3 perldelta - what is new for perl v5.9.5
7 This document describes differences between the 5.9.4 and the 5.9.5
8 development releases. See L<perl590delta>, L<perl591delta>,
9 L<perl592delta>, L<perl593delta> and L<perl594delta> for the differences
10 between 5.8.0 and 5.9.4.
12 =head1 Incompatible Changes
14 =head2 Tainting and printf
16 When perl is run under taint mode, C<printf()> and C<sprintf()> will now
17 reject any tainted format argument.
19 =head2 Removal of the bytecode compiler and of perlcc
21 C<perlcc>, the byteloader and the supporting modules (B::C, B::CC,
22 B::Bytecode, etc.) are no longer distributed with the perl sources. Those
23 experimental tools have never worked reliably, and, due to the lack of
24 volunteers to keep them in line with the perl interpreter developments, it
25 was decided to remove them instead of shipping a broken version of those.
26 The last version of those modules can be found with perl 5.9.4.
28 However the B compiler framework stays supported in the perl core, as with
29 the more useful modules it has permitted (among others, B::Deparse and
32 =head2 Removal of the JPL
34 The JPL (Java-Perl Linguo) has been removed from the perl sources tarball.
36 =head1 Core Enhancements
38 =head2 Regular expressions
42 =item Recursive Patterns
44 It is now possible to write recursive patterns without using the C<(??{})>
45 construct. This new way is more efficient, and in many cases easier to
48 Each capturing parenthesis can now be treated as an independent pattern
49 that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for
50 "parenthesis number"). For example, the following pattern will match
51 nested balanced angle brackets:
55 ( # start capture buffer 1
56 < # match an opening angle bracket
58 (?> # don't backtrack over the inside of this group
59 [^<>]+ # one or more non angle brackets
60 ) # end non backtracking group
62 (?1) # recurse to bracket 1 and try it again
64 > # match a closing angle bracket
65 ) # end capture buffer one
69 Note, users experienced with PCRE will find that the Perl implementation
70 of this feature differs from the PCRE one in that it is possible to
71 backtrack into a recursed pattern, whereas in PCRE the recursion is
72 atomic or "possessive" in nature. (Yves Orton)
74 =item Named Capture Buffers
76 It is now possible to name capturing parenthesis in a pattern and refer to
77 the captured contents by name. The naming syntax is C<< (?<NAME>....) >>.
78 It's possible to backreference to a named buffer with the C<< \k<NAME> >>
79 syntax. In code, the new magical hash C<%+> can be used to access the
80 contents of the buffers.
82 Thus, to replace all doubled chars, one could write
84 s/(?<letter>.)\k<letter>/$+{letter}/g
86 Only buffers with defined contents will be "visible" in the hash, so
87 it's possible to do something like
89 foreach my $name (keys %+) {
90 print "content of buffer '$name' is $+{$name}\n";
93 Users exposed to the .NET regex engine will find that the perl
94 implementation differs in that the numerical ordering of the buffers
95 is sequential, and not "unnamed first, then named". Thus in the pattern
97 /(A)(?<B>B)(C)(?<D>D)/
99 $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not
100 $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
101 would expect. This is considered a feature. :-) (Yves Orton)
103 =item Possessive Quantifiers
105 Perl now supports the "possessive quantifier" syntax of the "atomic match"
106 pattern. Basically a possessive quantifier matches as much as it can and never
107 gives any back. Thus it can be used to control backtracking. The syntax is
108 similar to non-greedy matching, except instead of using a '?' as the modifier
109 the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
110 quantifiers. (Yves Orton)
112 =item Backtracking control verbs
114 The regex engine now supports a number of special purpose backtrack
115 control verbs: (*COMMIT), (*MARK), (*CUT), (*ERROR), (*FAIL) and
116 (*ACCEPT). See L<perlre> for their descriptions.
120 =head2 The C<_> prototype
122 A new prototype character has been added. C<_> is equivalent to C<$> (it
123 denotes a scalar), but defaults to C<$_> if the corresponding argument
124 isn't supplied. Due to the optional nature of the argument, you can only
125 use it at the end of a prototype, or before a semicolon.
127 This has a small incompatible consequence: the prototype() function has
128 been adjusted to return C<_> for some built-ins in appropriate cases (for
129 example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez)
133 The copy of the Unicode Character Database included in Perl 5.9 has
134 been updated to version 5.0.0.
136 =head1 Modules and Pragmas
138 =head2 New Core Modules
144 C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around
145 C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't
146 included in the perl core; the behaviour of C<Locale::Maketext::Simple>
147 gracefully degrades when the later isn't present.
151 C<Params::Check> implements a generic input parsing/checking mechanism. It
156 =head2 Module changes
162 The C<base> pragma now warns if a class tries to inherit from itself.
166 The C<warnings> pragma doesn't load C<Carp> anymore. That means that code
167 that used C<Carp> routines without having loaded it at compile time might
168 need to be adjusted; typically, the following (faulty) code won't work
169 anymore, and will require parentheses to be added after the function name:
173 Carp::confess "argh";
177 =head1 Utility Changes
181 =head1 Performance Enhancements
183 =head1 Installation and Configuration Improvements
185 =head2 C++ compatibility
187 Efforts have been made to make perl and the core XS modules compilable
188 with various C++ compilers (although the situation is not perfect with
189 some of the compilers on some of the platforms tested.)
193 Perl has been reported to work on MidnightBSD.
195 =head1 Selected Bug Fixes
197 PerlIO::scalar will now prevent writing to read-only scalars.
199 study() never worked for UTF-8 strings, but could lead to false results.
200 It's now a no-op on UTF-8 data. (Yves Orton)
202 =head1 New or Changed Diagnostics
204 =head1 Changed Internals
206 The anonymous hash and array constructors now take 1 op in the optree
207 instead of 3, now that pp_anonhash and pp_anonlist return a reference to
208 an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark).
210 =head1 Known Problems
212 =head2 Platform Specific Problems
214 =head1 Reporting Bugs
216 If you find what you think is a bug, you might check the articles
217 recently posted to the comp.lang.perl.misc newsgroup and the perl
218 bug database at http://rt.perl.org/rt3/ . There may also be
219 information at http://www.perl.org/ , the Perl Home Page.
221 If you believe you have an unreported bug, please run the B<perlbug>
222 program included with your release. Be sure to trim your bug down
223 to a tiny but sufficient test case. Your bug report, along with the
224 output of C<perl -V>, will be sent off to perlbug@perl.org to be
225 analysed by the Perl porting team.
229 The F<Changes> file for exhaustive details on what changed.
231 The F<INSTALL> file for how to build Perl.
233 The F<README> file for general stuff.
235 The F<Artistic> and F<Copying> files for copyright information.