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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 Tainting and printf |
15 | |
16 | When perl is run under taint mode, C<printf()> and C<sprintf()> will now |
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17 | reject any tainted format argument. (Rafael Garcia-SUarez) |
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18 | |
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19 | =head2 Removal of the bytecode compiler and of perlcc |
20 | |
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. |
27 | |
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 |
30 | B::Concise). |
31 | |
32 | =head2 Removal of the JPL |
33 | |
34 | The JPL (Java-Perl Linguo) has been removed from the perl sources tarball. |
35 | |
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36 | =head1 Core Enhancements |
37 | |
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38 | =head2 Regular expressions |
39 | |
40 | =over 4 |
41 | |
42 | =item Recursive Patterns |
43 | |
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 |
46 | read. |
47 | |
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: |
52 | |
53 | / |
54 | ^ # start of line |
55 | ( # start capture buffer 1 |
56 | < # match an opening angle bracket |
57 | (?: # match one of: |
58 | (?> # don't backtrack over the inside of this group |
59 | [^<>]+ # one or more non angle brackets |
60 | ) # end non backtracking group |
61 | | # ... or ... |
62 | (?1) # recurse to bracket 1 and try it again |
63 | )* # 0 or more times. |
64 | > # match a closing angle bracket |
65 | ) # end capture buffer one |
66 | $ # end of line |
67 | /x |
68 | |
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 |
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72 | atomic or "possessive" in nature. (Yves Orton) |
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73 | |
74 | =item Named Capture Buffers |
75 | |
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. |
81 | |
82 | Thus, to replace all doubled chars, one could write |
83 | |
84 | s/(?<letter>.)\k<letter>/$+{letter}/g |
85 | |
86 | Only buffers with defined contents will be "visible" in the hash, so |
87 | it's possible to do something like |
88 | |
89 | foreach my $name (keys %+) { |
90 | print "content of buffer '$name' is $+{$name}\n"; |
91 | } |
92 | |
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 |
96 | |
97 | /(A)(?<B>B)(C)(?<D>D)/ |
98 | |
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 $4 is 'D' that a .NET programmer |
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101 | would expect. This is considered a feature. :-) (Yves Orton) |
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102 | |
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103 | =item Possessive Quantifiers |
104 | |
105 | Perl now supports the "possessive quantifier" syntax of the "atomic match" |
106 | pattern. Basically a possessive quantifier matches as much as it can and never |
107 | gives any back. Thus it can be used to control backtracking. The syntax is |
108 | similar to non-greedy matching, except instead of using a '?' as the modifier |
109 | the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal |
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110 | quantifiers. (Yves Orton) |
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111 | |
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112 | =item Backtracking control verbs |
113 | |
114 | The regex engine now supports a number of special purpose backtrack |
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115 | control verbs: (*COMMIT), (*MARK), (*CUT), (*ERROR), (*FAIL) and |
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116 | (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton) |
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117 | |
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118 | =back |
119 | |
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120 | =head2 The C<_> prototype |
121 | |
122 | A new prototype character has been added. C<_> is equivalent to C<$> (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. |
126 | |
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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) |
130 | |
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131 | =head2 UNITCHECK blocks |
132 | |
133 | C<UNITCHECK>, a new special code block has been introduced, in addition to |
134 | C<BEGIN>, C<CHECK>, C<INIT> and C<END>. |
135 | |
136 | C<CHECK> and C<INIT> blocks, while useful for some specialized purposes, |
137 | are always executed at the transition between the compilation and the |
138 | execution of the main program, and thus are useless whenever code is |
139 | loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed |
140 | just after the unit which defined them has been compiled. See L<perlmod> |
141 | for more information. (Alex Gough) |
142 | |
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143 | =head2 readpipe() is now overridable |
144 | |
145 | The built-in function readpipe() is now overridable. Overriding it permits |
146 | also to override its operator counterpart, C<qx//> (a.k.a. C<``>). (Rafael |
147 | Garcia-Suarez) |
148 | |
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149 | =head2 UCD 5.0.0 |
150 | |
151 | The copy of the Unicode Character Database included in Perl 5.9 has |
152 | been updated to version 5.0.0. |
153 | |
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154 | =head1 Modules and Pragmas |
155 | |
156 | =head2 New Core Modules |
157 | |
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158 | =over 4 |
159 | |
160 | =item * |
161 | |
162 | C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around |
163 | C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't |
164 | included in the perl core; the behaviour of C<Locale::Maketext::Simple> |
165 | gracefully degrades when the later isn't present. |
166 | |
167 | =item * |
168 | |
169 | C<Params::Check> implements a generic input parsing/checking mechanism. It |
170 | is used by CPANPLUS. |
171 | |
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172 | =item * |
173 | |
174 | C<Term::UI> simplifies the task to ask questions at a terminal prompt. |
175 | |
176 | =item * |
177 | |
178 | C<Object::Accessor> provides an interface to create per-object accessors. |
179 | |
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180 | =back |
181 | |
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182 | =head2 Module changes |
183 | |
184 | =over 4 |
185 | |
186 | =item C<base> |
187 | |
188 | The C<base> pragma now warns if a class tries to inherit from itself. |
189 | |
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190 | =item C<warnings> |
191 | |
192 | The C<warnings> pragma doesn't load C<Carp> anymore. That means that code |
193 | that used C<Carp> routines without having loaded it at compile time might |
194 | need to be adjusted; typically, the following (faulty) code won't work |
195 | anymore, and will require parentheses to be added after the function name: |
196 | |
197 | use warnings; |
198 | require Carp; |
199 | Carp::confess "argh"; |
200 | |
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201 | =back |
202 | |
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203 | =head1 Utility Changes |
204 | |
205 | =head1 Documentation |
206 | |
207 | =head1 Performance Enhancements |
208 | |
209 | =head1 Installation and Configuration Improvements |
210 | |
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211 | =head2 C++ compatibility |
212 | |
213 | Efforts have been made to make perl and the core XS modules compilable |
214 | with various C++ compilers (although the situation is not perfect with |
215 | some of the compilers on some of the platforms tested.) |
216 | |
217 | =head2 Ports |
218 | |
219 | Perl has been reported to work on MidnightBSD. |
220 | |
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221 | =head1 Selected Bug Fixes |
222 | |
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223 | PerlIO::scalar will now prevent writing to read-only scalars. Moreover, |
224 | seek() is now supported with PerlIO::scalar-based filehandles, the |
225 | underlying string being zero-filled as needed. |
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226 | |
227 | study() never worked for UTF-8 strings, but could lead to false results. |
228 | It's now a no-op on UTF-8 data. (Yves Orton) |
229 | |
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230 | The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an |
231 | "unsafe" manner (contrary to other signals, that are deferred until the |
232 | perl interpreter reaches a reasonably stable state; see |
233 | L<perlipc/"Deferred Signals (Safe Signals)">). |
234 | |
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235 | When a module or a file is loaded through an @INC-hook, and when this hook |
236 | has set a filename entry in %INC, __FILE__ is now set for this module |
237 | accordingly to the contents of that %INC entry. |
238 | |
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239 | =head1 New or Changed Diagnostics |
240 | |
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241 | =head2 Variable length character upgraded in print |
242 | |
243 | This new UTF-8 warning indicates a situation where a non-Unicode string is |
244 | sent to a UTF-8 output layer, but given what the string contains, encoding |
245 | problems such as double UTF-8 encoding might arise. See L<perldiag>. |
246 | |
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247 | =head1 Changed Internals |
248 | |
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249 | The anonymous hash and array constructors now take 1 op in the optree |
250 | instead of 3, now that pp_anonhash and pp_anonlist return a reference to |
251 | an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark). |
252 | |
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253 | =head1 Known Problems |
254 | |
255 | =head2 Platform Specific Problems |
256 | |
257 | =head1 Reporting Bugs |
258 | |
259 | If you find what you think is a bug, you might check the articles |
260 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
261 | bug database at http://rt.perl.org/rt3/ . There may also be |
262 | information at http://www.perl.org/ , the Perl Home Page. |
263 | |
264 | If you believe you have an unreported bug, please run the B<perlbug> |
265 | program included with your release. Be sure to trim your bug down |
266 | to a tiny but sufficient test case. Your bug report, along with the |
267 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
268 | analysed by the Perl porting team. |
269 | |
270 | =head1 SEE ALSO |
271 | |
272 | The F<Changes> file for exhaustive details on what changed. |
273 | |
274 | The F<INSTALL> file for how to build Perl. |
275 | |
276 | The F<README> file for general stuff. |
277 | |
278 | The F<Artistic> and F<Copying> files for copyright information. |
279 | |
280 | =cut |