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1 | =head1 NAME |
2 | |
3 | perldelta - what is new for perl v5.9.5 |
4 | |
5 | =head1 DESCRIPTION |
6 | |
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. |
11 | |
12 | =head1 Incompatible Changes |
13 | |
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14 | =head2 Removal of the bytecode compiler and of perlcc |
15 | |
16 | C<perlcc>, the byteloader and the supporting modules (B::C, B::CC, |
17 | B::Bytecode, etc.) are no longer distributed with the perl sources. Those |
18 | experimental tools have never worked reliably, and, due to the lack of |
19 | volunteers to keep them in line with the perl interpreter developments, it |
20 | was decided to remove them instead of shipping a broken version of those. |
21 | The last version of those modules can be found with perl 5.9.4. |
22 | |
23 | However the B compiler framework stays supported in the perl core, as with |
24 | the more useful modules it has permitted (among others, B::Deparse and |
25 | B::Concise). |
26 | |
27 | =head2 Removal of the JPL |
28 | |
29 | The JPL (Java-Perl Linguo) has been removed from the perl sources tarball. |
30 | |
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31 | =head1 Core Enhancements |
32 | |
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33 | =head2 Regular expressions |
34 | |
35 | =over 4 |
36 | |
37 | =item Recursive Patterns |
38 | |
39 | It is now possible to write recursive patterns without using the C<(??{})> |
40 | construct. This new way is more efficient, and in many cases easier to |
41 | read. |
42 | |
43 | Each capturing parenthesis can now be treated as an independent pattern |
44 | that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for |
45 | "parenthesis number"). For example, the following pattern will match |
46 | nested balanced angle brackets: |
47 | |
48 | / |
49 | ^ # start of line |
50 | ( # start capture buffer 1 |
51 | < # match an opening angle bracket |
52 | (?: # match one of: |
53 | (?> # don't backtrack over the inside of this group |
54 | [^<>]+ # one or more non angle brackets |
55 | ) # end non backtracking group |
56 | | # ... or ... |
57 | (?1) # recurse to bracket 1 and try it again |
58 | )* # 0 or more times. |
59 | > # match a closing angle bracket |
60 | ) # end capture buffer one |
61 | $ # end of line |
62 | /x |
63 | |
64 | Note, users experienced with PCRE will find that the Perl implementation |
65 | of this feature differs from the PCRE one in that it is possible to |
66 | backtrack into a recursed pattern, whereas in PCRE the recursion is |
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67 | atomic or "possessive" in nature. (Yves Orton) |
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68 | |
69 | =item Named Capture Buffers |
70 | |
71 | It is now possible to name capturing parenthesis in a pattern and refer to |
72 | the captured contents by name. The naming syntax is C<< (?<NAME>....) >>. |
73 | It's possible to backreference to a named buffer with the C<< \k<NAME> >> |
74 | syntax. In code, the new magical hash C<%+> can be used to access the |
75 | contents of the buffers. |
76 | |
77 | Thus, to replace all doubled chars, one could write |
78 | |
79 | s/(?<letter>.)\k<letter>/$+{letter}/g |
80 | |
81 | Only buffers with defined contents will be "visible" in the hash, so |
82 | it's possible to do something like |
83 | |
84 | foreach my $name (keys %+) { |
85 | print "content of buffer '$name' is $+{$name}\n"; |
86 | } |
87 | |
88 | Users exposed to the .NET regex engine will find that the perl |
89 | implementation differs in that the numerical ordering of the buffers |
90 | is sequential, and not "unnamed first, then named". Thus in the pattern |
91 | |
92 | /(A)(?<B>B)(C)(?<D>D)/ |
93 | |
94 | $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not |
95 | $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer |
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96 | would expect. This is considered a feature. :-) (Yves Orton) |
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97 | |
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98 | =item Possessive Quantifiers |
99 | |
100 | Perl now supports the "possessive quantifier" syntax of the "atomic match" |
101 | pattern. Basically a possessive quantifier matches as much as it can and never |
102 | gives any back. Thus it can be used to control backtracking. The syntax is |
103 | similar to non-greedy matching, except instead of using a '?' as the modifier |
104 | the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal |
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105 | quantifiers. (Yves Orton) |
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106 | |
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107 | =item Backtracking control verbs |
108 | |
109 | The regex engine now supports a number of special purpose backtrack |
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110 | control verbs: (*COMMIT), (*MARK), (*CUT), (*ERROR), (*FAIL) and |
111 | (*ACCEPT). See L<perlre> for their descriptions. |
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112 | |
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113 | =back |
114 | |
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115 | =head2 The C<_> prototype |
116 | |
117 | A new prototype character has been added. C<_> is equivalent to C<$> (it |
118 | denotes a scalar), but defaults to C<$_> if the corresponding argument |
119 | isn't supplied. Due to the optional nature of the argument, you can only |
120 | use it at the end of a prototype, or before a semicolon. |
121 | |
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122 | This has a small incompatible consequence: the prototype() function has |
123 | been adjusted to return C<_> for some built-ins in appropriate cases (for |
124 | example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez) |
125 | |
126 | =head2 UCD 5.0.0 |
127 | |
128 | The copy of the Unicode Character Database included in Perl 5.9 has |
129 | been updated to version 5.0.0. |
130 | |
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131 | =head1 Modules and Pragmas |
132 | |
133 | =head2 New Core Modules |
134 | |
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135 | =over 4 |
136 | |
137 | =item * |
138 | |
139 | C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around |
140 | C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't |
141 | included in the perl core; the behaviour of C<Locale::Maketext::Simple> |
142 | gracefully degrades when the later isn't present. |
143 | |
144 | =item * |
145 | |
146 | C<Params::Check> implements a generic input parsing/checking mechanism. It |
147 | is used by CPANPLUS. |
148 | |
149 | =back |
150 | |
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151 | =head2 Module changes |
152 | |
153 | =over 4 |
154 | |
155 | =item C<base> |
156 | |
157 | The C<base> pragma now warns if a class tries to inherit from itself. |
158 | |
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159 | =item C<warnings> |
160 | |
161 | The C<warnings> pragma doesn't load C<Carp> anymore. That means that code |
162 | that used C<Carp> routines without having loaded it at compile time might |
163 | need to be adjusted; typically, the following (faulty) code won't work |
164 | anymore, and will require parentheses to be added after the function name: |
165 | |
166 | use warnings; |
167 | require Carp; |
168 | Carp::confess "argh"; |
169 | |
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170 | =back |
171 | |
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172 | =head1 Utility Changes |
173 | |
174 | =head1 Documentation |
175 | |
176 | =head1 Performance Enhancements |
177 | |
178 | =head1 Installation and Configuration Improvements |
179 | |
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180 | =head2 C++ compatibility |
181 | |
182 | Efforts have been made to make perl and the core XS modules compilable |
183 | with various C++ compilers (although the situation is not perfect with |
184 | some of the compilers on some of the platforms tested.) |
185 | |
186 | =head2 Ports |
187 | |
188 | Perl has been reported to work on MidnightBSD. |
189 | |
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190 | =head1 Selected Bug Fixes |
191 | |
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192 | PerlIO::scalar will now prevent writing to read-only scalars. |
193 | |
194 | study() never worked for UTF-8 strings, but could lead to false results. |
195 | It's now a no-op on UTF-8 data. (Yves Orton) |
196 | |
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197 | =head1 New or Changed Diagnostics |
198 | |
199 | =head1 Changed Internals |
200 | |
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201 | The anonymous hash and array constructors now take 1 op in the optree |
202 | instead of 3, now that pp_anonhash and pp_anonlist return a reference to |
203 | an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark). |
204 | |
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205 | =head1 Known Problems |
206 | |
207 | =head2 Platform Specific Problems |
208 | |
209 | =head1 Reporting Bugs |
210 | |
211 | If you find what you think is a bug, you might check the articles |
212 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
213 | bug database at http://rt.perl.org/rt3/ . There may also be |
214 | information at http://www.perl.org/ , the Perl Home Page. |
215 | |
216 | If you believe you have an unreported bug, please run the B<perlbug> |
217 | program included with your release. Be sure to trim your bug down |
218 | to a tiny but sufficient test case. Your bug report, along with the |
219 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
220 | analysed by the Perl porting team. |
221 | |
222 | =head1 SEE ALSO |
223 | |
224 | The F<Changes> file for exhaustive details on what changed. |
225 | |
226 | The F<INSTALL> file for how to build Perl. |
227 | |
228 | The F<README> file for general stuff. |
229 | |
230 | The F<Artistic> and F<Copying> files for copyright information. |
231 | |
232 | =cut |