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1=head1 NAME
2
40b7eeef 3perldelta - what's new for perl v5.6 (as of v5.005_64)
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4
5=head1 DESCRIPTION
6
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7This is an unsupported alpha release, meant for intrepid Perl developers
8only. The included sources may not even build correctly on some platforms.
9Subscribing to perl5-porters is the best way to monitor and contribute
10to the progress of development releases (see www.perl.org for info).
11
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12This document describes differences between the 5.005 release and this one.
13
14=head1 Incompatible Changes
15
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16=head2 Perl Source Incompatibilities
17
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18Beware that any new warnings that have been added or old ones
19that have been enhanced are B<not> considered incompatible changes.
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20
21Since all new warnings must be explicitly requested via the C<-w>
22switch or the C<warnings> pragma, it is ultimately the programmer's
23responsibility to ensure that warnings are enabled judiciously.
e02fdbd2 24
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25=over 4
26
7d30b5c4 27=item CHECK is a new keyword
4f25aa18 28
40b7eeef 29In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
7d30b5c4 30subroutines named C<CHECK> are now special. These are queued up during
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31compilation and behave similar to END blocks, except they are called at
32the end of compilation rather than at the end of execution. They cannot
33be called directly.
4f25aa18 34
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35=item Treatment of list slices of undef has changed
36
37When taking a slice of a literal list (as opposed to a slice of
38an array or hash), Perl used to return an empty list if the
39result happened to be composed of all undef values.
40
41The new behavior is to produce an empty list if (and only if)
42the original list was empty. Consider the following example:
43
44 @a = (1,undef,undef,2)[2,1,2];
45
46The old behavior would have resulted in @a having no elements.
47The new behavior ensures it has three undefined elements.
48
49Note in particular that the behavior of slices of the following
50cases remains unchanged:
51
52 @a = ()[1,2];
53 @a = (getpwent)[7,0];
54 @a = (anything_returning_empty_list())[2,1,2];
55 @a = @b[2,1,2];
56 @a = @c{'a','b','c'};
57
58See L<perldata>.
59
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60=item Possibly changed pseudo-random number generator
61
62In 5.005_0x and earlier, perl's rand() function used the C library
63rand(3) function. As of 5.005_52, Configure tests for drand48(),
64random(), and rand() (in that order) and picks the first one it finds.
65Perl programs that depend on reproducing a specific set of pseudo-random
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66numbers will now likely produce different output. You can use
67C<sh Configure -Drandfunc=rand> to obtain the old behavior.
757edf6f 68
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69=item Hashing function for hash keys has changed
70
71Perl hashes are not order preserving. The apparently random order
72encountered when iterating on the contents of a hash is determined
73by the hashing algorithm used. To improve the distribution of lower
74bits in the hashed value, the algorithm has changed slightly as of
755.005_52. When iterating over hashes, this may yield a random order
76that is B<different> from that of previous versions.
77
78=item C<undef> fails on read only values
79
80Using the C<undef> operator on a readonly value (such as $1) has
81the same effect as assigning C<undef> to the readonly value--it
82throws an exception.
83
84=item Close-on-exec bit may be set on pipe() handles
85
86On systems that support a close-on-exec flag on filehandles, the
87flag will be set for any handles created by pipe(), if that is
88warranted by the value of $^F that may be in effect. Earlier
89versions neglected to set the flag for handles created with
90pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
91
92=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
93
94Perl 5.004 deprecated the interpretation of C<$$1> and
95similar within interpolated strings to mean C<$$ . "1">,
96but still allowed it.
97
98In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
99
94f7643d 100=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
a5222a85 101
94f7643d 102delete(), each(), values() and hashes in a list context return the actual
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103values in the hash, instead of copies (as they used to in earlier
104versions). Typical idioms for using these constructs copy the
501fbaef 105returned values, but this can make a significant difference when
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106creating references to the returned values.
107
108Keys in the hash are still returned as copies when iterating on
08cd8952 109a hash.
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110
111=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
112
08cd8952 113vec() generates a run-time error if the BITS argument is not
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114a valid power-of-two integer.
115
116=item Text of some diagnostic output has changed
117
118Most references to internal Perl operations in diagnostics
119have been changed to be more descriptive. This may be an
120issue for programs that may incorrectly rely on the exact
121text of diagnostics for proper functioning.
122
123=item C<%@> has been removed
124
125The undocumented special variable C<%@> that used to accumulate
126"background" errors (such as those that happen in DESTROY())
127has been removed, because it could potentially result in memory
128leaks.
129
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130=item Parenthesized not() behaves like a list operator
131
132The C<not> operator now falls under the "if it looks like a function,
133it behaves like a function" rule.
134
135As a result, the parenthesized form can be used with C<grep> and C<map>.
136The following construct used to be a syntax error before, but it works
137as expected now:
138
139 grep not($_), @things;
140
141On the other hand, using C<not> with a literal list slice may not
142work. The following previously allowed construct:
143
144 print not (1,2,3)[0];
145
af365420 146needs to be written with additional parentheses now:
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147
148 print not((1,2,3)[0]);
149
150The behavior remains unaffected when C<not> is not followed by parentheses.
151
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152=item Semantics of bareword prototype C<(*)> have changed
153
154Arguments prototyped as C<*> will now be visible within the subroutine
155as either a simple scalar or as a reference to a typeglob. Perl 5.005
156always coerced simple scalar arguments to a typeglob, which wasn't useful
157in situations where the subroutine must distinguish between a simple
158scalar and a typeglob. See L<perlsub/Prototypes>.
159
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160=back
161
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162=head2 C Source Incompatibilities
163
164=over 4
165
166=item C<PERL_POLLUTE>
167
168Release 5.005 grandfathered old global symbol names by providing preprocessor
87275199 169macros for extension source compatibility. As of release 5.6, these
e02fdbd2 170preprocessor definitions are not available by default. You need to explicitly
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171compile perl with C<-DPERL_POLLUTE> to get these definitions. For
172extensions still using the old symbols, this option can be
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173specified via MakeMaker:
174
14218588 175 perl Makefile.PL POLLUTE=1
e02fdbd2 176
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177=item C<PERL_IMPLICIT_CONTEXT>
178
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179PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
180with one of -Dusethreads, -Dusemultiplicity, or both. It is not
181intended to be enabled by users at this time.
182
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183This new build option provides a set of macros for all API functions
184such that an implicit interpreter/thread context argument is passed to
185every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 186amounts to a macro invocation that actually translates to something like
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187C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
188to not have any significant source compatibility issues, the difference
189between a macro and a real function call will need to be considered.
190
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191This means that there B<is> a source compatibility issue as a result of
192this if your extensions attempt to use pointers to any of the Perl API
193functions.
194
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195Note that the above issue is not relevant to the default build of
196Perl, whose interfaces continue to match those of prior versions
197(but subject to the other options described here).
198
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199See L<perlguts/"The Perl API"> for detailed information on the
200ramifications of building Perl using this option.
201
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202=item C<PERL_POLLUTE_MALLOC>
203
14218588 204Enabling Perl's malloc in release 5.005 and earlier caused
86058a2d 205the namespace of system versions of the malloc family of functions to
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206be usurped by the Perl versions, since by default they used the
207same names.
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208
209Besides causing problems on platforms that do not allow these functions to
210be cleanly replaced, this also meant that the system versions could not
211be called in programs that used Perl's malloc. Previous versions of Perl
14218588 212have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
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213EMBEDMYMALLOC preprocessor definitions.
214
87275199 215As of release 5.6, Perl's malloc family of functions have default names
86058a2d 216distinct from the system versions. You need to explicitly compile perl with
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217C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
218and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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219the default.
220
221Note that these functions do B<not> constitute Perl's memory allocation API.
222See L<perlguts/"Memory Allocation"> for further information about that.
223
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224=back
225
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226=head2 Compatible C Source API Changes
227
228=over
229
230=item C<PATCHLEVEL> is now C<PERL_VERSION>
231
14218588 232The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 233are now available by default from perl.h, and reflect the base revision,
14218588 234patchlevel, and subversion respectively. C<PERL_REVISION> had no
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235prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
236previously available as C<PATCHLEVEL> and C<SUBVERSION>.
237
14218588 238The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 239the numbers have come to stand for in common practice. For compatibility,
14218588 240the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 241included (as required before), so there is no source incompatibility
14218588 242from the change.
cceca5ed 243
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244=item Support for C++ exceptions
245
246change#3386, also needs perlguts documentation
247[TODO - Chip Salzenberg <chip@perlsupport.com>]
248
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249=back
250
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251=head2 Binary Incompatibilities
252
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253In general, the default build of this release is expected to be binary
254compatible for extensions built with the 5.005 release or its maintenance
255versions. However, specific platforms may have broken binary compatibility
256due to changes in the defaults used in hints files. Therefore, please be
257sure to always check the platform-specific README files for any notes to
258the contrary.
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259
260The usethreads or usemultiplicity builds are B<not> binary compatible
261with the corresponding builds in 5.005.
e02fdbd2 262
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263On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
264among others), purely internal symbols such as parser functions and the
265run time opcodes are not exported by default. Perl 5.005 used to export
266all functions irrespective of whether they were considered part of the
267public API or not.
268
269For the full list of public API functions, see L<perlapi>.
270
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271=head1 Installation and Configuration Improvements
272
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273=head2 -Dusethreads means something different
274
275WARNING: Support for threads continues to be an experimental feature.
276Interfaces and implementation are subject to sudden and drastic changes.
277
278The -Dusethreads flag now enables the experimental interpreter-based thread
279support by default. To get the flavor of experimental threads that was in
2805.005 instead, you need to ask for -Duse5005threads.
281
282As of v5.5.640, interpreter-threads support is still lacking a way to
283create new threads from Perl (i.e., C<use Thread;> will not work with
284interpreter threads). C<use Thread;> continues to be available when you
285ask for -Duse5005threads, bugs and all.
286
287=head2 Perl's version numbering has changed
288
289Beginning with Perl version 5.6, the version number convention has been
290changed to a "dotted tuple" scheme that is more commonly found in open
291source projects.
292
293Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
294The next development series following v5.6 will be numbered v5.7.x,
295beginning with v5.7.0, and the next major production release following
296v5.6 will be v5.8.
297
298The v1.2.3 syntax is also now legal in Perl. See L<Support for version tuples>
299for more on that.
300
301To cope with the new versioning system's use of at least three significant
302digits for each version component, the method used for incrementing the
303subversion number has also changed slightly. We assume that versions older
304than v5.6 have been incrementing the subversion component in multiples of
30510. Versions after v5.6 will increment them by 1. Thus, using the new
306notation, 5.005_03 is the same as v5.5.30, and the first maintenance
307version following v5.6 will be v5.6.1, which amounts to a floating point
308value of 5.006_001).
309
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310=head2 New Configure flags
311
312The following new flags may be enabled on the Configure command line
313by running Configure with C<-Dflag>.
314
315 usemultiplicity
16070b82 316 use5005threads
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317
318 uselongdouble
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319 usemorebits
320 uselargefiles
a5222a85 321
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322=head2 -Dusethreads and -Duse64bits now more daring
323
324The Configure options enabling the use of threads and the use of
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32564-bitness are now more daring in the sense that they no more have an
326explicit list of operating systems of known threads/64-bit
67d3893f 327capabilities. In other words: if your operating system has the
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328necessary APIs and datatypes, you should be able just to go ahead and
329use them, for threads by Configure -Dusethreads, and for 64 bits
330either explicitly by Configure -Duse64bits or implicitly if your
331system has 64 bit wide datatypes. See also L<"64-bit support">.
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332
333=head2 Long Doubles
334
335Some platforms have "long doubles", floating point numbers of even
437784d6 336larger range than ordinary "doubles". To enable using long doubles for
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337Perl's scalars, use -Duselongdouble.
338
339=head2 -Dusemorebits
340
341You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
342See also L<"64-bit support">.
343
344=head2 -Duselargefiles
345
346Some platforms support large files, files larger than two gigabytes.
347See L<"Large file support"> for more information.
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348
349=head2 installusrbinperl
350
351You can use "Configure -Uinstallusrbinperl" which causes installperl
352to skip installing perl also as /usr/bin/perl. This is useful if you
353prefer not to modify /usr/bin for some reason or another but harmful
354because many scripts assume to find Perl in /usr/bin/perl.
355
356=head2 SOCKS support
357
358You can use "Configure -Dusesocks" which causes Perl to probe
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359for the SOCKS (v5, not v4) proxy protocol library,
360http://www.socks.nec.com/
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361
362=head2 C<-A> flag
363
364You can "post-edit" the Configure variables using the Configure C<-A>
365flag. The editing happens immediately after the platform specific
366hints files have been processed but before the actual configuration
367process starts. Run C<Configure -h> to find out the full C<-A> syntax.
368
c35dd67d 369=head2 Enhanced Installation Directories
67d3893f 370
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371The installation structure has been enriched to improve the support for
372maintaining multiple versions of perl, to provide locations for
373vendor-supplied modules and scripts, and to ease maintenance of
374locally-added modules and scripts. See the section on Installation
375Directories in the INSTALL file for complete details. For most users
376building and installing from source, the defaults should be fine.
67d3893f 377
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378=head1 Core Changes
379
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380=head2 Unicode and UTF-8 support
381
382Perl can optionally use UTF-8 as its internal representation for character
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383strings. The C<utf8> and C<byte> pragmas are used to control this support
384in the current lexical scope. See L<perlunicode>, L<utf8> and L<byte> for
385more information.
9d73390d 386
16070b82 387=head2 Interpreter cloning, threads, and concurrency
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388
389WARNING: This is an experimental feature in a pre-alpha state. Use
390at your own risk.
391
392Perl 5.005_63 introduces the beginnings of support for running multiple
393interpreters concurrently in different threads. In conjunction with
394the perl_clone() API call, which can be used to selectively duplicate
395the state of any given interpreter, it is possible to compile a
396piece of code once in an interpreter, clone that interpreter
397one or more times, and run all the resulting interpreters in distinct
398threads.
399
400On Windows, this feature is used to emulate fork() at the interpreter
401level. See L<perlfork>.
402
403This feature is still in evolution. It is eventually meant to be used
404to selectively clone a subroutine and data reachable from that
405subroutine in a separate interpreter and run the cloned subroutine
406in a separate thread. Since there is no shared data between the
407interpreters, little or no locking will be needed (unless parts of
408the symbol table are explicitly shared). This is obviously intended
409to be an easy-to-use replacement for the existing threads support.
410
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411Support for cloning interpreters and interpreter concurrency can be
412enabled using the -Dusethreads Configure option (see win32/Makefile for
413how to enable it on Windows.) The resulting perl executable will be
414functionally identical to one that was built with -Dmultiplicity, but
415the perl_clone() API call will only be available in the former.
af365420 416
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417-Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
418Perl source code changes that provide a clear separation between the op tree
419and the data it operates with. The former is considered immutable, and can
420therefore be shared between an interpreter and all of its clones, while the
421latter is considered local to each interpreter, and is therefore copied for
422each clone.
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423
424Note that building Perl with the -Dusemultiplicity Configure option
425is adequate if you wish to run multiple B<independent> interpreters
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426concurrently in different threads. -Dusethreads only provides the
427additional functionality of the perl_clone() API call and other
428support for running B<cloned> interpreters concurrently.
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429
430[XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
431enabled.]
432
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433=head2 Lexically scoped warning categories
434
435You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 436level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 437for details.
9d73390d 438
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439=head2 Lvalue subroutines
440
441WARNING: This is an experimental feature.
442
443change#4081
444[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
d4629d6a 445Tuomas Lukka <lukka@iki.fi>)]
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446
447=head2 "our" declarations
448
449An "our" declaration introduces a value that can be best understood
450as a lexically scoped symbolic alias to a global variable in the
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451package that was current where the variable was declared. This is
452mostly useful as an alternative to the C<vars> pragma, but also provides
453the opportunity to introduce typing and other attributes for such
454variables. See L<perlfunc/our>.
455
456=head2 Support for version tuples
457
458Literals of the form v1.2.3.4 are now parsed as the utf8 string
459C<"\x{1}\x{2}\x{3}\x{4}">. This allows comparing version numbers using
460regular string comparison operators C<eq>, C<ne>, C<lt>, C<gt> etc.
461
462These "dotted tuples" are dual-valued. They are both strings of utf8
463characters, and floating point numbers. Thus v1.2.3.4 has the string
464value C<"\x{1}\x{2}\x{3}\x{4}"> and the numeric value 1.002_003_004.
465As another example, v5.5.640 has the string value C<"\x{5}\x{5}\x{280}">
466(remember 280 hexadecimal is 640 decimal) and the numeric value
4675.005_64.
468
469In conjunction with the new C<$^V> magic variable (which contains
470the perl version in this format), such literals can be used to
471check if you're running a particular version of Perl.
472
473 if ($^V and $^V gt v5.5.640) {
474 # new style version numbers are supported
475 }
476
477C<require> and C<use> also support such literals:
478
479 require v5.6.0; # croak if $^V lt v5.6.0
480 use v5.6.0; # same, but croaks at compile-time
a5222a85 481
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482C<sprintf> and C<printf> support the Perl-specific format type C<%v>
483to print arbitrary strings as dotted tuples.
484
485 printf "v%v", $^V; # prints current version, such as "v5.5.650"
486
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487=head2 Weak references
488
489WARNING: This is an experimental feature.
490
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491In previous versions of Perl, you couldn't cache objects so as
492to allow them to be deleted if the last reference from outside
493the cache is deleted. The reference in the cache would hold a
494reference count on the object and the objects would never be
495destroyed.
496
497Another familiar problem is with circular references. When an
498object references itself, its reference count would never go
499down to zero, and it would not get destroyed until the program
500is about to exit.
501
502Weak references solve this by allowing you to "weaken" any
503reference, that is, make it not count towards the reference count.
504When the last non-weak reference to an object is deleted, the object
505is destroyed and all the weak references to the object are
506automatically undef-ed.
a5222a85 507
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508To use this feature, you need the WeakRef package from CPAN, which
509contains additional documentation.
510
511change#3385, also need perlguts documentation
512[TODO - Tuomas Lukka <lukka@iki.fi>]
a5222a85 513
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514=head2 File globbing implemented internally
515
516WARNING: This is currently an experimental feature. Interfaces and
517implementation are likely to change.
518
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519Perl now uses the File::Glob implementation of the glob() operator
520automatically. This avoids using an external csh process and the
521problems associated with it.
becf2bd3 522
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523=head2 Binary numbers supported
524
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525Binary numbers are now supported as literals, in s?printf formats, and
526C<oct()>:
527
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528 $answer = 0b101010;
529 printf "The answer is: %b\n", oct("0b101010");
4f19785b 530
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531=head2 Some arrows may be omitted in calls through references
532
533Perl now allows the arrow to be omitted in many constructs
534involving subroutine calls through references. For example,
f91101c9 535C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
a5222a85 536This is rather similar to how the arrow may be omitted from
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537C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
538required for C<foo(10)-E<gt>('bar')>.
a5222a85 539
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540=head2 exists() is supported on subroutine names
541
542The exists() builtin now works on subroutine names. A subroutine
543is considered to exist if it has been declared (even if implicitly).
544See L<perlfunc/exists> for examples.
545
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546=head2 exists() and delete() are supported on array elements
547
548The exists() and delete() builtins now work on simple arrays as well.
549The behavior is similar to that on hash elements.
550
8ea97a1e 551exists() can be used to check whether an array element has been
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552initialized. This avoids autovivifying array elements that don't exist.
553If the array is tied, the EXISTS() method in the corresponding tied
554package will be invoked.
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555
556delete() may be used to remove an element from the array and return
557it. The array element at that position returns to its unintialized
558state, so that testing for the same element with exists() will return
559false. If the element happens to be the one at the end, the size of
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560the array also shrinks up to the highest element that tests true for
561exists(), or 0 if none such is found. If the array is tied, the DELETE()
562method in the corresponding tied package will be invoked.
01020589
GS
563
564See L<perlfunc/exists> and L<perlfunc/delete> for examples.
565
5fdc711f
GS
566=head2 syswrite() ease-of-use
567
a5222a85
GS
568The length argument of C<syswrite()> has become optional.
569
b1a9ed4a 570=head2 File and directory handles can be autovivified
a5222a85 571
f91101c9 572Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
b1a9ed4a
GS
573handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
574socket(), and accept()) now autovivify a file or directory handle
575if the handle passed to them is an uninitialized scalar variable. This
576allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
577to be used to create filehandles that will conveniently be closed
578automatically when the scope ends, provided there are no other references
579to them. This largely eliminates the need for typeglobs when opening
580filehandles that must be passed around, as in the following example:
a5222a85
GS
581
582 sub myopen {
583 open my $fh, "@_"
584 or die "Can't open '@_': $!";
585 return $fh;
586 }
587
588 {
589 my $f = myopen("</etc/motd");
590 print <$f>;
591 # $f implicitly closed here
592 }
593
594[TODO - this idiom needs more pod penetration]
6c67e1bb 595
5fdc711f
GS
596=head2 64-bit support
597
9c107f78
JH
598All platforms that have 64-bit integers either (a) natively as longs
599or ints (b) via special compiler flags (c) using long long are able to
600use "quads" (64-integers) as follows:
601
602=over 4
603
a5222a85
GS
604=item *
605
606constants (decimal, hexadecimal, octal, binary) in the code
607
608=item *
9c107f78 609
a5222a85 610arguments to oct() and hex()
9c107f78 611
a5222a85
GS
612=item *
613
614arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
615
616=item *
9c107f78 617
a5222a85 618printed as such
9c107f78 619
a5222a85
GS
620=item *
621
622pack() and unpack() "q" and "Q" formats
623
624=item *
625
626in basic arithmetics: + - * / %
627
628=item *
1fad5d67 629
a5222a85 630vec() (but see the below note about bit arithmetics)
9c107f78
JH
631
632=back
633
634Note that unless you have the case (a) you will have to configure
635and compile Perl using the -Duse64bits Configure flag.
636
3175b8cd 637Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
132ca540
JH
63864-bit clean, they are explictly forced to be 32-bit because of
639tangled backward compatibility issues. This limitation is subject to
640change. Bit arithmetics for bit vector scalars (created by vec()) are
641not limited in their width.
d0ba1bd2 642
2d4389e4 643Last but not least: note that due to Perl's habit of always using
d0ba1bd2
JH
644floating point numbers the quads are still not true integers.
645When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
646-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
647are silently promoted to floating point numbers, after which they will
648start losing precision (their lower digits).
2d4389e4
JH
649
650=head2 Large file support
651
652If you have filesystems that support "large files" (files larger than
aa855319 6532 gigabytes), you may now also be able to create and access them from
249b38c6 654Perl. You have to use Configure -Duselargefiles. Turning on the
822ba51d
JH
655large file support turns on also the 64-bit support on many platforms.
656Beware that unless your filesystem also supports "sparse files" seeking
657to umpteen petabytes may be unadvisable.
2d4389e4 658
eed7fde4
JH
659Note that in addition to requiring a proper file system to do large
660files you may also need to adjust your per-process (or your
661per-system, or per-process-group, or per-user-group) maximum filesize
662limits before running Perl scripts that try to handle large files,
663especially if you intend to write such files.
664
665Finally, in addition to your process/process group maximum filesize
666limits, you may have quota limits on your filesystems that stop you
667(your user id or your user group id) from using large files.
668
669Adjusting your process/user/group/file system/operating system limits
670is outside the scope of Perl core language. For process limits, you
671may try increasing the limits using your shell's limits/limit/ulimit
672command before running Perl. The BSD::Resource extension (not
673included with the standard Perl distribution) may also be of use, it
674offers the getrlimit/setrlimit interface that can be used to adjust
675process resource usage limits, including the maximum filesize limit.
475d79b5 676
aa855319
JH
677=head2 Long doubles
678
679In some systems you may be able to use long doubles to enhance the
822ba51d 680range and precision of your double precision floating point numbers
aa855319
JH
681(that is, Perl's numbers). Use Configure -Duselongdouble to enable
682this support (if it is available).
683
684=head2 "more bits"
685
822ba51d 686You can "Configure -Dusemorebits" to turn on both the 64-bit support
aa855319 687and the long double support.
09bef843 688
43481408
GS
689=head2 Enhanced support for sort() subroutines
690
691Perl subroutines with a prototype of C<($$)> and XSUBs in general can
692now be used as sort subroutines. In either case, the two elements to
af365420 693be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
43481408
GS
694
695For unprototyped sort subroutines, the historical behavior of passing
696the elements to be compared as the global variables $a and $b remains
697unchanged.
698
62c18ce2
GS
699=head2 Better syntax checks on parenthesized unary operators
700
701Expressions such as:
702
14218588
GS
703 print defined(&foo,&bar,&baz);
704 print uc("foo","bar","baz");
705 undef($foo,&bar);
62c18ce2 706
7711098a 707used to be accidentally allowed in earlier versions, and produced
14218588
GS
708unpredictable behaviour. Some produced ancillary warnings
709when used in this way; others silently did the wrong thing.
62c18ce2
GS
710
711The parenthesized forms of most unary operators that expect a single
14218588
GS
712argument now ensure that they are not called with more than one
713argument, making the cases shown above syntax errors. The usual
714behaviour of:
62c18ce2 715
14218588
GS
716 print defined &foo, &bar, &baz;
717 print uc "foo", "bar", "baz";
718 undef $foo, &bar;
62c18ce2
GS
719
720remains unchanged. See L<perlop>.
721
3e3318e7
GS
722=head2 POSIX character class syntax [: :] supported
723
724For example to match alphabetic characters use /[[:alpha:]]/.
725See L<perlre> for details.
726
5a929a98 727=head2 Improved C<qw//> operator
8127e0e3 728
26ef7447
GS
729The C<qw//> operator is now evaluated at compile time into a true list
730instead of being replaced with a run time call to C<split()>. This
14218588
GS
731removes the confusing misbehaviour of C<qw//> in scalar context, which
732had inherited that behaviour from split().
26ef7447
GS
733
734Thus:
735
736 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
737
738now correctly prints "3|a", instead of "2|a".
8127e0e3 739
5a929a98
VU
740=head2 pack() format 'Z' supported
741
742The new format type 'Z' is useful for packing and unpacking null-terminated
743strings. See L<perlfunc/"pack">.
744
4d0c1c44 745=head2 pack() format modifier '!' supported
ee3907e2 746
14218588 747The new format type modifier '!' is useful for packing and unpacking
ee3907e2
JH
748native shorts, ints, and longs. See L<perlfunc/"pack">.
749
f29c64d6
GS
750=head2 pack() and unpack() support counted strings
751
a5222a85 752The template character '/' can be used to specify a counted string
f29c64d6
GS
753type to be packed or unpacked. See L<perlfunc/"pack">.
754
a5222a85
GS
755=head2 Comments in pack() templates
756
757The '#' character in a template introduces a comment up to
758end of the line. This facilitates documentation of pack()
759templates.
760
2b92dfce
GS
761=head2 $^X variables may now have names longer than one character
762
763Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
764error. Now variable names that begin with a control character may be
765arbitrarily long. However, for compatibility reasons, these variables
766I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 767C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
2b92dfce
GS
768than one control character, such as C<${^XY^Z}>, are illegal.
769
14218588
GS
770The old syntax has not changed. As before, `^X' may be either a
771literal control-X character or the two-character sequence `caret' plus
772`X'. When braces are omitted, the variable name stops after the
2b92dfce 773control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 774C<$^X . "YZ"> as before.
2b92dfce
GS
775
776As before, lexical variables may not have names beginning with control
777characters. As before, variables whose names begin with a control
14218588
GS
778character are always forced to be in package `main'. All such variables
779are reserved for future extensions, except those that begin with
09bef843 780C<^_>, which may be used by user programs and are guaranteed not to
14218588 781acquire special meaning in any future version of Perl.
2b92dfce 782
09bef843
SB
783=head2 C<use attrs> implicit in subroutine attributes
784
785Formerly, if you wanted to mark a subroutine as being a method call or
786as requiring an automatic lock() when it is entered, you had to declare
787that with a C<use attrs> pragma in the body of the subroutine.
16070b82 788That can now be accomplished with declaration syntax, like this:
09bef843 789
0120eecf 790 sub mymethod : locked method ;
09bef843 791 ...
16070b82
GS
792 sub mymethod : locked method {
793 ...
794 }
795
796 sub othermethod :locked :method ;
797 ...
798 sub othermethod :locked :method {
09bef843
SB
799 ...
800 }
801
16070b82
GS
802
803(Note how only the first C<:> is mandatory, and whitespace surrounding
804the C<:> is optional.)
805
09bef843
SB
806F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
807with the stubs they provide. See L<attributes>.
808
a5222a85
GS
809=head2 Regular expression improvements
810
811change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
812[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
813
814=head2 Overloading improvements
815
816change#2150
817[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
818
819=head2 open() with more than two arguments
820
821[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
822
823=head2 Support for interpolating named characters
824
825change#4052
826[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
827
08cd8952 828=head2 Experimental support for user-hooks in @INC
a5222a85
GS
829
830[TODO - Ken Fox <kfox@ford.com>]
831
832=head2 C<require> and C<do> may be overridden
833
834C<require> and C<do 'file'> operations may be overridden locally
835by importing subroutines of the same name into the current package
836(or globally by importing them into the CORE::GLOBAL:: namespace).
837Overriding C<require> will also affect C<use>, provided the override
838is visible at compile-time.
839See L<perlsub/"Overriding Built-in Functions">.
840
841=head2 New variable $^C reflects C<-c> switch
842
08cd8952 843C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
844in compile-only mode (i.e. via the C<-c> switch). Since
845BEGIN blocks are executed under such conditions, this variable
846enables perl code to determine whether actions that make sense
847only during normal running are warranted. See L<perlvar>.
848
16070b82
GS
849=head2 New variable $^V contains Perl version in v5.6.0 format
850
851C<$^V> contains the Perl version number as a version tuple that
852can be used in string or numeric comparisons. See
853C<Support for version tuples> for an example.
854
a5222a85
GS
855=head2 Optional Y2K warnings
856
857If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
858it emits optional warnings when concatenating the number 19
859with another number.
860
861This behavior must be specifically enabled when running Configure.
862See L<INSTALL> and L<README.Y2K>.
863
fbad3eb5
GS
864=head1 Significant bug fixes
865
866=head2 E<lt>HANDLEE<gt> on empty files
867
191f2cf3 868With C<$/> set to C<undef>, "slurping" an empty file returns a string of
14218588 869zero length (instead of C<undef>, as it used to) the first time the
191f2cf3
GS
870HANDLE is read after C<$/> is set to C<undef>. Further reads yield
871C<undef>.
fbad3eb5
GS
872
873This means that the following will append "foo" to an empty file (it used
14218588 874to do nothing):
fbad3eb5
GS
875
876 perl -0777 -pi -e 's/^/foo/' empty_file
877
14218588 878The behaviour of:
fbad3eb5
GS
879
880 perl -pi -e 's/^/foo/' empty_file
881
882is unchanged (it continues to leave the file empty).
883
0244c3a4
GS
884=head2 C<eval '...'> improvements
885
886Line numbers (as reflected by caller() and most diagnostics) within
887C<eval '...'> were often incorrect when here documents were involved.
888This has been corrected.
889
890Lexical lookups for variables appearing in C<eval '...'> within
891functions that were themselves called within an C<eval '...'> were
14218588
GS
892searching the wrong place for lexicals. The lexical search now
893correctly ends at the subroutine's block boundary.
0244c3a4
GS
894
895Parsing of here documents used to be flawed when they appeared as
896the replacement expression in C<eval 's/.../.../e'>. This has
897been fixed.
898
a5222a85
GS
899=head2 All compilation errors are true errors
900
901Some "errors" encountered at compile time were by neccessity
902generated as warnings followed by eventual termination of the
903program. This enabled more such errors to be reported in a
904single run, rather than causing a hard stop at the first error
905that was encountered.
906
907The mechanism for reporting such errors has been reimplemented
908to queue compile-time errors and report them at the end of the
909compilation as true errors rather than as warnings. This fixes
08cd8952
GS
910cases where error messages leaked through in the form of warnings
911when code was compiled at run time using C<eval STRING>, and
912also allows such errors to be reliably trapped using __DIE__ hooks.
a5222a85 913
45bc9206
GS
914=head2 Automatic flushing of output buffers
915
14218588
GS
916fork(), exec(), system(), qx//, and pipe open()s now flush buffers
917of all files opened for output when the operation
918was attempted. This mostly eliminates confusing
45bc9206 919buffering mishaps suffered by users unaware of how Perl internally
14218588 920handles I/O.
45bc9206 921
af8c498a
GS
922=head2 Better diagnostics on meaningless filehandle operations
923
924Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
925are compile time errors. Attempting to read from filehandles that
926were opened only for writing will now produce warnings (just as
927writing to read-only filehandles does).
928
a5222a85
GS
929=head2 Where possible, buffered data discarded from duped input filehandle
930
931C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
932was previously read and buffered in C<OLD> before duping the handle.
933On platforms where doing this is allowed, the next read operation
934on C<NEW> will return the same data as the corresponding operation
935on C<OLD>. Formerly, it would have returned the data from the start
936of the following disk block instead.
937
820475bd
GS
938=head2 eof() has the same old magic as <>
939
940C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
941yet been made. C<eof()> has been changed to have a little magic of its
942own, it now opens the C<E<lt>E<gt>> files.
943
a5222a85
GS
944=head2 system(), backticks and pipe open now reflect exec() failure
945
946On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
947etc., are implemented via fork() and exec(). When the underlying
948exec() fails, earlier versions did not report the error properly,
949since the exec() happened to be in a different process.
950
951The child process now communicates with the parent about the
437784d6 952error in launching the external command, which allows these
a5222a85
GS
953constructs to return with their usual error value and set $!.
954
955=head2 Implicitly closed filehandles are safer
956
957Sometimes implicitly closed filehandles (as when they are localized,
958and Perl automatically closes them on exiting the scope) could
959inadvertently set $? or $!. This has been corrected.
960
961=head2 C<(\$)> prototype and C<$foo{a}>
962
963An scalar reference prototype now correctly allows a hash or
964array element in that slot.
965
966=head2 Pseudo-hashes work better
967
968Dereferencing some types of reference values in a pseudo-hash,
f91101c9 969such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
a5222a85
GS
970been corrected.
971
972When applied to a pseudo-hash element, exists() now reports whether
973the specified value exists, not merely if the key is valid.
974
01020589
GS
975delete() now works on pseudo-hashes. When given a pseudo-hash element
976or slice it deletes the values corresponding to the keys (but not the keys
977themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
978
a5222a85
GS
979=head2 C<goto &sub> and AUTOLOAD
980
08cd8952 981The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
982to be autoloaded.
983
984=head2 C<-bareword> allowed under C<use integer>
985
986The autoquoting of barewords preceded by C<-> did not work
987in prior versions when the C<integer> pragma was enabled.
988This has been fixed.
989
990=head2 Boolean assignment operators are legal lvalues
991
992Constructs such as C<($a ||= 2) += 1> are now allowed.
993
994=head2 C<sort $coderef @foo> allowed
995
996sort() did not accept a subroutine reference as the comparison
08cd8952 997function in earlier versions. This is now permitted.
a5222a85
GS
998
999=head2 Failures in DESTROY()
1000
1001When code in a destructor threw an exception, it went unnoticed
1002in earlier versions of Perl, unless someone happened to be
1003looking in $@ just after the point the destructor happened to
1004run. Such failures are now visible as warnings when warnings are
1005enabled.
1006
1007=head2 Locale bugs fixed
54195c32 1008
437784d6 1009printf() and sprintf() previously reset the numeric locale
67d3893f
JH
1010back to the default "C" locale. This has been fixed.
1011
1012Numbers formatted according to the local numeric locale
1013(such as using a decimal comma instead of a decimal dot) caused
1014"isn't numeric" warnings, even while the operations accessing
1015those numbers produced correct results. The warnings are gone.
54195c32 1016
a5222a85
GS
1017=head2 Memory leaks
1018
1019The C<eval 'return sub {...}'> construct could sometimes leak
1020memory. This has been fixed.
1021
1022Operations that aren't filehandle constructors used to leak memory
1023when used on invalid filehandles. This has been fixed.
1024
1025Constructs that modified C<@_> could fail to deallocate values
1026in C<@_> and thus leak memory. This has been corrected.
1027
1028=head2 Spurious subroutine stubs after failed subroutine calls
1029
1030Perl could sometimes create empty subroutine stubs when a
1031subroutine was not found in the package. Such cases stopped
1032later method lookups from progressing into base packages.
1033This has been corrected.
1034
1035=head2 Consistent numeric conversions
1036
1037change#3378,3318
1038[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1039
1040=head2 Taint failures under C<-U>
1041
1042When running in unsafe mode, taint violations could sometimes
1043cause silent failures. This has been fixed.
1044
1045=head2 END blocks and the C<-c> switch
1046
1047Prior versions used to run BEGIN B<and> END blocks when Perl was
1048run in compile-only mode. Since this is typically not the expected
08cd8952 1049behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
1050is used.
1051
7d30b5c4 1052See L<CHECK blocks> for how to run things when the compile phase ends.
a5222a85
GS
1053
1054=head2 Potential to leak DATA filehandles
1055
1056Using the C<__DATA__> token creates an implicit filehandle to
1057the file that contains the token. It is the program's
1058responsibility to close it when it is done reading from it.
1059
1060This caveat is now better explained in the documentation.
1061See L<perldata>.
1062
1063=head2 Diagnostics follow STDERR
1064
1065Diagnostic output now goes to whichever file the C<STDERR> handle
1066is pointing at, instead of always going to the underlying C runtime
1067library's C<stderr>.
1068
1069=head2 Other fixes for better diagnostics
1070
437784d6 1071Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
1072during the global destruction phase.
1073
1074Diagnostics emitted from code running in threads other than the main
1075thread are now accompanied by the thread ID.
1076
1077Embedded null characters in diagnostics now actually show up. They
1078used to truncate the message in prior versions.
1079
1080$foo::a and $foo::b are now exempt from "possible typo" warnings only
1081if sort() is encountered in package foo.
1082
501fbaef 1083Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
1084constructs now generate a warning, since they may take on new
1085semantics in later versions of Perl.
1086
1087=head1 Performance enhancements
1088
1089=head2 Simple sort() using { $a <=> $b } and the like are optimized
1090
08cd8952 1091Many common sort() operations using a simple inlined block are now
a5222a85
GS
1092optimized for faster performance.
1093
1094=head2 Optimized assignments to lexical variables
1095
1096Certain operations in the RHS of assignment statements have been
1097optimized to directly set the lexical variable on the LHS,
1098eliminating redundant copying overheads.
1099
1100=head2 Method lookups optimized
1101
1102[TODO - Chip Salzenberg <chip@perlsupport.com>]
1103
1104=head2 Faster mechanism to invoke XSUBs
1105
1106change#4044,4125
1107[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1108
1109=head2 Perl_malloc() improvements
1110
1111change#4237
1112[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1113
1114=head2 Faster subroutine calls
1115
1116Minor changes in how subroutine calls are handled internally
1117provide marginal improvements in performance.
1118
1119=head1 Platform specific changes
1120
1121=head2 Additional supported platforms
ba8251e8 1122
5fdc711f
GS
1123=over 4
1124
1125=item *
1126
6c67e1bb
TC
1127VM/ESA is now supported.
1128
5fdc711f
GS
1129=item *
1130
ee3907e2
JH
1131Siemens BS2000 is now supported under the POSIX Shell.
1132
1133=item *
1134
2bb14304
JH
1135The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1136extension.
6c67e1bb 1137
5fdc711f
GS
1138=item *
1139
ee3907e2 1140GNU/Hurd is now supported.
6c67e1bb 1141
00ad96e1
JH
1142=item *
1143
1144Rhapsody is now supported.
1145
27806c82
JH
1146=item *
1147
1148EPOC is is now supported (on Psion 5).
1149
5fdc711f
GS
1150=back
1151
a5222a85
GS
1152=head2 DOS
1153
d524f05e
LM
1154=over 4
1155
1156=item *
1157
1158Perl now works with djgpp 2.02 (and 2.03 alpha).
1159
1160=item *
1161
1162Environment variable names are not converted to uppercase any more.
1163
1164=item *
1165
1166Wrong exit code from backticks now fixed.
1167
1168=item *
1169
1170This port is still using its own builtin globbing.
1171
1172=back
a5222a85
GS
1173
1174=head2 OS/2
1175
1176[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1177
1178=head2 VMS
1179
1180[TODO - Charles Bailey <bailey@newman.upenn.edu>]
1181
1182=head2 Win32
1183
1184Site library searches failed to look for ".../site/5.XXX/lib"
1185if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1186
1187When given a pathname that consists only of a drivename, such
1188as C<A:>, opendir() and stat() now use the current working
1189directory for the drive rather than the drive root.
1190
1191The builtin XSUB functions in the Win32:: namespace are
1192documented. See L<Win32>.
1193
1194$^X now contains the full path name of the running executable.
1195
1196A Win32::GetLongPathName() function is provided to complement
1197Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1198
1199POSIX::uname() is supported.
1200
1201system(1,...) now returns true process IDs rather than process
1202handles. kill() accepts any real process id, rather than strictly
1203return values from system(1,...).
1204
1205The C<Shell> module is supported.
1206
883d36a6
GS
1207Rudimentary support for building under command.com in Windows 95
1208has been added.
1209
c39cd008
GS
1210Scripts are read in binary mode by default to allow ByteLoader (and
1211the filter mechanism in general) to work properly. For compatibility,
53129d29
GS
1212the DATA filehandle will be set to text mode if a carriage return is
1213detected at the end of the line containing the __END__ or __DATA__
1214token; if not, the DATA filehandle will be left open in binary mode.
1215Earlier versions always opened the DATA filehandle in text mode.
c39cd008 1216
16070b82 1217The glob() operator is implemented via the L<File::Glob> extension,
8004f2ac 1218which supports glob syntax of the C shell. This increases the flexibility
16070b82
GS
1219of the glob() operator, but there may be compatibility issues for
1220programs that relied on the older globbing syntax. If you want to
1221preserve compatibility with the older syntax, you might want to put
1222a C<use File::DosGlob;> in your program. For details and compatibility
1223information, see L<File::Glob>.
1224
a5222a85
GS
1225[TODO - GSAR]
1226
6c67e1bb
TC
1227=head1 New tests
1228
1229=over 4
1230
09bef843
SB
1231=item lib/attrs
1232
1233Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1234
1235=item lib/io_const
6c67e1bb
TC
1236
1237IO constants (SEEK_*, _IO*).
14218588 1238
09bef843 1239=item lib/io_dir
6c67e1bb
TC
1240
1241Directory-related IO methods (new, read, close, rewind, tied delete).
1242
09bef843 1243=item lib/io_multihomed
6c67e1bb
TC
1244
1245INET sockets with multi-homed hosts.
1246
09bef843 1247=item lib/io_poll
6c67e1bb
TC
1248
1249IO poll().
1250
09bef843 1251=item lib/io_unix
6c67e1bb
TC
1252
1253UNIX sockets.
1254
09bef843
SB
1255=item op/attrs
1256
1257Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1258
6c67e1bb
TC
1259=item op/filetest
1260
1261File test operators.
1262
1263=item op/lex_assign
1264
5fdc711f 1265Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb 1266
afebc493
GS
1267=item op/exists_sub
1268
1269Verify C<exists &sub> operations.
1270
6c67e1bb 1271=back
e02fdbd2 1272
ba8251e8
GS
1273=head1 Modules and Pragmata
1274
3e8c4fa0
JH
1275=head2 Modules
1276
b7d8191e
JH
1277=over 4
1278
09bef843
SB
1279=item attributes
1280
1281While used internally by Perl as a pragma, this module also
1282provides a way to fetch subroutine and variable attributes.
1283See L<attributes>.
1284
a5222a85
GS
1285=item B
1286
501fbaef
GS
1287The Perl Compiler suite has been extensively reworked for this
1288release.
1289
a5222a85
GS
1290[TODO - Vishal Bhatia <vishal@gol.com>,
1291Nick Ing-Simmons <nick@ni-s.u-net.com>]
1292
f29c64d6
GS
1293=item ByteLoader
1294
a5222a85 1295The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1296Perl bytecode. See L<ByteLoader>.
1297
a5222a85
GS
1298=item constant
1299
83763826
GS
1300References can now be used.
1301
1302The new version also allows a leading underscore in constant names, but
1303disallows a double leading underscore (as in "__LINE__"). Some other names
1304are disallowed or warned against, including BEGIN, END, etc. Some names
1305which were forced into main:: used to fail silently in some cases; now they're
1306fatal (outside of main::) and an optional warning (inside of main::).
1307The ability to detect whether a constant had been set with a given name has
1308been added.
1309
1310See L<constant>.
a5222a85
GS
1311
1312=item charnames
1313
1314change#4052
1315[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1316
1317=item Data::Dumper
1318
1319A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1320too deeply into deep data structures. See L<Data::Dumper>.
a5222a85
GS
1321
1322Dumping C<qr//> objects works correctly.
1323
1324=item DB
1325
1326C<DB> is an experimental module that exposes a clean abstraction
1327to Perl's debugging API.
1328
1329=item DB_File
1330
0536e0eb
GS
1331DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1332See C<ext/DB_File/Changes>.
a5222a85 1333
f29c64d6
GS
1334=item Devel::DProf
1335
9e107c59
GS
1336Devel::DProf, a Perl source code profiler has been added. See
1337L<Devel::DProf> and L<dprofpp>.
f29c64d6 1338
b7d8191e
JH
1339=item Dumpvalue
1340
437784d6 1341The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1342
1343=item Benchmark
1344
54e82ce5
GS
1345Overall, Benchmark results exhibit lower average error and better timing
1346accuracy.
1347
868cb350 1348You can now run tests for I<n> seconds instead of guessing the right
14218588
GS
1349number of tests to run: e.g. timethese(-5, ...) will run each
1350code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1351means "for at least 3 CPU seconds". The output format has also
14218588 1352changed. For example:
155776c0 1353
54e82ce5 1354 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1355
1356will now output something like this:
1357
54e82ce5
GS
1358 Benchmark: running a, b, each for at least 5 CPU seconds...
1359 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1360 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1361
1362New features: "each for at least N CPU seconds...", "wallclock secs",
1363and the "@ operations/CPU second (n=operations)".
b7d8191e 1364
54e82ce5
GS
1365timethese() now returns a reference to a hash of Benchmark objects containing
1366the test results, keyed on the names of the tests.
1367
1368timethis() now returns the iterations field in the Benchmark result object
1369instead of 0.
1370
1371timethese(), timethis(), and the new cmpthese() (see below) can also take
1372a format specifier of 'none' to suppress output.
1373
1374A new function countit() is just like timeit() except that it takes a
1375TIME instead of a COUNT.
1376
1377A new function cmpthese() prints a chart comparing the results of each test
1378returned from a timethese() call. For each possible pair of tests, the
1379percentage speed difference (iters/sec or seconds/iter) is shown.
1380
1381For other details, see L<Benchmark>.
a5222a85 1382
f505c983
GS
1383=item Devel::Peek
1384
1385The Devel::Peek module provides access to the internal representation
14218588 1386of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1387
a5222a85
GS
1388=item ExtUtils::MakeMaker
1389
1390change#4135, also needs docs in module pod
1391[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1392
b7d8191e
JH
1393=item Fcntl
1394
1395More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
822ba51d
JH
1396large file (more than 4GB) access Note that the O_LARGEFILE is
1397automatically/transparently added to sysopen() flags if large file
1398support has been configured), Free/Net/OpenBSD locking behaviour flags
1399F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
ca6e1c26
JH
1400O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1401SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1402The chmod()/stat() S_IF* constants and S_IS* functions are available
1403via the C<:mode> tag.
1404
b7d8191e 1405
a5222a85
GS
1406=item File::Compare
1407
1408A compare_text() function has been added, which allows custom
1409comparison functions. See L<File::Compare>.
1410
1411=item File::Find
1412
1413File::Find now works correctly when the wanted() function is either
1414autoloaded or is a symbolic reference.
1415
08cd8952 1416A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1417when pruning top-level directories has been fixed.
1418
81793b90
GS
1419File::Find now also supports several other options to control its
1420behavior. It can follow symbolic links if the C<follow> option is
1421specified. Enabling the C<no_chdir> option will make File::Find skip
1422changing the current directory when walking directories. The C<untaint>
1423flag can be useful when running with taint checks enabled.
1424
1425See L<File::Find>.
1426
becf2bd3
GS
1427=item File::Glob
1428
52bb0670
GS
1429This extension implements BSD-style file globbing. By default,
1430it will also be used for the internal implementation of the glob()
1431operator. See L<File::Glob>.
becf2bd3 1432
f505c983
GS
1433=item File::Spec
1434
1435New methods have been added to the File::Spec module: devnull() returns
19799a22 1436the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1437the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1438to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1439rel2abs(). For compatibility with operating systems that specify volume
1440names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1441have been added.
1442
1443=item File::Spec::Functions
1444
1445The new File::Spec::Functions modules provides a function interface
14218588 1446to the File::Spec module. Allows shorthand
f505c983 1447
14218588 1448 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1449
1450instead of
1451
14218588 1452 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1453
a5222a85
GS
1454=item Getopt::Long
1455
c6edd1b7
GS
1456Getopt::Long licensing has changed to allow the Perl Artistic License
1457as well as the GPL. It used to be GPL only, which got in the way of
1458non-GPL applications that wanted to use Getopt::Long.
1459
1460Getopt::Long encourages the use of Pod::Usage to produce help
1461messages. For example:
1462
1463 use Getopt::Long;
1464 use Pod::Usage;
1465 my $man = 0;
1466 my $help = 0;
1467 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1468 pod2usage(1) if $help;
1469 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1470
1471 __END__
1472
1473 =head1 NAME
1474
1475 sample - Using GetOpt::Long and Pod::Usage
1476
1477 =head1 SYNOPSIS
1478
1479 sample [options] [file ...]
1480
1481 Options:
1482 -help brief help message
1483 -man full documentation
1484
1485 =head1 OPTIONS
1486
1487 =over 8
1488
1489 =item B<-help>
1490
1491 Print a brief help message and exits.
1492
1493 =item B<-man>
1494
1495 Prints the manual page and exits.
1496
1497 =back
1498
1499 =head1 DESCRIPTION
1500
1501 B<This program> will read the given input file(s) and do someting
1502 useful with the contents thereof.
1503
1504 =cut
1505
1506See L<Pod::Usage> for details.
1507
1508A bug that prevented the non-option call-back E<lt>E<gt> from being
1509specified as the first argument has been fixed.
1510
1511To specify the characters E<lt> and E<gt> as option starters, use
1512E<gt>E<lt>. Note, however, that changing option starters is strongly
1513deprecated.
a5222a85
GS
1514
1515=item IO
1516
1517write() and syswrite() will now accept a single-argument
1518form of the call, for consistency with Perl's syswrite().
1519
1520You can now create a TCP-based IO::Socket::INET without forcing
1521a connect attempt. This allows you to configure its options
1522(like making it non-blocking) and then call connect() manually.
1523
1524A bug that prevented the IO::Socket::protocol() accessor
1525from ever returning the correct value has been corrected.
1526
1527=item JPL
1528
1529Java Perl Lingo is now distributed with Perl. See jpl/README
1530for more information.
1531
883d36a6
GS
1532=item lib
1533
1534C<use lib> now weeds out any trailing duplicate entries.
1535C<no lib> removes all named entries.
1536
e16b8f49
WM
1537=item Math::BigInt
1538
437784d6 1539The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
e16b8f49
WM
1540and C<~> are now supported on bigints.
1541
b7d8191e 1542=item Math::Complex
7711098a 1543
14218588 1544The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1545act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e
JH
1546
1547=item Math::Trig
1548
14218588
GS
1549A little bit of radial trigonometry (cylindrical and spherical),
1550radial coordinate conversions, and the great circle distance were added.
b7d8191e 1551
1761cee5 1552=item Pod::Parser, Pod::InputObjects
d4629d6a 1553
1761cee5
JH
1554Pod::Parser is a base class for parsing and selecting sections of
1555pod documentation from an input stream. This module takes care of
1556identifying pod paragraphs and commands in the input and hands off the
1557parsed paragraphs and commands to user-defined methods which are free
1558to interpret or translate them as they see fit.
d4629d6a
GS
1559
1560Pod::InputObjects defines some input objects needed by Pod::Parser, and
1561for advanced users of Pod::Parser that need more about a command besides
1761cee5 1562its name and text.
d4629d6a
GS
1563
1564As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1565"base parser code" recommended for use by all pod2xxx translators.
1566Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1761cee5
JH
1567to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1568underway. For any questions or comments about pod parsing and translating
1569issues and utilities, please use the pod-people@perl.org mailing list.
d4629d6a 1570
1761cee5 1571For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
d4629d6a 1572
1761cee5 1573=item Pod::Checker, podchecker
d4629d6a 1574
1761cee5
JH
1575This utility checks pod files for correct syntax, according to
1576L<perlpod>. Obvious errors are flagged as such, while warnings are
1577printed for mistakes that can be handled gracefully. The checklist is
1578not complete yet. See L<Pod::Checker>.
d4629d6a 1579
1761cee5 1580=item Pod::ParseUtils, Pod::Find
d4629d6a 1581
1761cee5
JH
1582These modules provide a set of gizmos that are useful mainly for pod
1583translators. L<Pod::Find|Pod::Find> traverses directory structures and
1584returns found pod files, along with their canonical names (like
1585C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1586B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1587(for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1588(for caching information about pod files, e.g. link nodes).
d4629d6a 1589
1761cee5 1590=item Pod::Select, podselect
d4629d6a 1591
1761cee5
JH
1592Pod::Select is a subclass of Pod::Parser which provides a function
1593named "podselect()" to filter out user-specified sections of raw pod
1594documentation from an input stream. podselect is a script that provides
1595access to Pod::Select from other scripts to be used as a filter.
1596See L<Pod::Select>.
d4629d6a 1597
1761cee5 1598=item Pod::Usage, pod2usage
d4629d6a 1599
1761cee5
JH
1600Pod::Usage provides the function "pod2usage()" to print usage messages for
1601a Perl script based on its embedded pod documentation. The pod2usage()
1602function is generally useful to all script authors since it lets them
1603write and maintain a single source (the pods) for documentation, thus
1604removing the need to create and maintain redundant usage message text
1605consisting of information already in the pods.
d4629d6a 1606
1761cee5
JH
1607There is also a pod2usage script which can be used from other kinds of
1608scripts to print usage messages from pods (even for non-Perl scripts
1609with pods embedded in comments).
a5222a85 1610
1761cee5 1611For details and examples, please see L<Pod::Usage>.
a5222a85
GS
1612
1613=item Pod::Text and Pod::Man
1614
1615[TODO - Russ Allbery <rra@stanford.edu>]
1616
f4b9d880
RA
1617=item SDBM_File
1618
1619An EXISTS method has been added to this module (and sdbm_exists() has
1620been added to the underlying sdbm library), so one can now call exists
14218588 1621on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1622runtime error.
1623
a5222a85
GS
1624A bug that may have caused data loss when more than one disk block
1625happens to be read from the database in a single FETCH() has been
1626fixed.
1627
8ce86de8
GS
1628=item Sys::Syslog
1629
1630Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1631no longer requires syslog.ph to exist.
1632
f91101c9
GS
1633=item Sys::Hostname
1634
1635Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1636uname() if they exist.
1637
06ef4121
PC
1638=item Time::Local
1639
1640The timelocal() and timegm() functions used to silently return bogus
437784d6 1641results when the date fell outside the machine's integer range. They
a5222a85 1642now consistently croak() if the date falls in an unsupported range.
06ef4121 1643
8fe0a5c4
JD
1644=item Win32
1645
1646The error return value in list context has been changed for all functions
14218588
GS
1647that return a list of values. Previously these functions returned a list
1648with a single element C<undef> if an error occurred. Now these functions
1649return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1650functions:
1651
14218588
GS
1652 Win32::FsType
1653 Win32::GetOSVersion
8fe0a5c4
JD
1654
1655The remaining functions are unchanged and continue to return C<undef> on
1656error even in list context.
1657
1658The Win32::SetLastError(ERROR) function has been added as a complement
1659to the Win32::GetLastError() function.
1660
1661The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1662pathname for FILENAME in scalar context. In list context it returns
1663a two-element list containing the fully qualified directory name and
501fbaef 1664the filename. See L<Win32>.
8fe0a5c4 1665
9fe6733a
PM
1666=item DBM Filters
1667
1668A new feature called "DBM Filters" has been added to all the
14218588
GS
1669DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1670DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1671
1672 filter_store_key
1673 filter_store_value
1674 filter_fetch_key
1675 filter_fetch_value
1676
14218588 1677These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1678written to the database or just after they are read from the database.
1679See L<perldbmfilter> for further information.
1680
b7d8191e 1681=back
3e8c4fa0
JH
1682
1683=head2 Pragmata
1684
437784d6 1685C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1686backward-compatibility. It's been replaced by the C<sub : attributes>
1687syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1688
14218588 1689C<use utf8> to enable UTF-8 and Unicode support.
43165c05 1690
4438c4b7 1691Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1692See L<perllexwarn>.
6c67e1bb 1693
67d3893f
JH
1694C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1695...). Currently only one subpragma implemented, "use filetest
1696'access';", that uses access(2) or equivalent to check permissions
1697instead of using stat(2) as usual. This matters in filesystems
1698where there are ACLs (access control lists): the stat(2) might lie,
1699but access(2) knows better.
6c67e1bb 1700
ba8251e8
GS
1701=head1 Utility Changes
1702
a5222a85
GS
1703=head2 h2ph
1704
1705[TODO - Kurt Starsinic <kstar@chapin.edu>]
1706
1707=head2 perlcc
1708
1709C<perlcc> now supports the C and Bytecode backends. By default,
1710it generates output from the simple C backend rather than the
1711optimized C backend.
1712
1713Support for non-Unix platforms has been improved.
1714
1715=head2 h2xs
1716
1717change#4232
1718[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
e02fdbd2 1719
ba8251e8
GS
1720=head1 Documentation Changes
1721
5fdc711f
GS
1722=over 4
1723
954c1994
GS
1724=item perlapi.pod
1725
1726The official list of public Perl API functions.
1727
883d36a6
GS
1728=item perlcompile.pod
1729
1730An introduction to using the Perl Compiler suite.
1731
c7c04614
GS
1732=item perlfilter.pod
1733
1734An introduction to writing Perl source filters.
1735
883d36a6
GS
1736=item perlhack.pod
1737
1738Some guidelines for hacking the Perl source code.
1739
954c1994
GS
1740=item perlintern.pod
1741
1742A list of internal functions in the Perl source code.
1743(List is currently empty.)
1744
5fdc711f 1745=item perlopentut.pod
f8284313 1746
5fdc711f
GS
1747A tutorial on using open() effectively.
1748
1749=item perlreftut.pod
1750
1751A tutorial that introduces the essentials of references.
1752
14218588
GS
1753=item perltootc.pod
1754
1755A tutorial on managing class data for object modules.
1756
393fec97
GS
1757=item perlunicode.pod
1758
1759An introduction to Unicode support features in Perl.
1760
5fdc711f 1761=back
e02fdbd2 1762
73b437c8 1763=head1 New or Changed Diagnostics
ba8251e8 1764
a99ba403
GS
1765=over 4
1766
56e90b21
GS
1767=item "%s" variable %s masks earlier declaration in same %s
1768
1769(W) A "my" or "our" variable has been redeclared in the current scope or statement,
1770effectively eliminating all access to the previous instance. This is almost
1771always a typographical error. Note that the earlier variable will still exist
1772until the end of the scope or until all closure referents to it are
1773destroyed.
1774
33633739
GS
1775=item "my sub" not yet implemented
1776
1777(F) Lexically scoped subroutines are not yet implemented. Don't try that
1778yet.
1779
1780=item "our" variable %s redeclared
1781
1782(W) You seem to have already declared the same global once before in the
1783current lexical scope.
1784
a99ba403
GS
1785=item '!' allowed only after types %s
1786
1787(F) The '!' is allowed in pack() and unpack() only after certain types.
1788See L<perlfunc/pack>.
1789
1790=item / cannot take a count
1791
1792(F) You had an unpack template indicating a counted-length string,
1793but you have also specified an explicit size for the string.
1794See L<perlfunc/pack>.
1795
1796=item / must be followed by a, A or Z
1797
1798(F) You had an unpack template indicating a counted-length string,
1799which must be followed by one of the letters a, A or Z
1800to indicate what sort of string is to be unpacked.
1801See L<perlfunc/pack>.
1802
1803=item / must be followed by a*, A* or Z*
1804
437784d6 1805(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1806Currently the only things that can have their length counted are a*, A* or Z*.
1807See L<perlfunc/pack>.
1808
1809=item / must follow a numeric type
1810
1811(F) You had an unpack template that contained a '#',
1812but this did not follow some numeric unpack specification.
1813See L<perlfunc/pack>.
1814
a99ba403
GS
1815=item /%s/: Unrecognized escape \\%c passed through
1816
1817(W) You used a backslash-character combination which is not recognized
1818by Perl. This combination appears in an interpolated variable or a
1028017a
JH
1819C<'>-delimited regular expression. The character was understood literally.
1820
1821=item /%s/: Unrecognized escape \\%c in character class passed through
1822
1823(W) You used a backslash-character combination which is not recognized
1824by Perl inside character classes. The character was understood literally.
a99ba403
GS
1825
1826=item /%s/ should probably be written as "%s"
1827
1828(W) You have used a pattern where Perl expected to find a string,
437784d6 1829as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
1830or false result of matching the pattern against $_ as the string,
1831which is probably not what you had in mind.
1832
1833=item %s() called too early to check prototype
1834
1835(W) You've called a function that has a prototype before the parser saw a
1836definition or declaration for it, and Perl could not check that the call
1837conforms to the prototype. You need to either add an early prototype
1838declaration for the subroutine in question, or move the subroutine
1839definition ahead of the call to get proper prototype checking. Alternatively,
1840if you are certain that you're calling the function correctly, you may put
1841an ampersand before the name to avoid the warning. See L<perlsub>.
1842
56e90b21
GS
1843=item %s argument is not a HASH or ARRAY element
1844
1845(F) The argument to exists() must be a hash or array element, such as:
1846
1847 $foo{$bar}
1848 $ref->[12]->["susie"]
1849
1850=item %s argument is not a HASH or ARRAY element or slice
1851
1852(F) The argument to delete() must be either a hash or array element, such as:
1853
1854 $foo{$bar}
1855 $ref->[12]->["susie"]
1856
1857or a hash or array slice, such as:
1858
1859 @foo[$bar, $baz, $xyzzy]
1860 @{$ref->[12]}{"susie", "queue"}
1861
afebc493
GS
1862=item %s argument is not a subroutine name
1863
1864(F) The argument to exists() for C<exists &sub> must be a subroutine
1865name, and not a subroutine call. C<exists &sub()> will generate this error.
1866
09bef843
SB
1867=item %s package attribute may clash with future reserved word: %s
1868
1869(W) A lowercase attribute name was used that had a package-specific handler.
1870That name might have a meaning to Perl itself some day, even though it
1871doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1872See L<attributes>.
1873
a99ba403 1874=item (in cleanup) %s
6b121555 1875
a99ba403
GS
1876(W) This prefix usually indicates that a DESTROY() method raised
1877the indicated exception. Since destructors are usually called by
1878the system at arbitrary points during execution, and often a vast
1879number of times, the warning is issued only once for any number
1880of failures that would otherwise result in the same message being
1881repeated.
1882
1883Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1884could also result in this warning. See L<perlcall/G_KEEPERR>.
1885
1886=item <> should be quotes
1887
1888(F) You wrote C<require E<lt>fileE<gt>> when you should have written
1889C<require 'file'>.
1890
1891=item Attempt to join self
1892
1893(F) You tried to join a thread from within itself, which is an
1894impossible task. You may be joining the wrong thread, or you may
1895need to move the join() to some other thread.
1896
1897=item Bad evalled substitution pattern
1898
1899(F) You've used the /e switch to evaluate the replacement for a
1900substitution, but perl found a syntax error in the code to evaluate,
1901most likely an unexpected right brace '}'.
1902
1903=item Bad realloc() ignored
1904
1905(S) An internal routine called realloc() on something that had never been
1906malloc()ed in the first place. Mandatory, but can be disabled by
1907setting environment variable C<PERL_BADFREE> to 1.
1908
1909=item Binary number > 0b11111111111111111111111111111111 non-portable
1910
1911(W) The binary number you specified is larger than 2**32-1
1912(4294967295) and therefore non-portable between systems. See
1913L<perlport> for more on portability concerns.
1914
1915=item Bit vector size > 32 non-portable
1916
1917(W) Using bit vector sizes larger than 32 is non-portable.
1918
1919=item Buffer overflow in prime_env_iter: %s
1920
1921(W) A warning peculiar to VMS. While Perl was preparing to iterate over
1922%ENV, it encountered a logical name or symbol definition which was too long,
1923so it was truncated to the string shown.
1924
1925=item Can't check filesystem of script "%s"
1926
1927(P) For some reason you can't check the filesystem of the script for nosuid.
1928
56e90b21
GS
1929=item Can't declare class for non-scalar %s in "%s"
1930
1931(S) Currently, only scalar variables can declared with a specific class
1932qualifier in a "my" or "our" declaration. The semantics may be extended
1933for other types of variables in future.
1934
1935=item Can't declare %s in "%s"
1936
1937(F) Only scalar, array, and hash variables may be declared as "my" or
1938"our" variables. They must have ordinary identifiers as names.
1939
0b5b802d
GS
1940=item Can't ignore signal CHLD, forcing to default
1941
1942(W) Perl has detected that it is being run with the SIGCHLD signal
1943(sometimes known as SIGCLD) disabled. Since disabling this signal
1944will interfere with proper determination of exit status of child
1945processes, Perl has reset the signal to its default value.
1946This situation typically indicates that the parent program under
1947which Perl may be running (e.g. cron) is being very careless.
1948
a99ba403
GS
1949=item Can't modify non-lvalue subroutine call
1950
437784d6
GS
1951(F) Subroutines meant to be used in lvalue context should be declared as
1952such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
1953
1954=item Can't read CRTL environ
1955
1956(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1957from the CRTL's internal environment array and discovered the array was
1958missing. You need to figure out where your CRTL misplaced its environ
1959or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1960
1961=item Can't remove %s: %s, skipping file
1962
1963(S) You requested an inplace edit without creating a backup file. Perl
1964was unable to remove the original file to replace it with the modified
1965file. The file was left unmodified.
1966
1967=item Can't return %s from lvalue subroutine
1968
1969(F) Perl detected an attempt to return illegal lvalues (such
1970as temporary or readonly values) from a subroutine used as an lvalue.
1971This is not allowed.
1972
1973=item Can't weaken a nonreference
1974
1975(F) You attempted to weaken something that was not a reference. Only
1976references can be weakened.
1977
1978=item Character class [:%s:] unknown
1979
1980(F) The class in the character class [: :] syntax is unknown.
437784d6 1981See L<perlre>.
a99ba403
GS
1982
1983=item Character class syntax [%s] belongs inside character classes
1984
1985(W) The character class constructs [: :], [= =], and [. .] go
1986I<inside> character classes, the [] are part of the construct,
437784d6
GS
1987for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1988are not currently implemented; they are simply placeholders for
1989future extensions.
a99ba403
GS
1990
1991=item Constant is not %s reference
1992
1993(F) A constant value (perhaps declared using the C<use constant> pragma)
1994is being dereferenced, but it amounts to the wrong type of reference. The
1995message indicates the type of reference that was expected. This usually
1996indicates a syntax error in dereferencing the constant value.
1997See L<perlsub/"Constant Functions"> and L<constant>.
1998
1999=item constant(%s): %%^H is not localized
2000
2001(F) When setting compile-time-lexicalized hash %^H one should set the
2002corresponding bit of $^H as well.
2003
2004=item constant(%s): %s
2005
2006(F) Compile-time-substitutions (such as overloaded constants and
2007character names) were not correctly set up.
2008
2009=item defined(@array) is deprecated
2010
2011(D) defined() is not usually useful on arrays because it checks for an
2012undefined I<scalar> value. If you want to see if the array is empty,
2013just use C<if (@array) { # not empty }> for example.
2014
2015=item defined(%hash) is deprecated
2016
2017(D) defined() is not usually useful on hashes because it checks for an
2018undefined I<scalar> value. If you want to see if the hash is empty,
2019just use C<if (%hash) { # not empty }> for example.
2020
2021=item Did not produce a valid header
2022
2023See Server error.
2024
33633739
GS
2025=item Did you mean "local" instead of "our"?
2026
2027(W) Remember that "our" does not localize the declared global variable.
2028You have declared it again in the same lexical scope, which seems superfluous.
2029
a99ba403
GS
2030=item Document contains no data
2031
2032See Server error.
2033
2034=item entering effective %s failed
2035
2036(F) While under the C<use filetest> pragma, switching the real and
2037effective uids or gids failed.
6b121555 2038
73b437c8
JH
2039=item false [] range "%s" in regexp
2040
2041(W) A character class range must start and end at a literal character, not
2042another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2043range is interpreted as a literal "-". Consider quoting the "-", "\-".
2044See L<perlre>.
2045
af8c498a 2046=item Filehandle %s opened only for output
6b121555 2047
af8c498a 2048(W) You tried to read from a filehandle opened only for writing. If you
437784d6 2049intended it to be a read/write filehandle, you needed to open it with
af8c498a
GS
2050"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2051you intended only to read from the file, use "E<lt>". See
2052L<perlfunc/open>.
e02fdbd2 2053
56e90b21
GS
2054=item flock() on closed filehandle %s
2055
2056(W) The filehandle you're attempting to flock() got itself closed some
2057time before now. Check your logic flow. flock() operates on filehandles.
2058Are you attempting to call flock() on a dirhandle by the same name?
2059
2060=item Global symbol "%s" requires explicit package name
2061
2062(F) You've said "use strict vars", which indicates that all variables
2063must either be lexically scoped (using "my"), declared beforehand using
2064"our", or explicitly qualified to say which package the global variable
2065is in (using "::").
2066
a99ba403
GS
2067=item Hexadecimal number > 0xffffffff non-portable
2068
2069(W) The hexadecimal number you specified is larger than 2**32-1
2070(4294967295) and therefore non-portable between systems. See
2071L<perlport> for more on portability concerns.
2072
2073=item Ill-formed CRTL environ value "%s"
2074
2075(W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2076environ array, and encountered an element without the C<=> delimiter
2077used to spearate keys from values. The element is ignored.
2078
2079=item Ill-formed message in prime_env_iter: |%s|
2080
2081(W) A warning peculiar to VMS. Perl tried to read a logical name
2082or CLI symbol definition when preparing to iterate over %ENV, and
2083didn't see the expected delimiter between key and value, so the
2084line was ignored.
2085
2086=item Illegal binary digit %s
2087
437784d6 2088(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
2089
2090=item Illegal binary digit %s ignored
2091
2092(W) You may have tried to use a digit other than 0 or 1 in a binary number.
2093Interpretation of the binary number stopped before the offending digit.
2094
2095=item Illegal number of bits in vec
2096
2097(F) The number of bits in vec() (the third argument) must be a power of
2098two from 1 to 32 (or 64, if your platform supports that).
2099
2100=item Integer overflow in %s number
2101
2102(W) The hexadecimal, octal or binary number you have specified either
c6edd1b7 2103as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
2104architecture, and has been converted to a floating point number. On a
210532-bit architecture the largest hexadecimal, octal or binary number
2106representable without overflow is 0xFFFFFFFF, 037777777777, or
21070b11111111111111111111111111111111 respectively. Note that Perl
2108transparently promotes all numbers to a floating point representation
2109internally--subject to loss of precision errors in subsequent
2110operations.
2111
09bef843
SB
2112=item Invalid %s attribute: %s
2113
2114The indicated attribute for a subroutine or variable was not recognized
2115by Perl or by a user-supplied handler. See L<attributes>.
2116
2117=item Invalid %s attributes: %s
2118
2119The indicated attributes for a subroutine or variable were not recognized
2120by Perl or by a user-supplied handler. See L<attributes>.
2121
73b437c8
JH
2122=item invalid [] range "%s" in regexp
2123
2124The offending range is now explicitly displayed.
2125
09bef843
SB
2126=item Invalid separator character %s in attribute list
2127
0120eecf 2128(F) Something other than a colon or whitespace was seen between the
09bef843
SB
2129elements of an attribute list. If the previous attribute
2130had a parenthesised parameter list, perhaps that list was terminated
2131too soon. See L<attributes>.
2132
a99ba403
GS
2133=item Invalid separator character %s in subroutine attribute list
2134
0120eecf 2135(F) Something other than a colon or whitespace was seen between the
a99ba403
GS
2136elements of a subroutine attribute list. If the previous attribute
2137had a parenthesised parameter list, perhaps that list was terminated
2138too soon.
2139
2140=item leaving effective %s failed
2141
2142(F) While under the C<use filetest> pragma, switching the real and
2143effective uids or gids failed.
2144
2145=item Lvalue subs returning %s not implemented yet
2146
2147(F) Due to limitations in the current implementation, array and hash
2148values cannot be returned in subroutines used in lvalue context.
2149See L<perlsub/"Lvalue subroutines">.
2150
2151=item Method %s not permitted
2152
2153See Server error.
2154
2155=item Missing %sbrace%s on \N{}
2156
2157(F) Wrong syntax of character name literal C<\N{charname}> within
2158double-quotish context.
2159
06eaf0bc
GS
2160=item Missing command in piped open
2161
2162(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2163construction, but the command was missing or blank.
2164
09bef843
SB
2165=item Missing name in "my sub"
2166
2167(F) The reserved syntax for lexically scoped subroutines requires that they
2168have a name with which they can be found.
2169
56e90b21
GS
2170=item No %s specified for -%c
2171
2172(F) The indicated command line switch needs a mandatory argument, but
2173you haven't specified one.
2174
2175=item No package name allowed for variable %s in "our"
2176
2177(F) Fully qualified variable names are not allowed in "our" declarations,
2178because that doesn't make much sense under existing semantics. Such
2179syntax is reserved for future extensions.
2180
2181=item No space allowed after -%c
2182
2183(F) The argument to the indicated command line switch must follow immediately
2184after the switch, without intervening spaces.
2185
a99ba403
GS
2186=item no UTC offset information; assuming local time is UTC
2187
2188(S) A warning peculiar to VMS. Perl was unable to find the local
2189timezone offset, so it's assuming that local system time is equivalent
2190to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2191to translate to the number of seconds which need to be added to UTC to
2192get local time.
2193
2194=item Octal number > 037777777777 non-portable
2195
2196(W) The octal number you specified is larger than 2**32-1 (4294967295)
2197and therefore non-portable between systems. See L<perlport> for more
2198on portability concerns.
2199
2200See also L<perlport> for writing portable code.
2201
2202=item panic: del_backref
2203
2204(P) Failed an internal consistency check while trying to reset a weak
2205reference.
2206
2207=item panic: kid popen errno read
2208
2209(F) forked child returned an incomprehensible message about its errno.
2210
2211=item panic: magic_killbackrefs
2212
2213(P) Failed an internal consistency check while trying to reset all weak
2214references to an object.
2215
56e90b21
GS
2216=item Parentheses missing around "%s" list
2217
2218(W) You said something like
2219
2220 my $foo, $bar = @_;
2221
2222when you meant
2223
2224 my ($foo, $bar) = @_;
2225
2226Remember that "my", "our" and "local" bind closer than comma.
2227
a99ba403
GS
2228=item Possible Y2K bug: %s
2229
2230(W) You are concatenating the number 19 with another number, which
2231could be a potential Year 2000 problem.
2232
2233=item Premature end of script headers
2234
2235See Server error.
2236
0b5b802d
GS
2237=item Repeat count in pack overflows
2238
2239(F) You can't specify a repeat count so large that it overflows
2240your signed integers. See L<perlfunc/pack>.
2241
2242=item Repeat count in unpack overflows
2243
2244(F) You can't specify a repeat count so large that it overflows
2245your signed integers. See L<perlfunc/unpack>.
2246
a99ba403
GS
2247=item realloc() of freed memory ignored
2248
2249(S) An internal routine called realloc() on something that had already
2250been freed.
2251
2252=item Reference is already weak
2253
2254(W) You have attempted to weaken a reference that is already weak.
2255Doing so has no effect.
2256
2257=item setpgrp can't take arguments
2258
2259(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2260unlike POSIX setpgid(), which takes a process ID and process group ID.
2261
2262=item Strange *+?{} on zero-length expression
2263
2264(W) You applied a regular expression quantifier in a place where it
2265makes no sense, such as on a zero-width assertion.
2266Try putting the quantifier inside the assertion instead. For example,
2267the way to match "abc" provided that it is followed by three
2268repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2269
2270=item switching effective %s is not implemented
2271
2272(F) While under the C<use filetest> pragma, we cannot switch the
2273real and effective uids or gids.
2274
437784d6 2275=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
2276
2277=item This Perl can't set CRTL environ elements (%s=%s)
2278
2279(W) Warnings peculiar to VMS. You tried to change or delete an element
2280of the CRTL's internal environ array, but your copy of Perl wasn't
2281built with a CRTL that contained the setenv() function. You'll need to
2282rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2283L<perlvms>) so that the environ array isn't the target of the change to
2284%ENV which produced the warning.
2285
2286=item Unknown open() mode '%s'
2287
437784d6 2288(F) The second argument of 3-argument open() is not among the list
1761cee5
JH
2289of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2290C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
a99ba403
GS
2291
2292=item Unknown process %x sent message to prime_env_iter: %s
2293
2294(P) An error peculiar to VMS. Perl was reading values for %ENV before
2295iterating over it, and someone else stuck a message in the stream of
2296data Perl expected. Someone's very confused, or perhaps trying to
2297subvert Perl's population of %ENV for nefarious purposes.
2298
af8c498a
GS
2299=item Unrecognized escape \\%c passed through
2300
2301(W) You used a backslash-character combination which is not recognized
1028017a 2302by Perl. The character was understood literally.
af8c498a 2303
09bef843
SB
2304=item Unterminated attribute parameter in attribute list
2305
2306(F) The lexer saw an opening (left) parenthesis character while parsing an
2307attribute list, but the matching closing (right) parenthesis
2308character was not found. You may need to add (or remove) a backslash
2309character to get your parentheses to balance. See L<attributes>.
2310
2311=item Unterminated attribute list
2312
2313(F) The lexer found something other than a simple identifier at the start
2314of an attribute, and it wasn't a semicolon or the start of a
2315block. Perhaps you terminated the parameter list of the previous attribute
2316too soon. See L<attributes>.
2317
09bef843
SB
2318=item Unterminated attribute parameter in subroutine attribute list
2319
2320(F) The lexer saw an opening (left) parenthesis character while parsing a
2321subroutine attribute list, but the matching closing (right) parenthesis
2322character was not found. You may need to add (or remove) a backslash
2323character to get your parentheses to balance.
2324
2325=item Unterminated subroutine attribute list
2326
2327(F) The lexer found something other than a simple identifier at the start
2328of a subroutine attribute, and it wasn't a semicolon or the start of a
2329block. Perhaps you terminated the parameter list of the previous attribute
2330too soon.
2331
a99ba403 2332=item Value of CLI symbol "%s" too long
eb6e2d6f 2333
a99ba403
GS
2334(W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2335element from a CLI symbol table, and found a resultant string longer
2336than 1024 characters. The return value has been truncated to 1024
2337characters.
eb6e2d6f 2338
a99ba403 2339=item Version number must be a constant number
ba8251e8 2340
a99ba403
GS
2341(P) The attempt to translate a C<use Module n.n LIST> statement into
2342its equivalent C<BEGIN> block found an internal inconsistency with
2343the version number.
2344
2345=back
27806c82 2346
a5222a85 2347=head1 Obsolete Diagnostics
3175b8cd 2348
a99ba403
GS
2349=over 4
2350
2351=item Character class syntax [: :] is reserved for future extensions
2352
2353(W) Within regular expression character classes ([]) the syntax beginning
2354with "[:" and ending with ":]" is reserved for future extensions.
2355If you need to represent those character sequences inside a regular
2356expression character class, just quote the square brackets with the
2357backslash: "\[:" and ":\]".
2358
2359=item Ill-formed logical name |%s| in prime_env_iter
2360
2361(W) A warning peculiar to VMS. A logical name was encountered when preparing
2362to iterate over %ENV which violates the syntactic rules governing logical
2363names. Because it cannot be translated normally, it is skipped, and will not
2364appear in %ENV. This may be a benign occurrence, as some software packages
2365might directly modify logical name tables and introduce nonstandard names,
2366or it may indicate that a logical name table has been corrupted.
2367
2368=item regexp too big
2369
2370(F) The current implementation of regular expressions uses shorts as
2371address offsets within a string. Unfortunately this means that if
2372the regular expression compiles to longer than 32767, it'll blow up.
2373Usually when you want a regular expression this big, there is a better
2374way to do it with multiple statements. See L<perlre>.
2375
2376=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2377
2378(D) Perl versions before 5.004 misinterpreted any type marker followed
2379by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2380"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2381
2382However, the developers of Perl 5.004 could not fix this bug completely,
2383because at least two widely-used modules depend on the old meaning of
2384"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2385old (broken) way inside strings; but it generates this message as a
2386warning. And in Perl 5.005, this special treatment will cease.
2387
2388=back
3175b8cd 2389
ba8251e8
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2390=head1 BUGS
2391
437784d6 2392If you find what you think is a bug, you might check the
14218588 2393articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
GS
2394There may also be information at http://www.perl.com/perl/, the Perl
2395Home Page.
2396
2397If you believe you have an unreported bug, please run the B<perlbug>
14218588 2398program included with your release. Make sure to trim your bug down
ba8251e8 2399to a tiny but sufficient test case. Your bug report, along with the
14218588 2400output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
GS
2401analysed by the Perl porting team.
2402
2403=head1 SEE ALSO
2404
2405The F<Changes> file for exhaustive details on what changed.
2406
2407The F<INSTALL> file for how to build Perl.
2408
2409The F<README> file for general stuff.
2410
2411The F<Artistic> and F<Copying> files for copyright information.
2412
2413=head1 HISTORY
2414
a5222a85
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2415Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2416contributions from The Perl Porters.
ba8251e8
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2417
2418Send omissions or corrections to <F<perlbug@perl.com>>.
2419
2420=cut