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 Perl can now handle every Unicode character property. A new pod,
84 L<perluniprops>, lists all available non-Unihan character properties. By
85 default the Unihan properties and certain others (deprecated and Unicode
86 internal-only ones) are not exposed. See below for more details on
87 these; there is also a section in the pod listing them, and explaining
88 why they are not exposed.
90 Perl now fully supports the Unicode compound-style of using C<=> and C<:>
91 in writing regular expressions: C<\p{property=value}> and
92 C<\p{property:value}> (both of which mean the same thing).
94 Perl now fully supports the Unicode loose matching rules for text
95 between the braces in C<\p{...}> constructs. In addition, Perl allows
96 underscores between digits of numbers.
98 All the Unicode-defined synonyms for properties and property values are
101 C<qr/\X/>, which matches a Unicode logical character, has been expanded to work
102 better with various Asian languages. It now is defined as an C<extended
103 grapheme cluster>. (See L<http://www.unicode.org/reports/tr29/>).
104 Anything matched previously and that made sense will continue to be
105 matched, but in addition:
111 C<\X> will now not break apart a C<S<CR LF>> sequence.
115 C<\X> will now match a sequence including the C<ZWJ> and C<ZWNJ> characters.
119 C<\X> will now always match at least one character, including an initial mark.
120 Marks generally come after a base character, but it is possible in Unicode to
121 have them in isolation, and C<\X> will now handle that case, for example at the
122 beginning of a line or after a C<ZWSP>. And this is the part where C<\X>
123 doesn't match the things that it used to that don't make sense. Formerly, for
124 example, you could have the nonsensical case of an accented LF.
128 C<\X> will now match a (Korean) Hangul syllable sequence, and the Thai and Lao
133 Otherwise, this change should be transparent for the non-affected languages.
135 C<\p{...}> matches using the Canonical_Combining_Class property were
136 completely broken in previous Perls. This is now fixed.
138 In previous Perls, the Unicode C<Decomposition_Type=Compat> property and a
139 Perl extension had the same name, which led to neither matching all the
140 correct values (with more than 100 mistakes in one, and several thousand
141 in the other). The Perl extension has now been renamed to be
142 C<Decomposition_Type=Noncanonical> (short: C<dt=noncanon>). It has the same
143 meaning as was previously intended, namely the union of all the
144 non-canonical Decomposition types, with Unicode C<Compat> being just one of
147 C<\p{Uppercase}> and C<\p{Lowercase}> have been brought into line with the
148 Unicode definitions. This means they each match a few more characters
151 C<\p{Cntrl}> now matches the same characters as C<\p{Control}>. This means it
152 no longer will match Private Use (gc=co), Surrogates (gc=cs), nor Format
153 (gc=cf) code points. The Format code points represent the biggest
154 possible problem. All but 36 of them are either officially deprecated
155 or strongly discouraged from being used. Of those 36, likely the most
156 widely used are the soft hyphen (U+00AD), and BOM, ZWSP, ZWNJ, WJ, and
157 similar, plus bidirectional controls.
159 C<\p{Alpha}> now matches the same characters as C<\p{Alphabetic}>. The Perl
160 definition included a number of things that aren't really alpha (all
161 marks), while omitting many that were. As a direct consequence, the
162 definitions of C<\p{Alnum}> and C<\p{Word}> which depend on Alpha also change.
164 C<\p{Word}> also now doesn't match certain characters it wasn't supposed
165 to, such as fractions.
167 C<\p{Print}> no longer matches the line control characters: Tab, LF, CR,
168 FF, VT, and NEL. This brings it in line with the documentation.
170 C<\p{Decomposition_Type=Canonical}> now includes the Hangul syllables.
172 The Numeric type property has been extended to include the Unihan
175 There is a new Perl extension, the 'Present_In', or simply 'In',
176 property. This is an extension of the Unicode Age property, but
177 C<\p{In=5.0}> matches any code point whose usage has been determined
178 I<as of> Unicode version 5.0. The C<\p{Age=5.0}> only matches code points
179 added in I<precisely> version 5.0.
181 A number of properties did not have the correct values for unassigned
182 code points. This is now fixed. The affected properties are
183 Bidi_Class, East_Asian_Width, Joining_Type, Decomposition_Type,
184 Hangul_Syllable_Type, Numeric_Type, and Line_Break.
186 The Default_Ignorable_Code_Point, ID_Continue, and ID_Start properties
187 have been updated to their current Unicode definitions.
189 Certain properties that are supposed to be Unicode internal-only were
190 erroneously exposed by previous Perls. Use of these in regular
191 expressions will now generate, if enabled, a deprecated warning message.
192 The properties are: Other_Alphabetic, Other_Default_Ignorable_Code_Point,
193 Other_Grapheme_Extend, Other_ID_Continue, Other_ID_Start, Other_Lowercase,
194 Other_Math, and Other_Uppercase.
196 An installation can now fairly easily change which Unicode properties
197 Perl understands. As mentioned above, certain properties are by default
198 turned off. These include all the Unihan properties (which should be
199 accessible via the CPAN module Unicode::Unihan) and any deprecated or
200 Unicode internal-only property that Perl has never exposed.
202 The generated files in the C<lib/unicore/To> directory are now more
203 clearly marked as being stable, directly usable by applications.
204 New hash entries in them give the format of the normal entries,
205 which allows for easier machine parsing. Perl can generate files
206 in this directory for any property, though most are suppressed. An
207 installation can choose to change which get written. Instructions
208 are in L<perluniprops>.
210 =head2 Regular Expressions
212 U+0FFFF is now a legal character in regular expressions.
214 =head2 Unicode properties
216 C<\p{XDigit}> now matches the same characters as C<\p{Hex_Digit}>. This
217 means that in addition to the characters it currently matches,
218 C<[A-Fa-f0-9]>, it will also match their fullwidth equivalent forms, for
219 example U+FF10: FULLWIDTH DIGIT ZERO.
221 =head2 Unicode Character Database 5.1.0
223 The copy of the Unicode Character Database included in Perl 5.11.0 has
224 been updated to 5.1.0 from 5.0.0. See
225 L<http://www.unicode.org/versions/Unicode5.1.0/#Notable_Changes> for the
228 =head2 A proper interface for pluggable Method Resolution Orders
230 As of Perl 5.11.0 there is a new interface for plugging and using method
231 resolution orders other than the default (linear depth first search).
232 The C3 method resolution order added in 5.10.0 has been re-implemented as
233 a plugin, without changing its Perl-space interface. See L<perlmroapi> for
236 =head2 The C<overloading> pragma
238 This pragma allows you to lexically disable or enable overloading
239 for some or all operations. (Yuval Kogman)
241 =head2 C<\N> regex escape
243 A new regex escape has been added, C<\N>. It will match any character that
244 is not a newline, independently from the presence or absence of the single
245 line match modifier C</s>. (If C<\N> is followed by an opening brace and
246 by a letter, perl will still assume that a Unicode character name is
247 coming, so compatibility is preserved.) (Rafael Garcia-Suarez)
249 =head2 Implicit strictures
251 Using the C<use VERSION> syntax with a version number greater or equal
252 to 5.11.0 will also lexically enable strictures just like C<use strict>
253 would do (in addition to enabling features.) So, the following:
262 =head2 Parallel tests
264 The core distribution can now run its regression tests in parallel on
265 Unix-like platforms. Instead of running C<make test>, set C<TEST_JOBS> in
266 your environment to the number of tests to run in parallel, and run
267 C<make test_harness>. On a Bourne-like shell, this can be done as
269 TEST_JOBS=3 make test_harness # Run 3 tests in parallel
271 An environment variable is used, rather than parallel make itself, because
272 L<TAP::Harness> needs to be able to schedule individual non-conflicting test
273 scripts itself, and there is no standard interface to C<make> utilities to
274 interact with their job schedulers.
276 Note that currently some test scripts may fail when run in parallel (most
277 notably C<ext/IO/t/io_dir.t>). If necessary run just the failing scripts
278 again sequentially and see if the failures go away.
280 =head2 The C<...> operator
282 A new operator, C<...>, nicknamed the Yada Yada operator, has been added.
283 It is intended to mark placeholder code that is not yet implemented.
284 See L<perlop/"Yada Yada Operator">. (chromatic)
286 =head2 DTrace support
288 Some support for DTrace has been added. See "DTrace support" in F<INSTALL>.
290 =head2 Support for C<configure_requires> in CPAN module metadata
292 Both C<CPAN> and C<CPANPLUS> now support the C<configure_requires> keyword
293 in the F<META.yml> metadata file included in most recent CPAN distributions.
294 This allows distribution authors to specify configuration prerequisites that
295 must be installed before running F<Makefile.PL> or F<Build.PL>.
297 See the documentation for C<ExtUtils::MakeMaker> or C<Module::Build> for more
298 on how to specify C<configure_requires> when creating a distribution for CPAN.
300 =head2 C<each> is now more flexible
302 The C<each> function can now operate on arrays.
304 =head2 Y2038 compliance
306 Perl's core time-related functions are now Y2038 compliant. (With 29
309 =head2 C<$,> flexibility
311 The variable C<$,> may now be tied.
313 =head2 // in where clauses
315 // now behaves like || in when clauses
317 =head2 Enabling warnings from your shell environment
319 You can now set C<-W> from the C<PERL5OPT> environment variable
321 =head2 C<delete local>
323 C<delete local> now allows you to locally delete a hash entry.
325 =head2 New support for Abstract namespace sockets
327 Abstract namespace sockets are Linux-specific socket type that live in
328 AF_UNIX family, slightly abusing it to be able to use arbitrary
329 character arrays as addresses: They start with nul byte and are not
330 terminated by nul byte, but with the length passed to the socket()
333 =head2 Add C<package NAME VERSION> syntax
335 This new syntax allows a module author to set the $VERSION of a namespace
336 when the namespace is declared with 'package'. It eliminates the need
337 for C<our $VERSION = ...> and similar constructs. E.g.
339 package Foo::Bar 1.23;
340 # $Foo::Bar::VERSION == 1.23
342 There are several advantages to this:
348 C<$VERSION> is parsed in I<exactly> the same way as C<use NAME VERSION>
352 C<$VERSION> is set at compile time
356 Eliminates C<$VERSION = ...> and C<eval $VERSION> clutter
360 As it requires VERSION to be a numeric literal or v-string
361 literal, it can be statically parsed by toolchain modules
362 without C<eval> the way MM-E<gt>parse_version does for C<$VERSION = ...>
366 Alpha versions with underscores do not need to be quoted; static
367 parsing will preserve the underscore, but during compilation, Perl
368 will remove underscores as it does for all numeric literals
370 It does not break old code with only C<package NAME>, but code that uses
371 C<package NAME VERSION> will need to be restricted to perl 5.11.X or newer
372 This is analogous to the change to C<open> from two-args to three-args.
373 Users requiring the latest Perl will benefit, and perhaps N years from
374 now it will become standard practice when Perl 5.12 is targeted the way
379 =head1 Incompatible Changes
381 =head2 Version number formats
383 Acceptable version number formats have been formalized into "strict" and
384 "lax" rules. C<package NAME VERSION> takes a strict version number. C<use
385 NAME VERSION> takes a lax version number. C<UNIVERSAL::VERSION> and the
386 L<version> object constructors take lax version numbers. Providing an
387 invalid version will result in a fatal error.
389 These formats will be documented fully in the L<version> module in a
390 subsequent release of Perl 5.11. To a first approximation, a "strict"
391 version number is a positive decimal number (integer or decimal-fraction)
392 without exponentiation or else a dotted-decimal v-string with a leading 'v'
393 character and at least three components. A "lax" version number allows
394 v-strings with fewer than three components or without a leading 'v'. Under
395 "lax" rules, both decimal and dotted-decimal versions may have a trailing
396 "alpha" component separated by an underscore character after a fractional
397 or dotted-decimal component.
399 The L<version> module adds C<version::is_strict> and C<version::is_lax>
400 functions to check a scalar against these rules.
402 =head2 Unicode interpretation of \w, \d, \s, and the POSIX character classes redefined.
404 Previous versions of Perl tried to map POSIX style character class
405 definitions onto Unicode property names so that patterns would "do what
406 you meant" when matches were made against latin-1 or unicode strings.
407 This proved to be a mistake, breaking character class negation, causing
408 forward compatibility problems (as Unicode keeps updating their property
409 definitions and adding new characters), and other problems.
411 Therefore we have now defined a new set of artificial "unicode" property
412 names which will be used to do unicode matching of patterns using POSIX
413 style character classes and perl short-form escape character classes
416 The key change here is that \d will no longer match every digit in the
417 unicode standard (there are thousands) nor will \w match every word
418 character in the standard, instead they will match precisely their POSIX
421 Those needing to match based on Unicode properties can continue to do so
422 by using the \p{} syntax to match whichever property they like,
423 including the new artificial definitions.
425 B<NOTE:> This is a backwards incompatible no-warning change in
426 behaviour. If you are upgrading and you process large volumes of text
427 look for POSIX and Perl style character classes and change them to the
428 relevent property name (by removing the word 'Posix' from the current
431 The following table maps the POSIX character class names, the escapes
432 and the old and new Unicode property mappings:
434 POSIX Esc Class New-Property ! Old-Property
435 ----------------------------------------------+-------------
436 alnum [0-9A-Za-z] IsPosixAlnum ! IsAlnum
437 alpha [A-Za-z] IsPosixAlpha ! IsAlpha
438 ascii [\000-\177] IsASCII = IsASCII
439 blank [\011 ] IsPosixBlank !
440 cntrl [\0-\37\177] IsPosixCntrl ! IsCntrl
441 digit \d [0-9] IsPosixDigit ! IsDigit
442 graph [!-~] IsPosixGraph ! IsGraph
443 lower [a-z] IsPosixLower ! IsLower
444 print [ -~] IsPosixPrint ! IsPrint
445 punct [!-/:-@[-`{-~] IsPosixPunct ! IsPunct
446 space [\11-\15 ] IsPosixSpace ! IsSpace
447 \s [\11\12\14\15 ] IsPerlSpace ! IsSpacePerl
448 upper [A-Z] IsPosixUpper ! IsUpper
449 word \w [0-9A-Z_a-z] IsPerlWord ! IsWord
450 xdigit [0-9A-Fa-f] IsXDigit = IsXDigit
452 If you wish to build perl with the old mapping you may do so by setting
454 #define PERL_LEGACY_UNICODE_CHARCLASS_MAPPINGS 1
456 in regcomp.h, and then setting
458 PERL_TEST_LEGACY_POSIX_CC
460 to true your enviornment when testing.
462 =head2 @INC reorganization
464 In @INC, ARCHLIB and PRIVLIB now occur after after the current version's
465 site_perl and vendor_perl.
467 =head2 Switch statement changes
469 The handling of complex expressions by the C<given>/C<when> switch
470 statement has been enhanced. These enhancements are also available in
471 5.10.1 and subsequent 5.10 releases. There are two new cases where
472 C<when> now interprets its argument as a boolean, instead of an
473 expression to be used in a smart match:
475 =head2 flip-flop operators
477 The C<..> and C<...> flip-flop operators are now evaluated in boolean
478 context, following their usual semantics; see L<perlop/"Range Operators">.
480 Note that, as in perl 5.10.0, C<when (1..10)> will not work to test
481 whether a given value is an integer between 1 and 10; you should use
482 C<when ([1..10])> instead (note the array reference).
484 However, contrary to 5.10.0, evaluating the flip-flop operators in boolean
485 context ensures it can now be useful in a C<when()>, notably for
486 implementing bistable conditions, like in:
488 when (/^=begin/ .. /^=end/) {
492 =head2 defined-or operator
494 A compound expression involving the defined-or operator, as in
495 C<when (expr1 // expr2)>, will be treated as boolean if the first
496 expression is boolean. (This just extends the existing rule that applies
497 to the regular or operator, as in C<when (expr1 || expr2)>.)
499 =head2 Smart match changes
501 This section details more changes brought to the semantics to
502 the smart match operator, that naturally also modify the behaviour
503 of the switch statements where smart matching is implicitly used.
504 These changes were also made for the 5.10.1 release, and will remain in
505 subsequent 5.10 releases.
507 =head3 Changes to type-based dispatch
509 The smart match operator C<~~> is no longer commutative. The behaviour of
510 a smart match now depends primarily on the type of its right hand
511 argument. Moreover, its semantics have been adjusted for greater
512 consistency or usefulness in several cases. While the general backwards
513 compatibility is maintained, several changes must be noted:
519 Code references with an empty prototype are no longer treated specially.
520 They are passed an argument like the other code references (even if they
521 choose to ignore it).
525 C<%hash ~~ sub {}> and C<@array ~~ sub {}> now test that the subroutine
526 returns a true value for each key of the hash (or element of the
527 array), instead of passing the whole hash or array as a reference to
532 Due to the commutativity breakage, code references are no longer
533 treated specially when appearing on the left of the C<~~> operator,
534 but like any vulgar scalar.
538 C<undef ~~ %hash> is always false (since C<undef> can't be a key in a
539 hash). No implicit conversion to C<""> is done (as was the case in perl
544 C<$scalar ~~ @array> now always distributes the smart match across the
545 elements of the array. It's true if one element in @array verifies
546 C<$scalar ~~ $element>. This is a generalization of the old behaviour
547 that tested whether the array contained the scalar.
551 The full dispatch table for the smart match operator is given in
552 L<perlsyn/"Smart matching in detail">.
554 =head3 Smart match and overloading
556 According to the rule of dispatch based on the rightmost argument type,
557 when an object overloading C<~~> appears on the right side of the
558 operator, the overload routine will always be called (with a 3rd argument
559 set to a true value, see L<overload>.) However, when the object will
560 appear on the left, the overload routine will be called only when the
561 rightmost argument is a simple scalar. This way, distributivity of smart
562 match across arrays is not broken, as well as the other behaviours with
563 complex types (coderefs, hashes, regexes). Thus, writers of overloading
564 routines for smart match mostly need to worry only with comparing
565 against a scalar, and possibly with stringification overloading; the
566 other common cases will be automatically handled consistently.
568 C<~~> will now refuse to work on objects that do not overload it (in order
569 to avoid relying on the object's underlying structure). (However, if the
570 object overloads the stringification or the numification operators, and
571 if overload fallback is active, it will be used instead, as usual.)
573 =head2 Labels can't be keywords
575 Labels used as targets for the C<goto>, C<last>, C<next> or C<redo>
576 statements cannot be keywords anymore. This restriction will prevent
577 potential confusion between the C<goto LABEL> and C<goto EXPR> syntaxes:
578 for example, a statement like C<goto print> would jump to a label whose
579 name would be the return value of C<print()>, (usually 1), instead of a
580 label named C<print>. Moreover, the other control flow statements
581 would just ignore any keyword passed to them as a label name. Since
582 such labels cannot be defined anymore, this kind of error will be
585 =head2 Other incompatible changes
591 The boolkeys op moved to the group of hash ops. This breaks binary
596 C<\s> C<\w> and C<\d> once again have the semantics they had in Perl 5.8.x.
600 Filehandles are blessed directly into C<IO::Handle>, as C<FileHandle> is
601 merely a wrapper around C<IO::Handle>.
603 The previous behaviour was to bless Filehandles into L<FileHandle>
604 (an empty proxy class) if it was loaded into memory and otherwise
605 to bless them into C<IO::Handle>.
609 The semantics of C<use feature :5.10*> have changed slightly.
610 See L<"Modules and Pragmata"> for more information.
614 The version control system used for the development of the perl
615 interpreter has been switched from Perforce to git. This is mainly an
616 internal issue that only affects people actively working on the perl core;
617 but it may have minor external visibility, for example in some of details
618 of the output of C<perl -V>. See L<perlrepository> for more information.
622 The internal structure of the C<ext/> directory in the perl source has
623 been reorganised. In general, a module C<Foo::Bar> whose source was
624 stored under F<ext/Foo/Bar/> is now located under F<ext/Foo-Bar/>. Also,
625 nearly all dual-life modules have been moved from F<lib/> to F<ext/>. This
626 is purely a source tarball change, and should make no difference to the
627 compilation or installation of perl, unless you have a very customised build
628 process that explicitly relies on this structure, or which hard-codes the
629 C<nonxs_ext> F<Configure> parameter. Specifically, this change does not by
630 default alter the location of any files in the final installation.
634 As part of the C<Test::Harness> 2.x to 3.x upgrade, the experimental
635 C<Test::Harness::Straps> module has been removed.
636 See L</"Updated Modules"> for more details.
640 As part of the C<ExtUtils::MakeMaker> upgrade, the
641 C<ExtUtils::MakeMaker::bytes> and C<ExtUtils::MakeMaker::vmsish> modules
642 have been removed from this distribution.
646 C<Module::CoreList> no longer contains the C<%:patchlevel> hash.
650 This one is actually a change introduced in 5.10.0, but it was missed
651 from that release's perldelta, so it is mentioned here instead.
653 A bugfix related to the handling of the C</m> modifier and C<qr> resulted
654 in a change of behaviour between 5.8.x and 5.10.0:
656 # matches in 5.8.x, doesn't match in 5.10.0
657 $re = qr/^bar/; "foo\nbar" =~ /$re/m;
661 C<length undef> now returns undef.
665 Unsupported private C API functions are now declared "static" to prevent
666 leakage to Perl's public API.
670 To support the bootstrapping process, F<miniperl> no longer builds with
671 UTF-8 support in the regexp engine.
673 This allows a build to complete with PERL_UNICODE set and a UTF-8 locale.
674 Without this there's a bootstrapping problem, as miniperl can't load the UTF-8
675 components of the regexp engine, because they're not yet built.
679 F<miniperl>'s @INC is now restricted to just C<-I...>, the split of
680 C<$ENV{PERL5LIB}>, and "C<.>"
684 A space or a newline is now required after a C<"#line XXX"> directive.
688 Tied filehandles now have an additional method EOF which provides the EOF type
692 To better match all other flow control statements, C<foreach> may no
693 longer be used as an attribute.
699 From time to time, Perl's developers find it necessary to deprecate
700 features or modules we've previously shipped as part of the core
701 distribution. We are well aware of the pain and frustration that a
702 backwards-incompatible change to Perl can cause for developers building
703 or maintaining software in Perl. You can be sure that when we deprecate
704 a functionality or syntax, it isn't a choice we make lightly. Sometimes,
705 we choose to deprecate functionality or syntax because it was found to
706 be poorly designed or implemented. Sometimes, this is because they're
707 holding back other features or causing performance problems. Sometimes,
708 the reasons are more complex. Wherever possible, we try to keep deprecated
709 functionality available to developers in its previous form for at least
710 one major release. So long as a deprecated feature isn't actively
711 disrupting our ability to maintain and extend Perl, we'll try to leave
712 it in place as long as possible.
714 The following items are now deprecated.
718 =item Use of C<:=> to mean an empty attribute list is now deprecated.
720 An accident of Perl's parser meant that these constructions were all
727 with the C<:> being treated as the start of an attribute list, which
728 ends before the C<=>. As whitespace is not significant here, all are
729 parsed as an empty attribute list, hence all the above are equivalent
730 to, and better written as
734 because no attribute processing is done for an empty list.
736 As is, this meant that C<:=> cannot be used as a new token, without
737 silently changing the meaning of existing code. Hence that particular
738 form is now deprecated, and will become a syntax error. If it is
739 absolutely necessary to have empty attribute lists (for example,
740 because of a code generator) then avoid the warning by adding a space
743 =item C<< UNIVERSAL->import() >>
745 The method C<< UNIVERSAL->import() >> is now deprecated. Attempting to
746 pass import arguments to a C<use UNIVERSAL> statement will result in a
749 =item Use of "goto" to jump into a construct is deprecated
751 Using C<goto> to jump from an outer scope into an inner scope is now
752 deprecated. This rare use case was causing problems in the
753 implementation of scopes.
755 =item Deprecated Modules
757 The following modules will be removed from the core distribution in a future
758 release, and should be installed from CPAN instead. Distributions on CPAN
759 which require these should add them to their prerequisites. The core versions
760 of these modules warnings will issue a deprecation warning.
766 =item L<Pod::Plainer>
772 Switch is buggy and should be avoided. See L<perlsyn/"Switch
773 statements"> for its replacement.
779 C<suidperl> has been removed. It used to provide a mechanism to
780 emulate setuid permission bits on systems that don't support it properly.
782 =item Assignment to $[
786 Remove attrs, which has been deprecated since 1999-10-02.
788 =item Use of the attribute :locked on subroutines.
790 =item Use of "locked" with the attributes pragma.
792 =item Use of "unique" with the attributes pragma.
794 =item Numerous Perl 4-era libraries:
796 F<termcap.pl>, F<tainted.pl>, F<stat.pl>, F<shellwords.pl>, F<pwd.pl>,
797 F<open3.pl>, F<open2.pl>, F<newgetopt.pl>, F<look.pl>, F<find.pl>,
798 F<finddepth.pl>, F<importenv.pl>, F<hostname.pl>, F<getopts.pl>,
799 F<getopt.pl>, F<getcwd.pl>, F<flush.pl>, F<fastcwd.pl>, F<exceptions.pl>,
800 F<ctime.pl>, F<complete.pl>, F<cacheout.pl>, F<bigrat.pl>, F<bigint.pl>,
801 F<bigfloat.pl>, F<assert.pl>, F<abbrev.pl>, F<dotsh.pl>, and
802 F<timelocal.pl> are all now deprecated. Using them will incur a warning.
806 =head1 Modules and Pragmata
808 =head2 Dual-lifed modules moved
810 Dual-lifed modules maintained primarily in the Perl core now live in dist/.
811 Dual-lifed modules maintained primarily on CPAN now live in cpan/
813 In previous releases of Perl, it was customary to enumerate all module
814 changes in this section of the C<perldelta> file. From 5.11.0 forward
815 only notable updates (such as new or deprecated modules ) will be listed
816 in this section. For a complete reference to the versions of modules
817 shipped in a given release of perl, please see L<Module::CoreList>.
819 =head2 New Modules and Pragmata
827 This is a new lexically-scoped alternative for the C<Fatal> module.
828 The bundled version is 2.06_01. Note that in this release, using a string
829 eval when C<autodie> is in effect can cause the autodie behaviour to leak
830 into the surrounding scope. See L<autodie/"BUGS"> for more details.
834 C<Compress::Raw::Bzip2>
836 This has been added to the core (version 2.020).
842 This pragma establishes an ISA relationship with base classes at compile
843 time. It provides the key feature of C<base> without further unwanted
850 This has been added to the core (version 1.39).
854 =head2 Pragmata Changes
862 See L</"The C<overloading> pragma"> above.
868 The C<attrs> pragma has been removed. It had been marked as deprecated since
875 The Unicode F<NameAliases.txt> database file has been added. This has the
876 effect of adding some extra C<\N> character names that formerly wouldn't
877 have been recognised; for example, C<"\N{LATIN CAPITAL LETTER GHA}">.
883 The meaning of the C<:5.10> and C<:5.10.X> feature bundles has
884 changed slightly. The last component, if any (i.e. C<X>) is simply ignored.
885 This is predicated on the assumption that new features will not, in
886 general, be added to maintenance releases. So C<:5.10> and C<:5.10.X>
887 have identical effect. This is a change to the behaviour documented for
894 Upgraded from version 1.00 to 1.01. Performance for single inheritance is 40%
895 faster - see L</"Performance Enhancements"> below.
897 C<mro> is now implemented as an XS extension. The documented interface has not
898 changed. Code relying on the implementation detail that some C<mro::>
899 methods happened to be available at all times gets to "keep both pieces".
905 Supports %.0f formatting internally.
911 Allow overloading of 'qr'.
917 Upgraded from version 1.19 to 1.20.
923 This pragma no longer suppresses C<Use of uninitialized value in range
924 (or flip)> warnings. [perl #71204]
930 Upgraded from 1.13 to 1.14. Added the C<unicode_strings> feature:
932 use feature "unicode_strings";
934 This pragma turns on Unicode semantics for the case-changing operations
935 (C<uc>, C<lc>, C<ucfirst>, C<lcfirst>) on strings that don't have the
936 internal UTF-8 flag set, but that contain single-byte characters between
943 Upgraded from version 1.74 to 1.75.
949 Upgraded from version 0.02 to 0.03.
951 This version introduces the C<stash_name> method to allow subclasses of
952 C<less> to pick where in %^H to store their stash.
958 Upgraded from version 0.77 to 0.81.
960 This version adds support for L</Version number formats> as described earlier
961 in this document and in its own documentation.
967 Upgraded from 1.07 to 1.09.
969 Added new C<warnings::fatal_enabled()> function.
970 This version adds the C<illegalproto> warning category. See also L</New or
971 Changed Diagnostics> for this change.
976 =head2 Updated Modules
980 =item XXX TODO RECALCULATE THIS VS 5.10.0
984 =head2 Removed Modules and Pragmata
992 Removed from the Perl core. Prior version was 'undef'.
998 =head2 New Documentation
1006 This contains instructions on how to build perl for the Haiku platform.
1012 This describes the new interface for pluggable Method Resolution Orders.
1018 This document, by Richard Foley, provides an introduction to the use of
1019 performance and optimization techniques which can be used with particular
1020 reference to perl programs.
1026 This describes how to access the perl source using the I<git> version
1031 L<perlpolicy> extends the "Social contract about contributed modules" into
1032 the beginnings of a document on Perl porting policies.
1036 =head2 Changes to Existing Documentation
1038 The various large F<Changes*> files (which listed every change made to perl
1039 over the last 18 years) have been removed, and replaced by a small file,
1040 also called F<Changes>, which just explains how that same information may
1041 be extracted from the git version control system.
1043 The file F<Porting/patching.pod> has been deleted, as it mainly described
1044 interacting with the old Perforce-based repository, which is now obsolete.
1045 Information still relevant has been moved to L<perlrepository>.
1047 L<perlapi>, L<perlintern>, L<perlmodlib> and L<perltoc> are now all
1048 generated at build time, rather than being shipped as part of the release.
1054 Documented -X overloading.
1058 Documented that C<when()> treats specially most of the filetest operators
1062 Documented C<when> as a syntax modifier
1066 Eliminated "Old Perl threads tutorial", which described 5005 threads.
1068 F<pod/perlthrtut.pod> is the same material reworked for ithreads.
1072 Correct previous documentation: v-strings are not deprecated
1074 With version objects, we need them to use MODULE VERSION syntax. This
1075 patch removes the deprecation notice.
1079 Added security contact information to L<perlsec>
1081 A significant fraction of the core documentation has been updated to clarify
1082 the behavior of Perl's Unicode handling.
1084 Much of the remaining core documentation has been reviewed and edited
1085 for clarity, consistent use of language, and to fix the spelling of Tom
1086 Christiansen's name.
1088 The Pod specification (L<perlpodspec>) has been updated to bring the
1089 specification in line with modern usage already supported by most Pod
1090 systems. A parameter string may now follow the format name in a
1091 "begin/end" region. Links to URIs with a text description are now
1092 allowed. The usage of C<LE<lt>"section"E<gt>> has been marked as
1095 L<if.pm|if> has been documented in L<perlfunc/use> as a means to get
1096 conditional loading of modules despite the implicit BEGIN block around
1101 The documentation for C<$1> in perlvar.pod has been clarified.
1105 =head1 Performance Enhancements
1111 A new internal cache means that C<isa()> will often be faster.
1115 The implementation of C<C3> Method Resolution Order has been optimised -
1116 linearisation for classes with single inheritance is 40% faster. Performance
1117 for multiple inheritance is unchanged.
1121 Under C<use locale>, the locale-relevant information is now cached on
1122 read-only values, such as the list returned by C<keys %hash>. This makes
1123 operations such as C<sort keys %hash> in the scope of C<use locale> much
1128 Empty C<DESTROY> methods are no longer called.
1132 Faster C<Perl_sv_utf8_upgrade()>
1136 Speed up C<keys> on empty hash
1140 C<if (%foo)> has been optimized to be faster than C<if (keys %foo)>
1144 Reversing an array to itself (as in C<@a = reverse @a>) in void context
1145 now happens in-place and is several orders of magnitude faster than it
1146 used to be. It will also preserve non-existent elements whenever
1147 possible, i.e. for non magical arrays or tied arrays with C<EXISTS> and
1152 =head1 Installation and Configuration Improvements
1154 =head2 F<ext/> reorganisation
1156 The layout of directories in F<ext> has been revised. Specifically, all
1157 extensions are now flat, and at the top level, with C</> in pathnames
1158 replaced by C<->, so that F<ext/Data/Dumper/> is now F<ext/Data-Dumper/>,
1159 etc. The names of the extensions as specified to F<Configure>, and as
1160 reported by C<%Config::Config> under the keys C<dynamic_ext>,
1161 C<known_extensions>, C<nonxs_ext> and C<static_ext> have not changed, and
1162 still use C</>. Hence this change will not have any affect once perl is
1163 installed. C<Safe> has been split out from being part of C<Opcode>, and
1164 C<mro> is now an extension in its own right.
1166 Nearly all dual-life modules have been moved from F<lib> to F<ext>, and will
1167 now appear as known C<nonxs_ext>. This will made no difference to the
1168 structure of an installed perl, nor will the modules installed differ,
1169 unless you run F<Configure> with options to specify an exact list of
1170 extensions to build. In this case, you will rapidly become aware that you
1171 need to add to your list, because various modules needed to complete the
1172 build, such as C<ExtUtils::ParseXS>, have now become extensions, and
1173 without them the build will fail well before it attempts to run the
1176 =head2 Configuration improvements
1178 If C<vendorlib> and C<vendorarch> are the same, then they are only added to
1181 C<$Config{usedevel}> and the C-level C<PERL_USE_DEVEL> are now defined if
1182 perl is built with C<-Dusedevel>.
1184 F<Configure> will enable use of C<-fstack-protector>, to provide protection
1185 against stack-smashing attacks, if the compiler supports it.
1187 F<Configure> will now determine the correct prototypes for re-entrant
1188 functions and for C<gconvert> if you are using a C++ compiler rather
1191 On Unix, if you build from a tree containing a git repository, the
1192 configuration process will note the commit hash you have checked out, for
1193 display in the output of C<perl -v> and C<perl -V>. Unpushed local commits
1194 are automatically added to the list of local patches displayed by
1197 USE_ATTRIBUTES_FOR_PERLIO is now reported in the compile-time options
1198 listed by the C<-V> switch.
1200 =head2 Compilation improvements
1202 As part of the flattening of F<ext>, all extensions on all platforms are
1203 built by F<make_ext.pl>. This replaces the Unix-specific
1204 F<ext/util/make_ext>, VMS-specific F<make_ext.com> and Win32-specific
1205 F<win32/buildext.pl>.
1207 =head1 Changed Internals
1213 C<Perl_pmflag> has been removed from the public API. Calling it now
1214 generates a deprecation warning, and it will be removed in a future
1215 release. Although listed as part of the API, it was never documented,
1216 and only ever used in F<toke.c>, and prior to 5.10, F<regcomp.c>. In
1217 core, it has been replaced by a static function.
1221 Perl_magic_setmglob now knows about globs, fixing RT #71254.
1225 TODO: C<SVt_RV> is gone. RVs are now stored in IVs
1229 TODO: REGEXPs are first class
1233 TODO: OOK is reworked, such that an OOKed scalar is PV not PVIV
1237 The J.R.R. Tolkien quotes at the head of C source file have been checked and
1238 proper citations added, thanks to a patch from Tom Christiansen.
1242 C<Perl_vcroak()> now accepts a null first argument. In addition, a full audit
1243 was made of the "not NULL" compiler annotations, and those for several
1244 other internal functions were corrected.
1248 New macros C<dSAVEDERRNO>, C<dSAVE_ERRNO>, C<SAVE_ERRNO>, C<RESTORE_ERRNO>
1249 have been added to formalise the temporary saving of the C<errno>
1254 The function C<Perl_sv_insert_flags> has been added to augment
1259 The function C<Perl_newSV_type(type)> has been added, equivalent to
1260 C<Perl_newSV()> followed by C<Perl_sv_upgrade(type)>.
1264 The function C<Perl_newSVpvn_flags()> has been added, equivalent to
1265 C<Perl_newSVpvn()> and then performing the action relevant to the flag.
1267 Two flag bits are currently supported.
1275 This will call C<SvUTF8_on()> for you. (Note that this does not convert an
1276 sequence of ISO 8859-1 characters to UTF-8). A wrapper, C<newSVpvn_utf8()>
1277 is available for this.
1283 Call C<Perl_sv_2mortal()> on the new SV.
1287 There is also a wrapper that takes constant strings, C<newSVpvs_flags()>.
1291 The function C<Perl_croak_xs_usage> has been added as a wrapper to
1296 The functions C<PerlIO_find_layer> and C<PerlIO_list_alloc> are now
1301 C<PL_na> has been exterminated from the core code, replaced by local STRLEN
1302 temporaries, or C<*_nolen()> calls. Either approach is faster than C<PL_na>,
1303 which is a pointer deference into the interpreter structure under ithreads,
1304 and a global variable otherwise.
1308 C<Perl_mg_free()> used to leave freed memory accessible via C<SvMAGIC()> on
1309 the scalar. It now updates the linked list to remove each piece of magic
1314 Under ithreads, the regex in C<PL_reg_curpm> is now reference counted. This
1315 eliminates a lot of hackish workarounds to cope with it not being reference
1320 C<Perl_mg_magical()> would sometimes incorrectly turn on C<SvRMAGICAL()>.
1321 This has been fixed.
1325 The I<public> IV and NV flags are now not set if the string value has
1326 trailing "garbage". This behaviour is consistent with not setting the
1327 public IV or NV flags if the value is out of range for the type.
1331 SV allocation tracing has been added to the diagnostics enabled by C<-Dm>.
1332 The tracing can alternatively output via the C<PERL_MEM_LOG> mechanism, if
1333 that was enabled when the F<perl> binary was compiled.
1337 Smartmatch resolution tracing has been added as a new diagnostic. Use C<-DM> to
1342 A new debugging flag C<-DB> now dumps subroutine definitions, leaving
1343 C<-Dx> for its original purpose of dumping syntax trees.
1347 Uses of C<Nullav>, C<Nullcv>, C<Nullhv>, C<Nullop>, C<Nullsv> etc have been
1348 replaced by C<NULL> in the core code, and non-dual-life modules, as C<NULL>
1349 is clearer to those unfamiliar with the core code.
1353 A macro C<MUTABLE_PTR(p)> has been added, which on (non-pedantic) gcc will
1354 not cast away C<const>, returning a C<void *>. Macros C<MUTABLE_SV(av)>,
1355 C<MUTABLE_SV(cv)> etc build on this, casting to C<AV *> etc without
1356 casting away C<const>. This allows proper compile-time auditing of
1357 C<const> correctness in the core, and helped picked up some errors (now
1362 Macros C<mPUSHs()> and C<mXPUSHs()> have been added, for pushing SVs on the
1363 stack and mortalizing them.
1367 Use of the private structure C<mro_meta> has changed slightly. Nothing
1368 outside the core should be accessing this directly anyway.
1372 A new tool, F<Porting/expand-macro.pl> has been added, that allows you
1373 to view how a C preprocessor macro would be expanded when compiled.
1374 This is handy when trying to decode the macro hell that is the perl
1383 Many modules updated from CPAN incorporate new tests.
1384 Several tests that have the potential to hang forever if they fail now
1385 incorporate a "watchdog" functionality that will kill them after a timeout,
1386 which helps ensure that C<make test> and C<make test_harness> run to
1387 completion automatically. (Jerry Hedden).
1389 Some core-specific tests have been added:
1395 Significant cleanups to core tests to ensure that language and
1396 interpreter features are not used before they're tested.
1400 C<make test_porting> now runs a number of important pre-commit checks
1401 which might be of use to anyone working on the Perl core.
1405 F<t/porting/podcheck.t> automatically checks the well-formedness of
1406 POD found in all .pl, .pm and .pod files in the F<MANIFEST>, other than in
1407 dual-lifed modules which are primarily maintained outside the Perl core.
1411 F<t/porting/manifest.t> now tests that all files listed in MANIFEST are present.
1415 F<t/op/while_readdir.t>
1417 Test that a bare readdir in while loop sets $_.
1421 F<t/comp/retainedlines.t>
1423 Check that the debugger can retain source lines from C<eval>.
1427 F<t/io/perlio_fail.t>
1429 Check that bad layers fail.
1433 F<t/io/perlio_leaks.t>
1435 Check that PerlIO layers are not leaking.
1439 F<t/io/perlio_open.t>
1441 Check that certain special forms of open work.
1447 General PerlIO tests.
1453 Check that there is no unexpected interaction between the internal types
1454 C<PVBM> and C<PVGV>.
1458 F<t/mro/package_aliases.t>
1460 Check that mro works properly in the presence of aliased packages.
1466 Tests for C<dbmopen> and C<dbmclose>.
1472 Tests for the interaction of C<index> and threads.
1478 Tests for the interaction of esoteric patterns and threads.
1484 Test that C<qr> doesn't leak.
1488 F<t/op/reg_email_thr.t>
1490 Tests for the interaction of regex recursion and threads.
1494 F<t/op/regexp_qr_embed_thr.t>
1496 Tests for the interaction of patterns with embedded C<qr//> and threads.
1500 F<t/op/regexp_unicode_prop.t>
1502 Tests for Unicode properties in regular expressions.
1506 F<t/op/regexp_unicode_prop_thr.t>
1508 Tests for the interaction of Unicode properties and threads.
1512 F<t/op/reg_nc_tie.t>
1514 Test the tied methods of C<Tie::Hash::NamedCapture>.
1518 F<t/op/reg_posixcc.t>
1520 Check that POSIX character classes behave consistently.
1526 Check that exportable C<re> functions in F<universal.c> work.
1530 F<t/op/setpgrpstack.t>
1532 Check that C<setpgrp> works.
1536 F<t/op/substr_thr.t>
1538 Tests for the interaction of C<substr> and threads.
1544 Check that upgrading and assigning scalars works.
1550 Check that Unicode in the lexer works.
1556 Check that Unicode and C<tie> work.
1560 F<t/comp/final_line_num.t>
1562 See if line numbers are correct at EOF
1566 F<t/comp/form_scope.t>
1568 See if format scoping works
1572 F<t/comp/line_debug.t>
1574 See if C<< @{"_<$file"} >> works
1578 F<t/op/filetest_t.t>
1580 See if -t file test works
1592 Tests malfunctions of utf8 cache
1598 Test unicode \p{} regex constructs
1602 =head2 Testing improvements
1608 It's now possible to override C<PERL5OPT> and friends in F<t/TEST>
1613 =head1 New or Changed Diagnostics
1615 Several new diagnostics, see L<perldiag> for details.
1621 C<Bad plugin affecting keyword '%s'>
1625 C<gmtime(%.0f) too large>
1629 C<Lexing code attempted to stuff non-Latin-1 character into Latin-1 input>
1633 C<Lexing code internal error (%s)>
1637 C<localtime(%.0f) too large>
1641 C<Overloaded dereference did not return a reference>
1645 C<Overloaded qr did not return a REGEXP>
1649 C<Perl_pmflag() is deprecated, and will be removed from the XS API>
1653 New warning category C<illegalproto>
1657 Illegal character in prototype for %s : %s
1658 Prototype after '%c' for %s : %s
1660 have been moved from the C<syntax> top-level warnings category into a new
1661 first-level category, C<illegalproto>. These two warnings are currently the
1662 only ones emitted during parsing of an invalid/illegal prototype, so one
1665 no warnings 'illegalproto';
1667 to suppress only those, but not other syntax-related warnings. Warnings where
1668 prototypes are changed, ignored, or not met are still in the C<prototype>
1669 category as before. (Matt S. Trout)
1673 lvalue attribute ignored after the subroutine has been defined
1675 This new warning is issued when one attempts to mark a subroutine as
1676 lvalue after it has been defined.
1680 warn if C<++> or C<--> are unable to change the value because it's
1681 beyond the limit of representation
1683 This uses a new warnings category: "imprecision".
1687 C<lc>, C<uc>, C<lcfirst>, and C<ucfirst> warn when passed undef.
1691 Show constant in "Useless use of a constant in void context"
1695 Make the new warning report undef constants as undef
1699 Add a new warning, "Prototype after '%s'"
1703 Tweak the "Illegal character in prototype" warning so it's more precise
1704 when reporting illegal characters after _
1708 Correct the unintended interpolation of C<$\> in regex
1712 Make overflow warnings in C<gmtime> and C<localtime> only occur when
1713 warnings are enabled
1717 Improve mro merging error messages.
1719 They are now very similar to those produced by Algorithm::C3.
1723 Amelioration of the error message "Unrecognized character %s in column %d"
1725 Changes the error message to "Unrecognized character %s; marked by E<lt>--
1726 HERE after %sE<lt>-- HERE near column %d". This should make it a little
1727 simpler to spot and correct the suspicious character.
1731 Explicitely point to C<$.> when it causes an uninitialized warning for
1732 ranges in scalar context
1736 C<split> now warns when called in void context
1740 C<printf>-style functions called with too few arguments will now issue the
1741 warning C<"Missing argument in %s"> [perl #71000]
1745 C<panic: sv_chop %s>
1747 This new fatal error occurs when the C routine C<Perl_sv_chop()> was
1748 passed a position that is not within the scalar's string buffer. This
1749 could be caused by buggy XS code, and at this point recovery is not
1754 C<Deep recursion on subroutine "%s">
1756 It is now possible to change the depth threshold for this warning from the
1757 default of 100, by recompiling the F<perl> binary, setting the C
1758 pre-processor macro C<PERL_SUB_DEPTH_WARN> to the desired value.
1762 Perl now properly returns a syntax error instead of segfaulting
1763 if C<each>, C<keys>, or C<values> is used without an argument.
1767 C<tell()> now fails properly if called without an argument and when no
1768 previous file was read.
1770 C<tell()> now returns C<-1>, and sets errno to C<EBADF>, thus restoring
1771 the 5.8.x behaviour.
1775 C<overload> no longer implicitly unsets fallback on repeated 'use
1780 POSIX::strftime() can now handle Unicode characters in the format string.
1784 The Windows select() implementation now supports all empty C<fd_set>s
1789 The "syntax" category was removed from 5 warnings that should only be in
1794 Three fatal C<pack>/C<unpack> error messages have been normalized to
1799 "Unicode character is illegal" has been rephrased to be more accurate
1801 It now reads C<Unicode non-character is illegal in interchange> and the
1802 perldiag documentation has been expanded a bit.
1806 Perl now defaults to issuing a warning if a deprecated language feature
1809 To disable this feature in a given lexical scope, you should use C<no
1810 warnings 'deprecated';> For information about which language features
1811 are deprecated and explanations of various deprecation warnings, please
1816 The following diagnostics have been removed:
1826 C<Can't locate package %s for the parents of %s>
1828 This warning has been removed. In general, it only got produced in
1829 conjunction with other warnings, and removing it allowed an ISA lookup
1830 optimisation to be added.
1834 C<v-string in use/require is non-portable>
1838 =head1 Utility Changes
1846 Now looks in C<include-fixed> too, which is a recent addition to gcc's
1853 No longer incorrectly treats enum values like macros (Daniel Burr).
1855 Now handles C++ style constants (C<//>) properly in enums. (A patch from
1856 Rainer Weikusat was used; Daniel Burr also proposed a similar fix).
1862 C<LVALUE> subroutines now work under the debugger.
1864 The debugger now correctly handles proxy constant subroutines, and
1871 F<perlbug> now uses C<%Module::CoreList::bug_tracker> to print out upstream bug
1874 Where the user names a module that their bug report is about, and we know the
1875 URL for its upstream bug tracker, provide a message to the user explaining
1876 that the core copies the CPAN version directly, and provide the URL for
1877 reporting the bug directly to upstream.
1883 Perl 5.11.0 added a new utility F<perlthanks>, which is a variant of
1884 F<perlbug>, but for sending non-bug-reports to the authors and maintainers
1885 of Perl. Getting nothing but bug reports can become a bit demoralising:
1886 we'll see if this changes things.
1892 No longer reports "Message sent" when it hasn't actually sent the message
1898 Fixed bugs with the match() operator in list context, remove mention of
1903 =head1 Selected Bug Fixes
1909 Ensure that pp_qr returns a new regexp SV each time. Resolves RT #69852.
1911 Instead of returning a(nother) reference to the (pre-compiled) regexp in the
1912 optree, use reg_temp_copy() to create a copy of it, and return a reference to
1913 that. This resolves issues about Regexp::DESTROY not being called in a timely
1914 fashion (the original bug tracked by RT #69852), as well as bugs related to
1915 blessing regexps, and of assigning to regexps, as described in correspondence
1916 added to the ticket.
1918 It transpires that we also need to undo the SvPVX() sharing when ithreads
1919 cloning a Regexp SV, because mother_re is set to NULL, instead of a cloned
1920 copy of the mother_re. This change might fix bugs with regexps and threads in
1921 certain other situations, but as yet neither tests nor bug reports have
1922 indicated any problems, so it might not actually be an edge case that it's
1927 Several compilation errors and segfaults when perl was built with C<-Dmad> were fixed.
1931 Fixes for lexer API changes in 5.11.2 which broke NYTProf's savesrc option.
1935 C<-t> should only return TRUE for file handles connected to a TTY
1937 The Microsoft C version of C<isatty()> returns TRUE for all
1938 character mode devices, including the F</dev/null>-style "nul"
1939 device and printers like "lpt1".
1943 Fixed a regression caused by commit fafafbaf which caused a panic during
1944 parameter passing [perl #70171]
1948 On systems which in-place edits without backup files, -i'*' now works as
1949 the documentation says it does [perl #70802]
1953 Saving and restoring magic flags no longer loses readonly flag.
1957 The malformed syntax C<grep EXPR LIST> (note the missing comma) no longer
1958 causes abrupt and total failure.
1962 Regular expressions compiled with C<qr{}> literals properly set C<$'> when
1967 Using named subroutines with C<sort> should no longer lead to bus errors [perl
1972 Numerous bugfixes catch small issues caused by the recently-added Lexer API.
1976 Smart match against C<@_> sometimes gave false negatives. [perl #71078]
1980 C<$@> may now be assigned a read-only value (without error or busting
1985 C<sort> called recursively from within an active comparison subroutine no
1986 longer causes a bus error if run multiple times. [perl #71076]
1990 Tie::Hash::NamedCapture::* will not abort if passed bad input (RT #71828)
1994 @_ and $_ no longer leak under threads (RT #34342 and #41138, also
1999 C<-I> on shebang line now adds directories in front of @INC
2000 as documented, and as does C<-I> when specified on the command-line.
2004 C<kill> is now fatal when called on non-numeric process identifiers.
2005 Previously, an C<undef> process identifier would be interpreted as a
2006 request to kill process 0, which would terminate the current process
2007 group on POSIX systems. Since process identifiers are always integers,
2008 killing a non-numeric process is now fatal.
2012 5.10.0 inadvertently disabled an optimisation, which caused a measurable
2013 performance drop in list assignment, such as is often used to assign
2014 function parameters from C<@_>. The optimisation has been re-instated, and
2015 the performance regression fixed. (This fix is also present in 5.10.1)
2019 Fixed memory leak on C<while (1) { map 1, 1 }> [RT #53038].
2023 Some potential coredumps in PerlIO fixed [RT #57322,54828].
2027 The debugger now works with lvalue subroutines.
2031 The debugger's C<m> command was broken on modules that defined constants
2036 C<crypt> and string complement could return tainted values for untainted
2037 arguments [RT #59998].
2041 The C<-i>I<.suffix> command-line switch now recreates the file using
2042 restricted permissions, before changing its mode to match the original
2043 file. This eliminates a potential race condition [RT #60904].
2047 On some Unix systems, the value in C<$?> would not have the top bit set
2048 (C<$? & 128>) even if the child core dumped.
2052 Under some circumstances, C<$^R> could incorrectly become undefined
2057 In the XS API, various hash functions, when passed a pre-computed hash where
2058 the key is UTF-8, might result in an incorrect lookup.
2062 XS code including F<XSUB.h> before F<perl.h> gave a compile-time error
2067 C<< $object-E<gt>isa('Foo') >> would report false if the package C<Foo> didn't
2068 exist, even if the object's C<@ISA> contained C<Foo>.
2072 Various bugs in the new-to 5.10.0 mro code, triggered by manipulating
2073 C<@ISA>, have been found and fixed.
2077 Bitwise operations on references could crash the interpreter, e.g.
2078 C<$x=\$y; $x |= "foo"> [RT #54956].
2082 Patterns including alternation might be sensitive to the internal UTF-8
2083 representation, e.g.
2085 my $byte = chr(192);
2086 my $utf8 = chr(192); utf8::upgrade($utf8);
2087 $utf8 =~ /$byte|X}/i; # failed in 5.10.0
2091 Within UTF8-encoded Perl source files (i.e. where C<use utf8> is in
2092 effect), double-quoted literal strings could be corrupted where a C<\xNN>,
2093 C<\0NNN> or C<\N{}> is followed by a literal character with ordinal value
2094 greater than 255 [RT #59908].
2098 C<B::Deparse> failed to correctly deparse various constructs:
2099 C<readpipe STRING> [RT #62428], C<CORE::require(STRING)> [RT #62488],
2100 C<sub foo(_)> [RT #62484].
2104 Using C<setpgrp> with no arguments could corrupt the perl stack.
2108 The block form of C<eval> is now specifically trappable by C<Safe> and
2109 C<ops>. Previously it was erroneously treated like string C<eval>.
2113 In 5.10.0, the two characters C<[~> were sometimes parsed as the smart
2114 match operator (C<~~>) [RT #63854].
2118 In 5.10.0, the C<*> quantifier in patterns was sometimes treated as
2119 C<{0,32767}> [RT #60034, #60464]. For example, this match would fail:
2121 ("ab" x 32768) =~ /^(ab)*$/
2125 C<shmget> was limited to a 32 bit segment size on a 64 bit OS [RT #63924].
2129 Using C<next> or C<last> to exit a C<given> block no longer produces a
2130 spurious warning like the following:
2132 Exiting given via last at foo.pl line 123
2136 On Windows, C<'.\foo'> and C<'..\foo'> were treated differently than
2137 C<'./foo'> and C<'../foo'> by C<do> and C<require> [RT #63492].
2141 Assigning a format to a glob could corrupt the format; e.g.:
2143 *bar=*foo{FORMAT}; # foo format now bad
2147 Attempting to coerce a typeglob to a string or number could cause an
2148 assertion failure. The correct error message is now generated,
2149 C<Can't coerce GLOB to I<$type>>.
2153 Under C<use filetest 'access'>, C<-x> was using the wrong access mode. This
2154 has been fixed [RT #49003].
2158 C<length> on a tied scalar that returned a Unicode value would not be
2159 correct the first time. This has been fixed.
2163 Using an array C<tie> inside in array C<tie> could SEGV. This has been
2168 A race condition inside C<PerlIOStdio_close()> has been identified and
2169 fixed. This used to cause various threading issues, including SEGVs.
2173 In C<unpack>, the use of C<()> groups in scalar context was internally
2174 placing a list on the interpreter's stack, which manifested in various
2175 ways, including SEGVs. This is now fixed [RT #50256].
2179 Magic was called twice in C<substr>, C<\&$x>, C<tie $x, $m> and C<chop>.
2180 These have all been fixed.
2184 A 5.10.0 optimisation to clear the temporary stack within the implicit
2185 loop of C<s///ge> has been reverted, as it turned out to be the cause of
2186 obscure bugs in seemingly unrelated parts of the interpreter [commit
2191 The line numbers for warnings inside C<elsif> are now correct.
2195 The C<..> operator now works correctly with ranges whose ends are at or
2196 close to the values of the smallest and largest integers.
2200 C<binmode STDIN, ':raw'> could lead to segmentation faults on some platforms.
2201 This has been fixed [RT #54828].
2205 An off-by-one error meant that C<index $str, ...> was effectively being
2206 executed as C<index "$str\0", ...>. This has been fixed [RT #53746].
2210 Various leaks associated with named captures in regexes have been fixed
2215 A weak reference to a hash would leak. This was affecting C<DBI>
2220 Using (?|) in a regex could cause a segfault [RT #59734].
2224 Use of a UTF-8 C<tr//> within a closure could cause a segfault [RT #61520].
2228 Calling C<Perl_sv_chop()> or otherwise upgrading an SV could result in an
2229 unaligned 64-bit access on the SPARC architecture [RT #60574].
2233 In the 5.10.0 release, C<inc_version_list> would incorrectly list
2234 C<5.10.*> after C<5.8.*>; this affected the C<@INC> search order
2239 In 5.10.0, C<pack "a*", $tainted_value> returned a non-tainted value
2244 In 5.10.0, C<printf> and C<sprintf> could produce the fatal error
2245 C<panic: utf8_mg_pos_cache_update> when printing UTF-8 strings
2250 In the 5.10.0 release, a dynamically created C<AUTOLOAD> method might be
2251 missed (method cache issue) [RT #60220,60232].
2255 In the 5.10.0 release, a combination of C<use feature> and C<//ee> could
2256 cause a memory leak [RT #63110].
2260 C<-C> on the shebang (C<#!>) line is once more permitted if it is also
2261 specified on the command line. C<-C> on the shebang line used to be a
2262 silent no-op I<if> it was not also on the command line, so perl 5.10.0
2263 disallowed it, which broke some scripts. Now perl checks whether it is
2264 also on the command line and only dies if it is not [RT #67880].
2268 In 5.10.0, certain types of re-entrant regular expression could crash,
2269 or cause the following assertion failure [RT #60508]:
2271 Assertion rx->sublen >= (s - rx->subbeg) + i failed
2275 Previously missing files from Unicode 5.1 Character Database are now included.
2279 C<TMPDIR> is now honored when opening an anonymous temporary file
2283 =head1 Platform Specific Changes
2285 =head2 New Platforms
2291 Patches from the Haiku maintainers have been merged in. Perl should now
2296 Perl should now build on MirOS BSD.
2301 =head2 Discontinued Platforms
2307 Support for Apollo DomainOS was removed in Perl 5.11.0
2311 Support for Tenon Intersystems MachTen Unix layer for MacOS Classic was
2312 removed in Perl 5.11.0
2316 Support for Atari MiNT was removed in Perl 5.11.0.
2320 =head2 Updated Platforms
2324 =item Darwin (Mac OS X)
2330 Skip testing the be_BY.CP1131 locale on Darwin 10 (Mac OS X 10.6),
2331 as it's still buggy.
2335 Correct infelicities in the regexp used to identify buggy locales
2336 on Darwin 8 and 9 (Mac OS X 10.4 and 10.5, respectively).
2346 Fix thread library selection [perl #69686]
2356 Initial support for mingw64 is now available
2360 Various bits of Perl's build infrastructure are no longer converted to
2361 win32 line endings at release time. If this hurts you, please report the
2362 problem with the L<perlbug> program included with perl.
2366 Always add a manifest resource to C<perl.exe> to specify the C<trustInfo>
2367 settings for Windows Vista and later. Without this setting Windows
2368 will treat C<perl.exe> as a legacy application and apply various
2369 heuristics like redirecting access to protected file system areas
2370 (like the "Program Files" folder) to the users "VirtualStore"
2371 instead of generating a proper "permission denied" error.
2373 For VC8 and VC9 this manifest setting is automatically generated by
2374 the compiler/linker (together with the binding information for their
2375 respective runtime libraries); for all other compilers we need to
2376 embed the manifest resource explicitly in the external resource file.
2378 This change also requests the Microsoft Common-Controls version 6.0
2379 (themed controls introduced in Windows XP) via the dependency list
2380 in the assembly manifest. For VC8 and VC9 this is specified using the
2381 C</manifestdependency> linker commandline option instead.
2385 Improved message window handling means that C<alarm> and C<kill> messages
2386 will no longer be dropped under race conditions.
2396 Enable IPv6 support on cygwin 1.7 and newer
2406 Make -UDEBUGGING the default on VMS for 5.12.0.
2408 Like it has been everywhere else for ages and ages. Also make
2409 command-line selection of -UDEBUGGING and -DDEBUGGING work in
2410 configure.com; before the only way to turn it off was by saying
2411 no in answer to the interactive question.
2415 The default pipe buffer size on VMS has been updated to 8192 on 64-bit
2420 Reads from the in-memory temporary files of C<PerlIO::scalar> used to fail
2421 if C<$/> was set to a numeric reference (to indicate record-style reads).
2426 VMS now supports C<getgrgid>.
2430 Many improvements and cleanups have been made to the VMS file name handling
2431 and conversion code.
2435 Enabling the C<PERL_VMS_POSIX_EXIT> logical name now encodes a POSIX exit
2436 status in a VMS condition value for better interaction with GNV's bash
2437 shell and other utilities that depend on POSIX exit values. See
2438 L<perlvms/"$?"> for details.
2442 C<File::Copy> now detects Unix compatibility mode on VMS.
2448 Removed F<libbsd> for AIX 5L and 6.1. Only C<flock()> was used from F<libbsd>.
2450 Removed F<libgdbm> for AIX 5L and 6.1. The F<libgdbm> is delivered as an
2451 optional package with the AIX Toolbox. Unfortunately the 64 bit version
2454 Hints changes mean that AIX 4.2 should work again.
2458 On Cygwin we now strip the last number from the DLL. This has been the
2459 behaviour in the cygwin.com build for years. The hints files have been
2465 The hints files now identify the correct threading libraries on FreeBSD 7
2470 We now work around a bizarre preprocessor bug in the Irix 6.5 compiler:
2471 C<cc -E -> unfortunately goes into K&R mode, but C<cc -E file.c> doesn't.
2475 Hints now supports versions 5.*.
2479 Various changes from Stratus have been merged in.
2483 There is now support for Symbian S60 3.2 SDK and S60 5.0 SDK.
2487 =head1 Known Problems
2489 This is a list of some significant unfixed bugs, which are regressions
2490 from either 5.10.0 or 5.8.x.
2496 C<List::Util::first> misbehaves in the presence of a lexical C<$_>
2497 (typically introduced by C<my $_> or implicitly by C<given>). The variable
2498 which gets set for each iteration is the package variable C<$_>, not the
2499 lexical C<$_> [RT #67694].
2501 A similar issue may occur in other modules that provide functions which
2502 take a block as their first argument, like
2504 foo { ... $_ ...} list
2508 The C<charnames> pragma may generate a run-time error when a regex is
2509 interpolated [RT #56444]:
2511 use charnames ':full';
2512 my $r1 = qr/\N{THAI CHARACTER SARA I}/;
2513 "foo" =~ $r1; # okay
2514 "foo" =~ /$r1+/; # runtime error
2516 A workaround is to generate the character outside of the regex:
2518 my $a = "\N{THAI CHARACTER SARA I}";
2523 Some regexes may run much more slowly when run in a child thread compared
2524 with the thread the pattern was compiled into [RT #55600].
2528 Untriaged test crashes on Windows 2000
2530 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.
2534 Known test failures on VMS
2536 Perl 5.11.1 fails a small set of core and CPAN tests as of this release.
2537 With luck, that'll be sorted out for 5.11.2
2541 Known test failures on VMS
2543 Perl 5.11.2 fails a small set of core and CPAN tests as of this
2544 release. With luck, that'll be sorted out for 5.11.3.
2548 =head1 Acknowledgements
2550 Perl 5.12.0 represents approximately two years of development since
2551 Perl 5.10.0 and contains __ lines of changes across ___ files
2552 from __ authors and committers:
2556 Many of the changes included in this version originated in the CPAN
2557 modules included in Perl's core. We're grateful to the entire CPAN
2558 community for helping Perl to flourish.
2560 =head1 Reporting Bugs
2562 If you find what you think is a bug, you might check the articles
2563 recently posted to the comp.lang.perl.misc newsgroup and the perl
2564 bug database at L<http://rt.perl.org/perlbug/>. There may also be
2565 information at L<http://www.perl.org/>, the Perl Home Page.
2567 If you believe you have an unreported bug, please run the B<perlbug>
2568 program included with your release. Be sure to trim your bug down
2569 to a tiny but sufficient test case. Your bug report, along with the
2570 output of C<perl -V>, will be sent off to perlbug@perl.org to be
2571 analyzed by the Perl porting team.
2573 If the bug you are reporting has security implications, which make it
2574 inappropriate to send to a publicly archived mailing list, then please send
2575 it to perl5-security-report@perl.org. This points to a closed subscription
2576 unarchived mailing list, which includes all the core committers, who be able
2577 to help assess the impact of issues, figure out a resolution, and help
2578 co-ordinate the release of patches to mitigate or fix the problem across all
2579 platforms on which Perl is supported. Please only use this address for
2580 security issues in the Perl core, not for modules independently
2581 distributed on CPAN.
2585 The F<Changes> file for an explanation of how to view exhaustive details
2588 The F<INSTALL> file for how to build Perl.
2590 The F<README> file for general stuff.
2592 The F<Artistic> and F<Copying> files for copyright information.