's
1659 beyond the limit of representation
1661 This uses a new warnings category: "imprecision".
1665 C<lc>, C<uc>, C<lcfirst>, and C<ucfirst> warn when passed undef.
1669 Show constant in "Useless use of a constant in void context"
1673 Make the new warning report undef constants as undef
1677 Add a new warning, "Prototype after '%s'"
1681 Tweak the "Illegal character in prototype" warning so it's more precise
1682 when reporting illegal characters after _
1686 Correct the unintended interpolation of C<$\> in regex
1690 Make overflow warnings in C<gmtime> and C<localtime> only occur when
1691 warnings are enabled
1695 Improve mro merging error messages.
1697 They are now very similar to those produced by Algorithm::C3.
1701 Amelioration of the error message "Unrecognized character %s in column %d"
1703 Changes the error message to "Unrecognized character %s; marked by E<lt>--
1704 HERE after %sE<lt>-- HERE near column %d". This should make it a little
1705 simpler to spot and correct the suspicious character.
1709 Explicitely point to C<$.> when it causes an uninitialized warning for
1710 ranges in scalar context
1714 C<split> now warns when called in void context
1718 C<printf>-style functions called with too few arguments will now issue the
1719 warning C<"Missing argument in %s"> [perl #71000]
1723 C<panic: sv_chop %s>
1725 This new fatal error occurs when the C routine C<Perl_sv_chop()> was
1726 passed a position that is not within the scalar's string buffer. This
1727 could be caused by buggy XS code, and at this point recovery is not
1732 C<Deep recursion on subroutine "%s">
1734 It is now possible to change the depth threshold for this warning from the
1735 default of 100, by recompiling the F<perl> binary, setting the C
1736 pre-processor macro C<PERL_SUB_DEPTH_WARN> to the desired value.
1740 Perl now properly returns a syntax error instead of segfaulting
1741 if C<each>, C<keys>, or C<values> is used without an argument.
1745 C<tell()> now fails properly if called without an argument and when no
1746 previous file was read.
1748 C<tell()> now returns C<-1>, and sets errno to C<EBADF>, thus restoring
1749 the 5.8.x behaviour.
1753 C<overload> no longer implicitly unsets fallback on repeated 'use
1758 POSIX::strftime() can now handle Unicode characters in the format string.
1762 The Windows select() implementation now supports all empty C<fd_set>s
1767 The "syntax" category was removed from 5 warnings that should only be in
1772 Three fatal C<pack>/C<unpack> error messages have been normalized to
1777 "Unicode character is illegal" has been rephrased to be more accurate
1779 It now reads C<Unicode non-character is illegal in interchange> and the
1780 perldiag documentation has been expanded a bit.
1784 Perl now defaults to issuing a warning if a deprecated language feature
1787 To disable this feature in a given lexical scope, you should use C<no
1788 warnings 'deprecated';> For information about which language features
1789 are deprecated and explanations of various deprecation warnings, please
1794 The following diagnostics have been removed:
1804 C<Can't locate package %s for the parents of %s>
1806 This warning has been removed. In general, it only got produced in
1807 conjunction with other warnings, and removing it allowed an ISA lookup
1808 optimisation to be added.
1812 C<v-string in use/require is non-portable>
1816 =head1 Utility Changes
1824 Now looks in C<include-fixed> too, which is a recent addition to gcc's
1831 No longer incorrectly treats enum values like macros (Daniel Burr).
1833 Now handles C++ style constants (C<//>) properly in enums. (A patch from
1834 Rainer Weikusat was used; Daniel Burr also proposed a similar fix).
1840 C<LVALUE> subroutines now work under the debugger.
1842 The debugger now correctly handles proxy constant subroutines, and
1849 F<perlbug> now uses C<%Module::CoreList::bug_tracker> to print out upstream bug
1852 Where the user names a module that their bug report is about, and we know the
1853 URL for its upstream bug tracker, provide a message to the user explaining
1854 that the core copies the CPAN version directly, and provide the URL for
1855 reporting the bug directly to upstream.
1861 Perl 5.11.0 added a new utility F<perlthanks>, which is a variant of
1862 F<perlbug>, but for sending non-bug-reports to the authors and maintainers
1863 of Perl. Getting nothing but bug reports can become a bit demoralising:
1864 we'll see if this changes things.
1870 No longer reports "Message sent" when it hasn't actually sent the message
1876 Fixed bugs with the match() operator in list context, remove mention of
1881 =head1 Selected Bug Fixes
1887 Ensure that pp_qr returns a new regexp SV each time. Resolves RT #69852.
1889 Instead of returning a(nother) reference to the (pre-compiled) regexp in the
1890 optree, use reg_temp_copy() to create a copy of it, and return a reference to
1891 that. This resolves issues about Regexp::DESTROY not being called in a timely
1892 fashion (the original bug tracked by RT #69852), as well as bugs related to
1893 blessing regexps, and of assigning to regexps, as described in correspondence
1894 added to the ticket.
1896 It transpires that we also need to undo the SvPVX() sharing when ithreads
1897 cloning a Regexp SV, because mother_re is set to NULL, instead of a cloned
1898 copy of the mother_re. This change might fix bugs with regexps and threads in
1899 certain other situations, but as yet neither tests nor bug reports have
1900 indicated any problems, so it might not actually be an edge case that it's
1905 Several compilation errors and segfaults when perl was built with C<-Dmad> were fixed.
1909 Fixes for lexer API changes in 5.11.2 which broke NYTProf's savesrc option.
1913 C<-t> should only return TRUE for file handles connected to a TTY
1915 The Microsoft C version of C<isatty()> returns TRUE for all
1916 character mode devices, including the F</dev/null>-style "nul"
1917 device and printers like "lpt1".
1921 Fixed a regression caused by commit fafafbaf which caused a panic during
1922 parameter passing [perl #70171]
1926 On systems which in-place edits without backup files, -i'*' now works as
1927 the documentation says it does [perl #70802]
1931 Saving and restoring magic flags no longer loses readonly flag.
1935 The malformed syntax C<grep EXPR LIST> (note the missing comma) no longer
1936 causes abrupt and total failure.
1940 Regular expressions compiled with C<qr{}> literals properly set C<$'> when
1945 Using named subroutines with C<sort> should no longer lead to bus errors [perl
1950 Numerous bugfixes catch small issues caused by the recently-added Lexer API.
1954 Smart match against C<@_> sometimes gave false negatives. [perl #71078]
1958 C<$@> may now be assigned a read-only value (without error or busting
1963 C<sort> called recursively from within an active comparison subroutine no
1964 longer causes a bus error if run multiple times. [perl #71076]
1968 Tie::Hash::NamedCapture::* will not abort if passed bad input (RT #71828)
1972 @_ and $_ no longer leak under threads (RT #34342 and #41138, also
1977 C<-I> on shebang line now adds directories in front of @INC
1978 as documented, and as does C<-I> when specified on the command-line.
1982 C<kill> is now fatal when called on non-numeric process identifiers.
1983 Previously, an C<undef> process identifier would be interpreted as a
1984 request to kill process 0, which would terminate the current process
1985 group on POSIX systems. Since process identifiers are always integers,
1986 killing a non-numeric process is now fatal.
1990 5.10.0 inadvertently disabled an optimisation, which caused a measurable
1991 performance drop in list assignment, such as is often used to assign
1992 function parameters from C<@_>. The optimisation has been re-instated, and
1993 the performance regression fixed. (This fix is also present in 5.10.1)
1997 Fixed memory leak on C<while (1) { map 1, 1 }> [RT #53038].
2001 Some potential coredumps in PerlIO fixed [RT #57322,54828].
2005 The debugger now works with lvalue subroutines.
2009 The debugger's C<m> command was broken on modules that defined constants
2014 C<crypt> and string complement could return tainted values for untainted
2015 arguments [RT #59998].
2019 The C<-i>I<.suffix> command-line switch now recreates the file using
2020 restricted permissions, before changing its mode to match the original
2021 file. This eliminates a potential race condition [RT #60904].
2025 On some Unix systems, the value in C<$?> would not have the top bit set
2026 (C<$? & 128>) even if the child core dumped.
2030 Under some circumstances, C<$^R> could incorrectly become undefined
2035 In the XS API, various hash functions, when passed a pre-computed hash where
2036 the key is UTF-8, might result in an incorrect lookup.
2040 XS code including F<XSUB.h> before F<perl.h> gave a compile-time error
2045 C<< $object-E<gt>isa('Foo') >> would report false if the package C<Foo> didn't
2046 exist, even if the object's C<@ISA> contained C<Foo>.
2050 Various bugs in the new-to 5.10.0 mro code, triggered by manipulating
2051 C<@ISA>, have been found and fixed.
2055 Bitwise operations on references could crash the interpreter, e.g.
2056 C<$x=\$y; $x |= "foo"> [RT #54956].
2060 Patterns including alternation might be sensitive to the internal UTF-8
2061 representation, e.g.
2063 my $byte = chr(192);
2064 my $utf8 = chr(192); utf8::upgrade($utf8);
2065 $utf8 =~ /$byte|X}/i; # failed in 5.10.0
2069 Within UTF8-encoded Perl source files (i.e. where C<use utf8> is in
2070 effect), double-quoted literal strings could be corrupted where a C<\xNN>,
2071 C<\0NNN> or C<\N{}> is followed by a literal character with ordinal value
2072 greater than 255 [RT #59908].
2076 C<B::Deparse> failed to correctly deparse various constructs:
2077 C<readpipe STRING> [RT #62428], C<CORE::require(STRING)> [RT #62488],
2078 C<sub foo(_)> [RT #62484].
2082 Using C<setpgrp> with no arguments could corrupt the perl stack.
2086 The block form of C<eval> is now specifically trappable by C<Safe> and
2087 C<ops>. Previously it was erroneously treated like string C<eval>.
2091 In 5.10.0, the two characters C<[~> were sometimes parsed as the smart
2092 match operator (C<~~>) [RT #63854].
2096 In 5.10.0, the C<*> quantifier in patterns was sometimes treated as
2097 C<{0,32767}> [RT #60034, #60464]. For example, this match would fail:
2099 ("ab" x 32768) =~ /^(ab)*$/
2103 C<shmget> was limited to a 32 bit segment size on a 64 bit OS [RT #63924].
2107 Using C<next> or C<last> to exit a C<given> block no longer produces a
2108 spurious warning like the following:
2110 Exiting given via last at foo.pl line 123
2114 On Windows, C<'.\foo'> and C<'..\foo'> were treated differently than
2115 C<'./foo'> and C<'../foo'> by C<do> and C<require> [RT #63492].
2119 Assigning a format to a glob could corrupt the format; e.g.:
2121 *bar=*foo{FORMAT}; # foo format now bad
2125 Attempting to coerce a typeglob to a string or number could cause an
2126 assertion failure. The correct error message is now generated,
2127 C<Can't coerce GLOB to I<$type>>.
2131 Under C<use filetest 'access'>, C<-x> was using the wrong access mode. This
2132 has been fixed [RT #49003].
2136 C<length> on a tied scalar that returned a Unicode value would not be
2137 correct the first time. This has been fixed.
2141 Using an array C<tie> inside in array C<tie> could SEGV. This has been
2146 A race condition inside C<PerlIOStdio_close()> has been identified and
2147 fixed. This used to cause various threading issues, including SEGVs.
2151 In C<unpack>, the use of C<()> groups in scalar context was internally
2152 placing a list on the interpreter's stack, which manifested in various
2153 ways, including SEGVs. This is now fixed [RT #50256].
2157 Magic was called twice in C<substr>, C<\&$x>, C<tie $x, $m> and C<chop>.
2158 These have all been fixed.
2162 A 5.10.0 optimisation to clear the temporary stack within the implicit
2163 loop of C<s///ge> has been reverted, as it turned out to be the cause of
2164 obscure bugs in seemingly unrelated parts of the interpreter [commit
2169 The line numbers for warnings inside C<elsif> are now correct.
2173 The C<..> operator now works correctly with ranges whose ends are at or
2174 close to the values of the smallest and largest integers.
2178 C<binmode STDIN, ':raw'> could lead to segmentation faults on some platforms.
2179 This has been fixed [RT #54828].
2183 An off-by-one error meant that C<index $str, ...> was effectively being
2184 executed as C<index "$str\0", ...>. This has been fixed [RT #53746].
2188 Various leaks associated with named captures in regexes have been fixed
2193 A weak reference to a hash would leak. This was affecting C<DBI>
2198 Using (?|) in a regex could cause a segfault [RT #59734].
2202 Use of a UTF-8 C<tr//> within a closure could cause a segfault [RT #61520].
2206 Calling C<Perl_sv_chop()> or otherwise upgrading an SV could result in an
2207 unaligned 64-bit access on the SPARC architecture [RT #60574].
2211 In the 5.10.0 release, C<inc_version_list> would incorrectly list
2212 C<5.10.*> after C<5.8.*>; this affected the C<@INC> search order
2217 In 5.10.0, C<pack "a*", $tainted_value> returned a non-tainted value
2222 In 5.10.0, C<printf> and C<sprintf> could produce the fatal error
2223 C<panic: utf8_mg_pos_cache_update> when printing UTF-8 strings
2228 In the 5.10.0 release, a dynamically created C<AUTOLOAD> method might be
2229 missed (method cache issue) [RT #60220,60232].
2233 In the 5.10.0 release, a combination of C<use feature> and C<//ee> could
2234 cause a memory leak [RT #63110].
2238 C<-C> on the shebang (C<#!>) line is once more permitted if it is also
2239 specified on the command line. C<-C> on the shebang line used to be a
2240 silent no-op I<if> it was not also on the command line, so perl 5.10.0
2241 disallowed it, which broke some scripts. Now perl checks whether it is
2242 also on the command line and only dies if it is not [RT #67880].
2246 In 5.10.0, certain types of re-entrant regular expression could crash,
2247 or cause the following assertion failure [RT #60508]:
2249 Assertion rx->sublen >= (s - rx->subbeg) + i failed
2253 Previously missing files from Unicode 5.1 Character Database are now included.
2257 C<TMPDIR> is now honored when opening an anonymous temporary file
2261 =head1 Platform Specific Changes
2263 =head2 New Platforms
2269 Patches from the Haiku maintainers have been merged in. Perl should now
2274 Perl should now build on MirOS BSD.
2279 =head2 Discontinued Platforms
2285 Support for Apollo DomainOS was removed in Perl 5.11.0
2289 Support for Tenon Intersystems MachTen Unix layer for MacOS Classic was
2290 removed in Perl 5.11.0
2294 Support for Atari MiNT was removed in Perl 5.11.0.
2298 =head2 Updated Platforms
2302 =item Darwin (Mac OS X)
2308 Skip testing the be_BY.CP1131 locale on Darwin 10 (Mac OS X 10.6),
2309 as it's still buggy.
2313 Correct infelicities in the regexp used to identify buggy locales
2314 on Darwin 8 and 9 (Mac OS X 10.4 and 10.5, respectively).
2324 Fix thread library selection [perl #69686]
2334 Initial support for mingw64 is now available
2338 Various bits of Perl's build infrastructure are no longer converted to
2339 win32 line endings at release time. If this hurts you, please report the
2340 problem with the L<perlbug> program included with perl.
2344 Always add a manifest resource to C<perl.exe> to specify the C<trustInfo>
2345 settings for Windows Vista and later. Without this setting Windows
2346 will treat C<perl.exe> as a legacy application and apply various
2347 heuristics like redirecting access to protected file system areas
2348 (like the "Program Files" folder) to the users "VirtualStore"
2349 instead of generating a proper "permission denied" error.
2351 For VC8 and VC9 this manifest setting is automatically generated by
2352 the compiler/linker (together with the binding information for their
2353 respective runtime libraries); for all other compilers we need to
2354 embed the manifest resource explicitly in the external resource file.
2356 This change also requests the Microsoft Common-Controls version 6.0
2357 (themed controls introduced in Windows XP) via the dependency list
2358 in the assembly manifest. For VC8 and VC9 this is specified using the
2359 C</manifestdependency> linker commandline option instead.
2363 Improved message window handling means that C<alarm> and C<kill> messages
2364 will no longer be dropped under race conditions.
2374 Enable IPv6 support on cygwin 1.7 and newer
2384 Make -UDEBUGGING the default on VMS for 5.12.0.
2386 Like it has been everywhere else for ages and ages. Also make
2387 command-line selection of -UDEBUGGING and -DDEBUGGING work in
2388 configure.com; before the only way to turn it off was by saying
2389 no in answer to the interactive question.
2393 The default pipe buffer size on VMS has been updated to 8192 on 64-bit
2398 Reads from the in-memory temporary files of C<PerlIO::scalar> used to fail
2399 if C<$/> was set to a numeric reference (to indicate record-style reads).
2404 VMS now supports C<getgrgid>.
2408 Many improvements and cleanups have been made to the VMS file name handling
2409 and conversion code.
2413 Enabling the C<PERL_VMS_POSIX_EXIT> logical name now encodes a POSIX exit
2414 status in a VMS condition value for better interaction with GNV's bash
2415 shell and other utilities that depend on POSIX exit values. See
2416 L<perlvms/"$?"> for details.
2420 C<File::Copy> now detects Unix compatibility mode on VMS.
2426 Removed F<libbsd> for AIX 5L and 6.1. Only C<flock()> was used from F<libbsd>.
2428 Removed F<libgdbm> for AIX 5L and 6.1. The F<libgdbm> is delivered as an
2429 optional package with the AIX Toolbox. Unfortunately the 64 bit version
2432 Hints changes mean that AIX 4.2 should work again.
2436 On Cygwin we now strip the last number from the DLL. This has been the
2437 behaviour in the cygwin.com build for years. The hints files have been
2443 The hints files now identify the correct threading libraries on FreeBSD 7
2448 We now work around a bizarre preprocessor bug in the Irix 6.5 compiler:
2449 C<cc -E -> unfortunately goes into K&R mode, but C<cc -E file.c> doesn't.
2453 Hints now supports versions 5.*.
2457 Various changes from Stratus have been merged in.
2461 There is now support for Symbian S60 3.2 SDK and S60 5.0 SDK.
2465 =head1 Known Problems
2467 This is a list of some significant unfixed bugs, which are regressions
2468 from either 5.10.0 or 5.8.x.
2474 C<List::Util::first> misbehaves in the presence of a lexical C<$_>
2475 (typically introduced by C<my $_> or implicitly by C<given>). The variable
2476 which gets set for each iteration is the package variable C<$_>, not the
2477 lexical C<$_> [RT #67694].
2479 A similar issue may occur in other modules that provide functions which
2480 take a block as their first argument, like
2482 foo { ... $_ ...} list
2486 Some regexes may run much more slowly when run in a child thread compared
2487 with the thread the pattern was compiled into [RT #55600].
2491 Untriaged test crashes on Windows 2000
2493 Several porters have reported mysterious crashes when Perl's entire test suite is run after a build on certain Windows 2000 systems. When run by hand, the individual tests reportedly work fine.
2497 Known test failures on VMS
2499 Perl 5.11.1 fails a small set of core and CPAN tests as of this release.
2500 With luck, that'll be sorted out for 5.11.2
2504 Known test failures on VMS
2506 Perl 5.11.2 fails a small set of core and CPAN tests as of this
2507 release. With luck, that'll be sorted out for 5.11.3.
2511 =head1 Acknowledgements
2513 Perl 5.12.0 represents approximately two years of development since
2514 Perl 5.10.0 and contains __ lines of changes across ___ files
2515 from __ authors and committers:
2519 Many of the changes included in this version originated in the CPAN
2520 modules included in Perl's core. We're grateful to the entire CPAN
2521 community for helping Perl to flourish.
2523 =head1 Reporting Bugs
2525 If you find what you think is a bug, you might check the articles
2526 recently posted to the comp.lang.perl.misc newsgroup and the perl
2527 bug database at L<http://rt.perl.org/perlbug/>. There may also be
2528 information at L<http://www.perl.org/>, the Perl Home Page.
2530 If you believe you have an unreported bug, please run the B<perlbug>
2531 program included with your release. Be sure to trim your bug down
2532 to a tiny but sufficient test case. Your bug report, along with the
2533 output of C<perl -V>, will be sent off to perlbug@perl.org to be
2534 analyzed by the Perl porting team.
2536 If the bug you are reporting has security implications, which make it
2537 inappropriate to send to a publicly archived mailing list, then please send
2538 it to perl5-security-report@perl.org. This points to a closed subscription
2539 unarchived mailing list, which includes all the core committers, who be able
2540 to help assess the impact of issues, figure out a resolution, and help
2541 co-ordinate the release of patches to mitigate or fix the problem across all
2542 platforms on which Perl is supported. Please only use this address for
2543 security issues in the Perl core, not for modules independently
2544 distributed on CPAN.
2548 The F<Changes> file for an explanation of how to view exhaustive details
2551 The F<INSTALL> file for how to build Perl.
2553 The F<README> file for general stuff.
2555 The F<Artistic> and F<Copying> files for copyright information.