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1 | =head1 NAME |
2 | |
3 | perldelta - what's new for perl5.005 |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This document describes differences between the 5.004 release and this one. |
8 | |
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9 | =head1 About the new versioning system |
10 | |
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11 | Perl is now developed on two tracks: a maintenance track that makes |
12 | small, safe updates to released production versions with emphasis on |
13 | compatibility; and a development track that pursues more aggressive |
14 | evolution. Maintenance releases (which should be considered production |
15 | quality) have subversion numbers that run from C<1> to C<49>, and |
16 | development releases (which should be considered "alpha" quality) run |
17 | from C<50> to C<99>. |
18 | |
19 | Perl 5.005 is the combined product of the new dual-track development |
20 | scheme. |
21 | |
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22 | =head1 Incompatible Changes |
23 | |
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24 | =head2 WARNING: This version is not binary compatible with Perl 5.004. |
25 | |
26 | Starting with Perl 5.004_50 there were many deep and far-reaching changes |
27 | to the language internals. If you have dynamically loaded extensions |
28 | that you built under perl 5.003 or 5.004, you can continue to use them |
29 | with 5.004, but you will need to rebuild and reinstall those extensions |
30 | to use them 5.005. See L<INSTALL> for detailed instructions on how to |
31 | upgrade. |
32 | |
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33 | =head2 Default installation structure has changed |
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34 | |
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35 | The new Configure defaults are designed to allow a smooth upgrade from |
36 | 5.004 to 5.005, but you should read L<INSTALL> for a detailed |
37 | discussion of the changes in order to adapt them to your system. |
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38 | |
39 | =head2 Perl Source Compatibility |
40 | |
41 | When none of the experimental features are enabled, there should be |
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42 | very few user-visible Perl source compatibility issues. |
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43 | |
44 | If threads are enabled, then some caveats apply. C<@_> and C<$_> become |
45 | lexical variables. The effect of this should be largely transparent to |
46 | the user, but there are some boundary conditions under which user will |
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47 | need to be aware of the issues. For example, C<local(@_)> results in |
48 | a "Can't localize lexical variable @_ ..." message. This may be enabled |
49 | in a future version. |
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50 | |
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51 | Some new keywords have been introduced. These are generally expected to |
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52 | have very little impact on compatibility. See L<New C<INIT> keyword>, |
53 | L<New C<lock> keyword>, and L<New C<qr//> operator>. |
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54 | |
55 | Certain barewords are now reserved. Use of these will provoke a warning |
56 | if you have asked for them with the C<-w> switch. |
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57 | See L<C<our> is now a reserved word>. |
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58 | |
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59 | =head2 C Source Compatibility |
60 | |
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61 | There have been a large number of changes in the internals to support |
62 | the new features in this release. |
63 | |
64 | =over 4 |
65 | |
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66 | =item Core sources now require ANSI C compiler |
67 | |
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68 | An ANSI C compiler is now B<required> to build perl. See F<INSTALL>. |
69 | |
70 | =item All Perl global variables must now be referenced with an explicit prefix |
71 | |
72 | All Perl global variables that are visible for use by extensions now |
73 | have a C<PL_> prefix. New extensions should C<not> refer to perl globals |
74 | by their unqualified names. To preserve sanity, we provide limited |
75 | backward compatibility for globals that are being widely used like |
76 | C<sv_undef> and C<na> (which should now be written as C<PL_sv_undef>, |
77 | C<PL_na> etc.) |
78 | |
79 | If you find that your XS extension does not compile anymore because a |
80 | perl global is not visible, try adding a C<PL_> prefix to the global |
81 | and rebuild. |
82 | |
83 | It is strongly recommended that all functions in the Perl API that don't |
84 | begin with C<perl> be referenced with a C<Perl_> prefix. The bare function |
85 | names without the C<Perl_> prefix are supported with macros, but this |
86 | support may cease in a future release. |
87 | |
88 | See L<perlguts/API LISTING>. |
89 | |
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90 | =item Enabling threads has source compatibility issues |
91 | |
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92 | Perl built with threading enabled requires extensions to use the new |
93 | C<dTHR> macro to initialize the handle to access per-thread data. |
94 | If you see a compiler error that talks about the variable C<thr> not |
95 | being declared (when building a module that has XS code), you need |
96 | to add C<dTHR;> at the beginning of the block that elicited the error. |
97 | |
98 | The API function C<perl_get_sv("@",FALSE)> should be used instead of |
99 | directly accessing perl globals as C<GvSV(errgv)>. The API call is |
100 | backward compatible with existing perls and provides source compatibility |
101 | with threading is enabled. |
102 | |
103 | See L<API Changes for more information>. |
104 | |
105 | =back |
106 | |
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107 | =head2 Binary Compatibility |
108 | |
109 | This version is NOT binary compatible with older versions. All extensions |
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110 | will need to be recompiled. Further binaries built with threads enabled |
111 | are incompatible with binaries built without. This should largely be |
112 | transparent to the user, as all binary incompatible configurations have |
113 | their own unique architecture name, and extension binaries get installed at |
114 | unique locations. This allows coexistence of several configurations in |
115 | the same directory hierarchy. See F<INSTALL>. |
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116 | |
117 | =head2 Security fixes may affect compatibility |
118 | |
119 | A few taint leaks and taint omissions have been corrected. This may lead |
120 | to "failure" of scripts that used to work with older versions. Compiling |
121 | with -DINCOMPLETE_TAINTS provides a perl with minimal amounts of changes |
122 | to the tainting behavior. But note that the resulting perl will have |
123 | known insecurities. |
124 | |
125 | Oneliners with the C<-e> switch do not create temporary files anymore. |
126 | |
127 | =head2 Relaxed new mandatory warnings introduced in 5.004 |
128 | |
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129 | Many new warnings that were introduced in 5.004 have been made |
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130 | optional. Some of these warnings are still present, but perl's new |
131 | features make them less often a problem. See L<New Diagnostics>. |
132 | |
133 | =head2 Licensing |
134 | |
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135 | Perl has a new Social Contract for contributors. See F<Porting/Contract>. |
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136 | |
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137 | The license included in much of the Perl documentation has changed. |
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138 | See L<perl> and the individual perl man pages listed therein. |
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139 | |
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140 | =head1 Core Changes |
141 | |
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142 | |
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143 | =head2 Threads |
144 | |
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145 | WARNING: Threading is considered an B<experimental> feature. Details of the |
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146 | implementation may change without notice. There are known limitations |
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147 | and some bugs. These are expected to be fixed in future versions. |
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148 | |
149 | See L<README.threads>. |
150 | |
151 | =head2 Compiler |
152 | |
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153 | WARNING: The Compiler and related tools are considered B<experimental>. |
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154 | Features may change without notice, and there are known limitations |
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155 | and bugs. Since the compiler is fully external to perl, the default |
156 | configuration will build and install it. |
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157 | |
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158 | The Compiler produces three different types of transformations of a |
159 | perl program. The C backend generates C code that captures perl's state |
160 | just before execution begins. It eliminates the compile-time overheads |
161 | of the regular perl interpreter, but the run-time performance remains |
162 | comparatively the same. The CC backend generates optimized C code |
163 | equivivalent to the code path at run-time. The CC backend has greater |
164 | potential for big optimizations, but only a few optimizations are |
165 | implemented currently. The Bytecode backend generates a platform |
166 | independent bytecode representation of the interpreter's state |
167 | just before execution. Thus, the Bytecode back end also eliminates |
168 | much of the compilation overhead of the interpreter. |
169 | |
170 | The compiler comes with several valuable utilities. |
171 | |
172 | C<B::Lint> is an experimental module to detect and warn about suspicious |
173 | code, especially the cases that the C<-w> switch does not detect. |
174 | |
175 | C<B::Deparse> can be used to demystify perl code, and understand |
176 | how perl optimizes certain constructs. |
177 | |
178 | C<B::Xref> generates cross reference reports of all definition and use |
179 | of variables, subroutines and formats in a program. |
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180 | |
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181 | C<B::Showlex> show the lexical variables used by a subroutine or file |
182 | at a glance. |
183 | |
184 | C<perlcc> is a simple frontend for compiling perl. |
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185 | |
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186 | See C<ext/B/README>, L<B>, and the respective compiler modules. |
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187 | |
188 | =head2 Regular Expressions |
189 | |
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190 | Perl's regular expression engine has been seriously overhauled, and |
191 | many new constructs are supported. Several bugs have been fixed. |
192 | |
193 | Here is an itemized summary: |
194 | |
195 | =over 4 |
196 | |
197 | =item Many new and improved optimizations |
198 | |
199 | Changes in the RE engine: |
200 | |
201 | Unneeded nodes removed; |
202 | Substrings merged together; |
203 | New types of nodes to process (SUBEXPR)* and similar expressions |
204 | quickly, used if the SUBEXPR has no side effects and matches |
205 | strings of the same length; |
206 | better optimizations by lookup for constant substrings; |
207 | Better search for constants substrings anchored by $ ; |
208 | |
209 | Changes in Perl code using RE engine: |
210 | |
211 | more optimizations to s/longer/short/; |
212 | study() was not working; |
213 | /blah/ may be optimized to an analogue of index() if $& $` $' not seen; |
214 | Unneeded copying of matched-against string removed; |
215 | Only matched part of the string is copying if $` $' were not seen; |
216 | |
217 | =item Many bug fixes |
218 | |
219 | Note that only the major bug fixes are listed here. See F<Changes> for others. |
220 | |
221 | Backtracking might not restore start of $3. |
222 | No feedback if max count for * or + on "complex" subexpression |
223 | was reached, similarly (but at compile time) for {3,34567} |
224 | Primitive restrictions on max count introduced to decrease a |
225 | possibility of a segfault; |
226 | (ZERO-LENGTH)* could segfault; |
227 | (ZERO-LENGTH)* was prohibited; |
228 | Long RE were not allowed; |
229 | /RE/g could skip matches at the same position after a |
230 | zero-length match; |
231 | |
232 | =item New regular expression constructs |
233 | |
234 | The following new syntax elements are supported: |
235 | |
236 | (?<=RE) |
237 | (?<!RE) |
238 | (?{ CODE }) |
239 | (?i-x) |
240 | (?i:RE) |
241 | (?(COND)YES_RE|NO_RE) |
242 | (?>RE) |
243 | \z |
244 | |
245 | =item New operator for precompiled regular expressions |
246 | |
247 | See L<New C<qr//> operator>. |
248 | |
249 | =item Other improvements |
250 | |
251 | better debugging output (possibly with colors), even from non-debugging Perl; |
252 | RE engine code now looks like C, not like assembler; |
253 | behaviour of RE modifiable by `use re' directive; |
254 | Improved documentation; |
255 | Test suite significantly extended; |
256 | Syntax [:^upper:] etc., reserved inside character classes; |
257 | |
258 | =item Incompatible changes |
259 | |
260 | (?i) localized inside enclosing group; |
261 | $( is not interpolated into RE any more; |
262 | /RE/g may match at the same position (with non-zero length) |
263 | after a zero-length match (bug fix). |
264 | |
265 | =back |
266 | |
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267 | See L<perlre> and L<perlop>. |
268 | |
269 | =head2 Improved malloc() |
270 | |
271 | See banner at the beginning of C<malloc.c> for details. |
272 | |
273 | =head2 Quicksort is internally implemented |
274 | |
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275 | Perl now contains its own highly optimized qsort() routine. The new qsort() |
276 | is resistant to inconsistent comparison functions, so Perl's C<sort()> will |
277 | not provoke coredumps any more when given poorly written sort subroutines. |
278 | (Some C library C<qsort()>s that were being used before used to have this |
279 | problem.) In our testing, the new C<qsort()> required the minimal number |
280 | of pair-wise compares on average, among all known C<qsort()> implementations. |
281 | |
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282 | See C<perlfunc/sort>. |
283 | |
284 | =head2 Reliable signals |
285 | |
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286 | Perl's signal handling is susceptible to random crashes, because signals |
287 | arrive asynchronously, and the Perl runtime is not reentrant at arbitrary |
288 | times. |
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289 | |
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290 | However, one experimental implementation of reliable signals is available |
291 | when threads are enabled. See C<Thread::Signal>. Also see F<INSTALL> for |
292 | how to build a Perl capable of threads. |
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293 | |
294 | =head2 Reliable stack pointers |
295 | |
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296 | The internals now reallocate the perl stack only at predictable times. |
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297 | In particular, magic calls never trigger reallocations of the stack, |
298 | because all reentrancy of the runtime is handled using a "stack of stacks". |
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299 | This should improve reliability of cached stack pointers in the internals |
300 | and in XSUBs. |
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301 | |
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302 | =head2 More generous treatment of carriage returns |
303 | |
304 | Perl used to complain if it encountered carriage returns in scripts. Now |
305 | they are treated like whitespace. Literal carriage returns inside |
306 | string literals and here documents are ignored if they are paired with |
307 | newlines, or treated like newlines if they stand alone. This behavior |
308 | means that literal carriage returns in files should be avoided. You |
309 | can get the older, more compatible (but less generous) behavior by |
310 | defining the preprocessor symbol C<TMP_CRLF_PATCH> when building perl. |
311 | |
312 | Note that this doesn't somehow magically allow you to keep all text files |
313 | in DOS format. The generous treatment only applies to files that perl |
314 | itself parses. If your C compiler doesn't allow carriage returns in |
315 | files, you may still be unable to build modules that need a C compiler. |
316 | |
317 | =head2 Memory leaks |
318 | |
319 | C<substr>, C<pos> and C<vec> don't leak memory anymore when used in lvalue |
320 | context. Many small leaks that impacted applications that embed multiple |
321 | interpreters have been fixed. |
322 | |
323 | =head2 Better support for multiple interpreters |
324 | |
325 | The build-time option C<-DMULTIPLICITY> has had many of the details |
326 | reworked. Some previously global variables that should have been |
327 | per-interpreter now are. With care, this allows interpreters to call |
328 | each other. See the C<PerlInterp> extension on CPAN. |
329 | |
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330 | =head2 Behavior of local() on array and hash elements is now well-defined |
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331 | |
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332 | See L<perlsub/"Temporary Values via local()">. |
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333 | |
334 | =head2 C<%!> is transparently tied to the L<Errno> module |
335 | |
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336 | See L<perlvar>, and L<Errno>. |
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337 | |
338 | =head2 Pseudo-hashes are supported |
339 | |
340 | See L<perlref>. |
341 | |
342 | =head2 C<EXPR foreach EXPR> is supported |
343 | |
344 | See L<perlsyn>. |
345 | |
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346 | =head2 Keywords can be globally overridden |
347 | |
348 | See L<perlsub>. |
349 | |
350 | =head2 C<$^E> is meaningful on Win32 |
351 | |
352 | See L<perlvar>. |
353 | |
354 | =head2 C<foreach (1..1000000)> optimized |
355 | |
356 | C<foreach (1..1000000)> is now optimized into a counting loop. It does |
357 | not try to allocate a 1000000-size list anymore. |
358 | |
359 | =head2 C<Foo::> can be used as implicitly quoted package name |
360 | |
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361 | Barewords caused unintuitive behavior when a subroutine with the same |
362 | name as a package happened to be defined. Thus, C<new Foo @args>, |
363 | use the result of the call to C<Foo()> instead of C<Foo> being treated |
364 | as a literal. The recommended way to write barewords in the indirect |
365 | object slot is C<new Foo:: @args>. Note that the method C<new()> is |
366 | called with a first argument of C<Foo>, not C<Foo::> when you do that. |
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367 | |
368 | =head2 C<exists $Foo::{Bar::}> tests existence of a package |
369 | |
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370 | It was impossible to test for the existence of a package without |
371 | actually creating it before. Now C<exists $Foo::{Bar::}> can be |
372 | used to test if the C<Foo::Bar> namespace has been created. |
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373 | |
374 | =head2 Better locale support |
375 | |
376 | See L<perllocale>. |
377 | |
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378 | =head2 Experimental support for 64-bit platforms |
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379 | |
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380 | Perl5 has always had 64-bit support on systems with 64-bit longs. |
381 | Starting with 5.005, the beginnings of experimental support for systems |
382 | with 32-bit long and 64-bit 'long long' integers has been added. |
383 | If you add -DUSE_LONG_LONG to your ccflags in config.sh (or manually |
384 | define it in perl.h) then perl will be built with 'long long' support. |
385 | There will be many compiler warnings, and the resultant perl may not |
386 | work on all systems. There are many other issues related to |
387 | third-party extensions and libraries. This option exists to allow |
388 | people to work on those issues. |
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389 | |
390 | =head2 prototype() returns useful results on builtins |
391 | |
392 | See L<perlfunc/prototype>. |
393 | |
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394 | =head2 Extended support for exception handling |
395 | |
396 | C<die()> now accepts a reference value, and C<$@> gets set to that |
397 | value in exception traps. This makes it possible to propagate |
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398 | exception objects. This is an undocumented B<experimental> feature. |
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399 | |
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400 | =head2 Re-blessing in DESTROY() supported for chaining DESTROY() methods |
401 | |
402 | See L<perlobj/Destructors>. |
403 | |
404 | =head2 All C<printf> format conversions are handled internally |
405 | |
406 | See L<perlfunc/printf>. |
407 | |
408 | =head2 New C<INIT> keyword |
409 | |
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410 | C<INIT> subs are like C<BEGIN> and C<END>, but they get run just before |
411 | the perl runtime begins execution. e.g., the Perl Compiler makes use of |
412 | C<INIT> blocks to initialize and resolve pointers to XSUBs. |
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413 | |
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414 | =head2 New C<lock> keyword |
415 | |
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416 | The C<lock> keyword is the fundamental synchronization primitive |
417 | in threaded perl. When threads are not enabled, it is currently a noop. |
418 | |
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419 | To minimize impact on source compatibility this keyword is "weak", i.e., any |
420 | user-defined subroutine of the same name overrides it, unless a C<use Thread> |
421 | has been seen. |
422 | |
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423 | =head2 New C<qr//> operator |
424 | |
425 | The C<qr//> operator, which is syntactically similar to the other quote-like |
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426 | operators, is used to create precompiled regular expressions. This compiled |
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427 | form can now be explicitly passed around in variables, and interpolated in |
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428 | other regular expressions. See L<perlop>. |
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429 | |
430 | =head2 C<our> is now a reserved word |
431 | |
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432 | Calling a subroutine with the name C<our> will now provoke a warning when |
433 | using the C<-w> switch. |
434 | |
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435 | =head2 Tied arrays are now fully supported |
436 | |
437 | See L<Tie::Array>. |
438 | |
439 | =head2 Tied handles support is better |
440 | |
441 | Several missing hooks have been added. There is also a new base class for |
442 | TIEARRAY implementations. See L<Tie::Array>. |
443 | |
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444 | =head2 4th argument to substr |
445 | |
446 | substr() can now both return and replace in one operation. The optional |
447 | 4th argument is the replacement string. See L<perlfunc/substr>. |
448 | |
449 | =head2 Negative LENGTH argument to splice |
450 | |
451 | Splice() with a negative LENGTH argument now work similar to what the |
452 | LENGTH did for substr(). Previously a negative LENGTH was treated as |
453 | 0. See L<perlfunc/splice>. |
454 | |
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455 | =head2 Magic lvalues are now more magical |
456 | |
457 | When you say something like C<substr($x, 5) = "hi">, the scalar returned |
458 | by substr() is special, in that any modifications to it affect $x. |
459 | (This is called a 'magic lvalue' because an 'lvalue' is something on |
460 | the left side of an assignment.) Normally, this is exactly what you |
461 | would expect to happen, but Perl uses the same magic if you use substr(), |
462 | pos(), or vec() in a context where they might be modified, like taking |
463 | a reference with C<\> or as an argument to a sub that modifies C<@_>. |
464 | In previous versions, this 'magic' only went one way, but now changes |
465 | to the scalar the magic refers to ($x in the above example) affect the |
466 | magic lvalue too. For instance, this code now acts differently: |
467 | |
468 | $x = "hello"; |
469 | sub printit { |
470 | $x = "g'bye"; |
471 | print $_[0], "\n"; |
472 | } |
473 | printit(substr($x, 0, 5)); |
474 | |
475 | In previous versions, this would print "hello", but it now prints "g'bye". |
476 | |
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477 | =head2 E<lt>E<gt> now reads in records |
478 | |
479 | If C<$/> is a referenence to an integer, or a scalar that holds an integer, |
480 | E<lt>E<gt> will read in records instead of lines. For more info, see |
481 | L<perlvar/$/>. |
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482 | |
483 | =head1 Supported Platforms |
484 | |
485 | Configure has many incremental improvements. Site-wide policy for building |
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486 | perl can now be made persistent, via Policy.sh. Configure also records |
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487 | the command-line arguments used in F<config.sh>. |
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488 | |
489 | =head2 New Platforms |
490 | |
491 | BeOS is now supported. See L<README.beos>. |
492 | |
493 | DOS is now supported under the DJGPP tools. See L<README.dos>. |
494 | |
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495 | MPE/iX is now supported. See L<README.mpeix>. |
496 | |
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497 | =head2 Changes in existing support |
498 | |
499 | Win32 support has been vastly enhanced. Support for Perl Object, a C++ |
500 | encapsulation of Perl. GCC and EGCS are now supported on Win32. |
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501 | See F<README.win32>, aka L<perlwin32>. |
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502 | |
503 | VMS configuration system has been rewritten. See L<README.vms>. |
504 | |
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505 | The hints files for most Unix platforms have seen incremental improvements. |
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506 | |
507 | =head1 Modules and Pragmata |
508 | |
509 | =head2 New Modules |
510 | |
511 | =over |
512 | |
513 | =item B |
514 | |
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515 | Perl compiler and tools. See L<B>. |
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516 | |
517 | =item Data::Dumper |
518 | |
519 | A module to pretty print Perl data. See L<Data::Dumper>. |
520 | |
521 | =item Errno |
522 | |
523 | A module to look up errors more conveniently. See L<Errno>. |
524 | |
525 | =item File::Spec |
526 | |
527 | A portable API for file operations. |
528 | |
529 | =item ExtUtils::Installed |
530 | |
531 | Query and manage installed modules. |
532 | |
533 | =item ExtUtils::Packlist |
534 | |
535 | Manipulate .packlist files. |
536 | |
537 | =item Fatal |
538 | |
539 | Make functions/builtins succeed or die. |
540 | |
541 | =item IPC::SysV |
542 | |
543 | Constants and other support infrastructure for System V IPC operations |
544 | in perl. |
545 | |
546 | =item Test |
547 | |
548 | A framework for writing testsuites. |
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549 | |
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550 | =item Tie::Array |
551 | |
552 | Base class for tied arrays. |
553 | |
554 | =item Tie::Handle |
555 | |
556 | Base class for tied handles. |
557 | |
558 | =item Thread |
559 | |
560 | Perl thread creation, manipulation, and support. |
561 | |
562 | =item attrs |
563 | |
564 | Set subroutine attributes. |
565 | |
566 | =item fields |
567 | |
568 | Compile-time class fields. |
569 | |
570 | =item re |
571 | |
572 | Various pragmata to control behavior of regular expressions. |
573 | |
574 | =back |
575 | |
576 | =head2 Changes in existing modules |
577 | |
578 | =over |
579 | |
580 | =item CGI |
581 | |
582 | CGI has been updated to version 2.42. |
583 | |
584 | =item POSIX |
585 | |
586 | POSIX now has its own platform-specific hints files. |
587 | |
588 | =item DB_File |
589 | |
590 | DB_File supports version 2.x of Berkeley DB. See C<ext/DB_File/Changes>. |
591 | |
592 | =item MakeMaker |
593 | |
594 | MakeMaker now supports writing empty makefiles, provides a way to |
595 | specify that site umask() policy should be honored. There is also |
596 | better support for manipulation of .packlist files, and getting |
597 | information about installed modules. |
598 | |
7ea97eb9 |
599 | Extensions that have both architecture-dependent and |
600 | architecture-independent files are now always installed completely in |
601 | the architecture-dependent locations. Previously, the shareable parts |
602 | were shared both across architectures and across perl versions and were |
603 | therefore liable to be overwritten with newer versions that might have |
604 | subtle incompatibilities. |
605 | |
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606 | =item CPAN |
607 | |
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608 | See <perlmodinstall> and L<CPAN>. |
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609 | |
610 | =item Cwd |
611 | |
612 | Cwd::cwd is faster on most platforms. |
613 | |
614 | =item Benchmark |
615 | |
616 | Keeps better time. |
617 | |
618 | =back |
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619 | |
620 | =head1 Utility Changes |
621 | |
637e9122 |
622 | C<h2ph> and related utilities have been vastly overhauled. |
623 | |
624 | C<perlcc>, a new experimental front end for the compiler is available. |
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625 | |
637e9122 |
626 | The crude GNU C<configure> emulator is now called C<configure.gnu> to |
627 | avoid trampling on C<Configure> under case-insensitive filesystems. |
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628 | |
637e9122 |
629 | C<perldoc> used to be rather slow. The slower features are now optional. |
630 | In particular, case-insensitive searches need the C<-i> switch, and |
631 | recursive searches need C<-r>. You can set these switches in the |
632 | C<PERLDOC> environment variable to get the old behavior. |
7ea97eb9 |
633 | |
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634 | =head1 Documentation Changes |
635 | |
429b3afa |
636 | Config.pm now has a glossary of variables. |
637 | |
9cde0e7f |
638 | F<Porting/patching.pod> has detailed instructions on how to create and |
429b3afa |
639 | submit patches for perl. |
640 | |
9cde0e7f |
641 | L<perlport> specifies guidelines on how to write portably. |
642 | |
643 | L<perlmodinstall> describes how to fetch and install modules from C<CPAN> |
644 | sites. |
645 | |
646 | Some more Perl traps are documented now. See L<perltrap>. |
647 | |
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648 | =head1 New Diagnostics |
649 | |
650 | =over |
651 | |
652 | =item Ambiguous call resolved as CORE::%s(), qualify as such or use & |
653 | |
654 | (W) A subroutine you have declared has the same name as a Perl keyword, |
655 | and you have used the name without qualification for calling one or the |
656 | other. Perl decided to call the builtin because the subroutine is |
657 | not imported. |
658 | |
659 | To force interpretation as a subroutine call, either put an ampersand |
660 | before the subroutine name, or qualify the name with its package. |
661 | Alternatively, you can import the subroutine (or pretend that it's |
662 | imported with the C<use subs> pragma). |
663 | |
664 | To silently interpret it as the Perl operator, use the C<CORE::> prefix |
665 | on the operator (e.g. C<CORE::log($x)>) or by declaring the subroutine |
666 | to be an object method (see L<attrs>). |
667 | |
668 | =item Bad index while coercing array into hash |
669 | |
670 | (F) The index looked up in the hash found as the 0'th element of a |
671 | pseudo-hash is not legal. Index values must be at 1 or greater. |
672 | See L<perlref>. |
673 | |
674 | =item Bareword "%s" refers to nonexistent package |
675 | |
676 | (W) You used a qualified bareword of the form C<Foo::>, but |
677 | the compiler saw no other uses of that namespace before that point. |
678 | Perhaps you need to predeclare a package? |
679 | |
680 | =item Can't call method "%s" on an undefined value |
681 | |
682 | (F) You used the syntax of a method call, but the slot filled by the |
683 | object reference or package name contains an undefined value. |
684 | Something like this will reproduce the error: |
685 | |
686 | $BADREF = 42; |
687 | process $BADREF 1,2,3; |
688 | $BADREF->process(1,2,3); |
689 | |
690 | =item Can't coerce array into hash |
691 | |
692 | (F) You used an array where a hash was expected, but the array has no |
693 | information on how to map from keys to array indices. You can do that |
694 | only with arrays that have a hash reference at index 0. |
695 | |
696 | =item Can't goto subroutine from an eval-string |
697 | |
698 | (F) The "goto subroutine" call can't be used to jump out of an eval "string". |
699 | (You can use it to jump out of an eval {BLOCK}, but you probably don't want to.) |
700 | |
0ebe0038 |
701 | =item Can't localize pseudo-hash element |
702 | |
703 | (F) You said something like C<local $ar-E<gt>{'key'}>, where $ar is |
704 | a reference to a pseudo-hash. That hasn't been implemented yet, but |
705 | you can get a similar effect by localizing the corresponding array |
706 | element directly -- C<local $ar-E<gt>[$ar-E<gt>[0]{'key'}]>. |
707 | |
429b3afa |
708 | =item Can't use %%! because Errno.pm is not available |
709 | |
710 | (F) The first time the %! hash is used, perl automatically loads the |
711 | Errno.pm module. The Errno module is expected to tie the %! hash to |
712 | provide symbolic names for C<$!> errno values. |
713 | |
429b3afa |
714 | =item Cannot find an opnumber for "%s" |
715 | |
716 | (F) A string of a form C<CORE::word> was given to prototype(), but |
717 | there is no builtin with the name C<word>. |
718 | |
719 | =item Character class syntax [. .] is reserved for future extensions |
720 | |
721 | (W) Within regular expression character classes ([]) the syntax beginning |
722 | with "[." and ending with ".]" is reserved for future extensions. |
723 | If you need to represent those character sequences inside a regular |
724 | expression character class, just quote the square brackets with the |
725 | backslash: "\[." and ".\]". |
726 | |
727 | =item Character class syntax [: :] is reserved for future extensions |
728 | |
729 | (W) Within regular expression character classes ([]) the syntax beginning |
730 | with "[:" and ending with ":]" is reserved for future extensions. |
731 | If you need to represent those character sequences inside a regular |
732 | expression character class, just quote the square brackets with the |
733 | backslash: "\[:" and ":\]". |
734 | |
735 | =item Character class syntax [= =] is reserved for future extensions |
736 | |
737 | (W) Within regular expression character classes ([]) the syntax |
738 | beginning with "[=" and ending with "=]" is reserved for future extensions. |
739 | If you need to represent those character sequences inside a regular |
740 | expression character class, just quote the square brackets with the |
741 | backslash: "\[=" and "=\]". |
742 | |
743 | =item %s: Eval-group in insecure regular expression |
744 | |
745 | (F) Perl detected tainted data when trying to compile a regular expression |
746 | that contains the C<(?{ ... })> zero-width assertion, which is unsafe. |
747 | See L<perlre/(?{ code })>, and L<perlsec>. |
748 | |
749 | =item %s: Eval-group not allowed, use re 'eval' |
750 | |
751 | (F) A regular expression contained the C<(?{ ... })> zero-width assertion, |
752 | but that construct is only allowed when the C<use re 'eval'> pragma is |
753 | in effect. See L<perlre/(?{ code })>. |
754 | |
755 | =item %s: Eval-group not allowed at run time |
756 | |
757 | (F) Perl tried to compile a regular expression containing the C<(?{ ... })> |
758 | zero-width assertion at run time, as it would when the pattern contains |
759 | interpolated values. Since that is a security risk, it is not allowed. |
760 | If you insist, you may still do this by explicitly building the pattern |
761 | from an interpolated string at run time and using that in an eval(). |
762 | See L<perlre/(?{ code })>. |
763 | |
764 | =item Explicit blessing to '' (assuming package main) |
765 | |
766 | (W) You are blessing a reference to a zero length string. This has |
767 | the effect of blessing the reference into the package main. This is |
768 | usually not what you want. Consider providing a default target |
769 | package, e.g. bless($ref, $p or 'MyPackage'); |
770 | |
771 | =item Illegal hex digit ignored |
772 | |
773 | (W) You may have tried to use a character other than 0 - 9 or A - F in a |
774 | hexadecimal number. Interpretation of the hexadecimal number stopped |
775 | before the illegal character. |
776 | |
777 | =item No such array field |
778 | |
779 | (F) You tried to access an array as a hash, but the field name used is |
780 | not defined. The hash at index 0 should map all valid field names to |
781 | array indices for that to work. |
782 | |
783 | =item No such field "%s" in variable %s of type %s |
784 | |
785 | (F) You tried to access a field of a typed variable where the type |
786 | does not know about the field name. The field names are looked up in |
787 | the %FIELDS hash in the type package at compile time. The %FIELDS hash |
788 | is usually set up with the 'fields' pragma. |
789 | |
790 | =item Out of memory during ridiculously large request |
791 | |
792 | (F) You can't allocate more than 2^31+"small amount" bytes. This error |
793 | is most likely to be caused by a typo in the Perl program. e.g., C<$arr[time]> |
794 | instead of C<$arr[$time]>. |
795 | |
796 | =item Range iterator outside integer range |
797 | |
798 | (F) One (or both) of the numeric arguments to the range operator ".." |
799 | are outside the range which can be represented by integers internally. |
800 | One possible workaround is to force Perl to use magical string |
801 | increment by prepending "0" to your numbers. |
802 | |
803 | =item Recursive inheritance detected while looking for method '%s' in package '%s' |
804 | |
805 | (F) More than 100 levels of inheritance were encountered while invoking a |
806 | method. Probably indicates an unintended loop in your inheritance hierarchy. |
807 | |
808 | =item Reference found where even-sized list expected |
809 | |
810 | (W) You gave a single reference where Perl was expecting a list with |
811 | an even number of elements (for assignment to a hash). This |
812 | usually means that you used the anon hash constructor when you meant |
813 | to use parens. In any case, a hash requires key/value B<pairs>. |
814 | |
815 | %hash = { one => 1, two => 2, }; # WRONG |
816 | %hash = [ qw/ an anon array / ]; # WRONG |
817 | %hash = ( one => 1, two => 2, ); # right |
818 | %hash = qw( one 1 two 2 ); # also fine |
819 | |
820 | =item Undefined value assigned to typeglob |
821 | |
822 | (W) An undefined value was assigned to a typeglob, a la C<*foo = undef>. |
823 | This does nothing. It's possible that you really mean C<undef *foo>. |
824 | |
825 | =item Use of reserved word "%s" is deprecated |
826 | |
827 | (D) The indicated bareword is a reserved word. Future versions of perl |
828 | may use it as a keyword, so you're better off either explicitly quoting |
829 | the word in a manner appropriate for its context of use, or using a |
830 | different name altogether. The warning can be suppressed for subroutine |
831 | names by either adding a C<&> prefix, or using a package qualifier, |
832 | e.g. C<&our()>, or C<Foo::our()>. |
833 | |
834 | =item perl: warning: Setting locale failed. |
835 | |
836 | (S) The whole warning message will look something like: |
837 | |
838 | perl: warning: Setting locale failed. |
839 | perl: warning: Please check that your locale settings: |
840 | LC_ALL = "En_US", |
841 | LANG = (unset) |
842 | are supported and installed on your system. |
843 | perl: warning: Falling back to the standard locale ("C"). |
844 | |
845 | Exactly what were the failed locale settings varies. In the above the |
846 | settings were that the LC_ALL was "En_US" and the LANG had no value. |
847 | This error means that Perl detected that you and/or your system |
848 | administrator have set up the so-called variable system but Perl could |
849 | not use those settings. This was not dead serious, fortunately: there |
850 | is a "default locale" called "C" that Perl can and will use, the |
851 | script will be run. Before you really fix the problem, however, you |
852 | will get the same error message each time you run Perl. How to really |
853 | fix the problem can be found in L<perllocale> section B<LOCALE PROBLEMS>. |
854 | |
855 | =back |
856 | |
857 | |
858 | =head1 Obsolete Diagnostics |
859 | |
860 | =over |
6cc33c6d |
861 | |
429b3afa |
862 | =item Can't mktemp() |
863 | |
864 | (F) The mktemp() routine failed for some reason while trying to process |
865 | a B<-e> switch. Maybe your /tmp partition is full, or clobbered. |
866 | |
867 | =item Can't write to temp file for B<-e>: %s |
868 | |
869 | (F) The write routine failed for some reason while trying to process |
870 | a B<-e> switch. Maybe your /tmp partition is full, or clobbered. |
871 | |
872 | =item Cannot open temporary file |
873 | |
874 | (F) The create routine failed for some reason while trying to process |
875 | a B<-e> switch. Maybe your /tmp partition is full, or clobbered. |
876 | |
429b3afa |
877 | =back |
878 | |
01784f0d |
879 | =head1 BUGS |
880 | |
881 | If you find what you think is a bug, you might check the headers of |
882 | recently posted articles in the comp.lang.perl.misc newsgroup. |
883 | There may also be information at http://www.perl.com/perl/, the Perl |
884 | Home Page. |
885 | |
886 | If you believe you have an unreported bug, please run the B<perlbug> |
887 | program included with your release. Make sure you trim your bug down |
888 | to a tiny but sufficient test case. Your bug report, along with the |
889 | output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be |
890 | analysed by the Perl porting team. |
891 | |
892 | =head1 SEE ALSO |
893 | |
894 | The F<Changes> file for exhaustive details on what changed. |
895 | |
896 | The F<INSTALL> file for how to build Perl. |
897 | |
898 | The F<README> file for general stuff. |
899 | |
900 | The F<Artistic> and F<Copying> files for copyright information. |
901 | |
902 | =head1 HISTORY |
429b3afa |
903 | |
9cde0e7f |
904 | Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions |
905 | from The Perl Porters. |
906 | |
907 | Send omissions or corrections to <F<perlbug@perl.com>>. |
908 | |
429b3afa |
909 | =cut |