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1=head1 NAME
2
063663a9 3perldelta - what's new for perl v5.6.0
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4
5=head1 DESCRIPTION
6
7This document describes differences between the 5.005 release and this one.
8
9=head1 Incompatible Changes
10
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11=head2 Perl Source Incompatibilities
12
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13Beware that any new warnings that have been added or old ones
14that have been enhanced are B<not> considered incompatible changes.
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15
16Since all new warnings must be explicitly requested via the C<-w>
17switch or the C<warnings> pragma, it is ultimately the programmer's
18responsibility to ensure that warnings are enabled judiciously.
e02fdbd2 19
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20=over 4
21
7d30b5c4 22=item CHECK is a new keyword
4f25aa18 23
40b7eeef 24In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
7d30b5c4 25subroutines named C<CHECK> are now special. These are queued up during
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26compilation and behave similar to END blocks, except they are called at
27the end of compilation rather than at the end of execution. They cannot
28be called directly.
4f25aa18 29
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30=item Treatment of list slices of undef has changed
31
32When taking a slice of a literal list (as opposed to a slice of
33an array or hash), Perl used to return an empty list if the
34result happened to be composed of all undef values.
35
36The new behavior is to produce an empty list if (and only if)
37the original list was empty. Consider the following example:
38
39 @a = (1,undef,undef,2)[2,1,2];
40
41The old behavior would have resulted in @a having no elements.
42The new behavior ensures it has three undefined elements.
43
44Note in particular that the behavior of slices of the following
45cases remains unchanged:
46
47 @a = ()[1,2];
48 @a = (getpwent)[7,0];
49 @a = (anything_returning_empty_list())[2,1,2];
50 @a = @b[2,1,2];
51 @a = @c{'a','b','c'};
52
53See L<perldata>.
54
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55=head2 Perl's version numbering has changed
56
063663a9 57Beginning with Perl version 5.6.0, the version number convention has been
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58changed to a "dotted integer" scheme that is more commonly found in open
59source projects.
60
61Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
063663a9 62The next development series following v5.6.0 will be numbered v5.7.x,
44dcb63b 63beginning with v5.7.0, and the next major production release following
063663a9 64v5.6.0 will be v5.8.0.
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65
66The English module now sets $PERL_VERSION to $^V (a string value) rather
67than C<$]> (a numeric value). (This is a potential incompatibility.
68Send us a report via perlbug if you are affected by this.)
69
70The v1.2.3 syntax is also now legal in Perl.
71See L<Support for strings represented as a vector of ordinals> for more on that.
72
73To cope with the new versioning system's use of at least three significant
74digits for each version component, the method used for incrementing the
75subversion number has also changed slightly. We assume that versions older
063663a9 76than v5.6.0 have been incrementing the subversion component in multiples of
44dcb63b 7710. Versions after v5.6.0 will increment them by 1. Thus, using the new
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78notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
79version following v5.6.0 will be v5.6.1 (which should be read as being
80equivalent to a floating point value of 5.006_001 in the older format,
81stored in C<$]>).
44dcb63b 82
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83=item Literals of the form C<1.2.3> parse differently
84
85Previously, numeric literals with more than one dot in them were
86interpreted as a floating point number concatenated with one or more
87numbers. Such "numbers" are now parsed as strings composed of the
88specified ordinals.
89
90For example, C<print 97.98.99> used to output C<97.9899> in earlier
91versions, but now prints C<abc>.
92
93See L<Support for strings represented as a vector of ordinals> below.
94
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95=item Possibly changed pseudo-random number generator
96
97In 5.005_0x and earlier, perl's rand() function used the C library
98rand(3) function. As of 5.005_52, Configure tests for drand48(),
99random(), and rand() (in that order) and picks the first one it finds.
100Perl programs that depend on reproducing a specific set of pseudo-random
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101numbers will now likely produce different output. You can use
102C<sh Configure -Drandfunc=rand> to obtain the old behavior.
757edf6f 103
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104=item Hashing function for hash keys has changed
105
106Perl hashes are not order preserving. The apparently random order
107encountered when iterating on the contents of a hash is determined
108by the hashing algorithm used. To improve the distribution of lower
109bits in the hashed value, the algorithm has changed slightly as of
1105.005_52. When iterating over hashes, this may yield a random order
111that is B<different> from that of previous versions.
112
113=item C<undef> fails on read only values
114
115Using the C<undef> operator on a readonly value (such as $1) has
116the same effect as assigning C<undef> to the readonly value--it
117throws an exception.
118
8d2a6795 119=item Close-on-exec bit may be set on pipe and socket handles
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120
121On systems that support a close-on-exec flag on filehandles, the
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122flag will be set for any handles created by pipe(), socketpair(),
123socket(), and accept(), if that is warranted by the value of $^F
124that may be in effect. Earlier versions neglected to set the flag
125for handles created with these operators. See L<perlfunc/pipe>,
126L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
127and L<perlvar/$^F>.
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128
129=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
130
131Perl 5.004 deprecated the interpretation of C<$$1> and
132similar within interpolated strings to mean C<$$ . "1">,
133but still allowed it.
134
135In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
136
94f7643d 137=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
a5222a85 138
94f7643d 139delete(), each(), values() and hashes in a list context return the actual
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140values in the hash, instead of copies (as they used to in earlier
141versions). Typical idioms for using these constructs copy the
501fbaef 142returned values, but this can make a significant difference when
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143creating references to the returned values.
144
145Keys in the hash are still returned as copies when iterating on
08cd8952 146a hash.
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147
148=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
149
08cd8952 150vec() generates a run-time error if the BITS argument is not
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151a valid power-of-two integer.
152
153=item Text of some diagnostic output has changed
154
155Most references to internal Perl operations in diagnostics
156have been changed to be more descriptive. This may be an
157issue for programs that may incorrectly rely on the exact
158text of diagnostics for proper functioning.
159
160=item C<%@> has been removed
161
162The undocumented special variable C<%@> that used to accumulate
163"background" errors (such as those that happen in DESTROY())
164has been removed, because it could potentially result in memory
165leaks.
166
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167=item Parenthesized not() behaves like a list operator
168
169The C<not> operator now falls under the "if it looks like a function,
170it behaves like a function" rule.
171
172As a result, the parenthesized form can be used with C<grep> and C<map>.
173The following construct used to be a syntax error before, but it works
174as expected now:
175
176 grep not($_), @things;
177
178On the other hand, using C<not> with a literal list slice may not
179work. The following previously allowed construct:
180
181 print not (1,2,3)[0];
182
af365420 183needs to be written with additional parentheses now:
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184
185 print not((1,2,3)[0]);
186
187The behavior remains unaffected when C<not> is not followed by parentheses.
188
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189=item Semantics of bareword prototype C<(*)> have changed
190
191Arguments prototyped as C<*> will now be visible within the subroutine
192as either a simple scalar or as a reference to a typeglob. Perl 5.005
193always coerced simple scalar arguments to a typeglob, which wasn't useful
194in situations where the subroutine must distinguish between a simple
195scalar and a typeglob. See L<perlsub/Prototypes>.
196
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197=head2 On 64-bit platforms the semantics of bit operators have changed
198
199If your platform is either natively 64-bit or your Perl has been
200configured to used 64-bit integers (say C<perl -V> and see what is
201your ivsize: if it is 8, you are 64-bit) , be warned that the
202semantics of all the bitwise numeric operators (& | ^ ~ << >>) have
203been changed. They used to be forced to be 32 bits wide, but now in
204the aforementioned platforms they are 64 bits wide. Most dramatically
205this affects the unary ~: what used to be 32 bits wide, is now 64 bits
206wide. If you depend on your integers being 32 bits wide, mask off the
207excess bits with C<& 0xffffffff>.
208
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209=back
210
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211=head2 C Source Incompatibilities
212
213=over 4
214
215=item C<PERL_POLLUTE>
216
217Release 5.005 grandfathered old global symbol names by providing preprocessor
87275199 218macros for extension source compatibility. As of release 5.6, these
e02fdbd2 219preprocessor definitions are not available by default. You need to explicitly
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220compile perl with C<-DPERL_POLLUTE> to get these definitions. For
221extensions still using the old symbols, this option can be
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222specified via MakeMaker:
223
14218588 224 perl Makefile.PL POLLUTE=1
e02fdbd2 225
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226=item C<PERL_IMPLICIT_CONTEXT>
227
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228PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
229with one of -Dusethreads, -Dusemultiplicity, or both. It is not
230intended to be enabled by users at this time.
231
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232This new build option provides a set of macros for all API functions
233such that an implicit interpreter/thread context argument is passed to
234every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 235amounts to a macro invocation that actually translates to something like
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236C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
237to not have any significant source compatibility issues, the difference
238between a macro and a real function call will need to be considered.
239
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240This means that there B<is> a source compatibility issue as a result of
241this if your extensions attempt to use pointers to any of the Perl API
242functions.
243
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244Note that the above issue is not relevant to the default build of
245Perl, whose interfaces continue to match those of prior versions
246(but subject to the other options described here).
247
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248See L<perlguts/"The Perl API"> for detailed information on the
249ramifications of building Perl using this option.
250
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251=item C<PERL_POLLUTE_MALLOC>
252
14218588 253Enabling Perl's malloc in release 5.005 and earlier caused
86058a2d 254the namespace of system versions of the malloc family of functions to
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255be usurped by the Perl versions, since by default they used the
256same names.
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257
258Besides causing problems on platforms that do not allow these functions to
259be cleanly replaced, this also meant that the system versions could not
260be called in programs that used Perl's malloc. Previous versions of Perl
14218588 261have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
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262EMBEDMYMALLOC preprocessor definitions.
263
87275199 264As of release 5.6, Perl's malloc family of functions have default names
86058a2d 265distinct from the system versions. You need to explicitly compile perl with
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266C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
267and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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268the default.
269
270Note that these functions do B<not> constitute Perl's memory allocation API.
271See L<perlguts/"Memory Allocation"> for further information about that.
272
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273=back
274
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275=head2 Compatible C Source API Changes
276
277=over
278
279=item C<PATCHLEVEL> is now C<PERL_VERSION>
280
14218588 281The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 282are now available by default from perl.h, and reflect the base revision,
14218588 283patchlevel, and subversion respectively. C<PERL_REVISION> had no
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284prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
285previously available as C<PATCHLEVEL> and C<SUBVERSION>.
286
14218588 287The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 288the numbers have come to stand for in common practice. For compatibility,
14218588 289the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 290included (as required before), so there is no source incompatibility
14218588 291from the change.
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292
293=back
294
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295=head2 Binary Incompatibilities
296
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297In general, the default build of this release is expected to be binary
298compatible for extensions built with the 5.005 release or its maintenance
299versions. However, specific platforms may have broken binary compatibility
300due to changes in the defaults used in hints files. Therefore, please be
301sure to always check the platform-specific README files for any notes to
302the contrary.
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303
304The usethreads or usemultiplicity builds are B<not> binary compatible
305with the corresponding builds in 5.005.
e02fdbd2 306
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307On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
308among others), purely internal symbols such as parser functions and the
309run time opcodes are not exported by default. Perl 5.005 used to export
310all functions irrespective of whether they were considered part of the
311public API or not.
312
313For the full list of public API functions, see L<perlapi>.
314
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315=head1 Installation and Configuration Improvements
316
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317=head2 -Dusethreads means something different
318
319WARNING: Support for threads continues to be an experimental feature.
320Interfaces and implementation are subject to sudden and drastic changes.
321
322The -Dusethreads flag now enables the experimental interpreter-based thread
323support by default. To get the flavor of experimental threads that was in
ba869deb 3245.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
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325
326As of v5.5.640, interpreter-threads support is still lacking a way to
327create new threads from Perl (i.e., C<use Thread;> will not work with
328interpreter threads). C<use Thread;> continues to be available when you
ba869deb 329ask for use5005threads, bugs and all.
16070b82 330
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331=head2 New Configure flags
332
333The following new flags may be enabled on the Configure command line
334by running Configure with C<-Dflag>.
335
336 usemultiplicity
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337 usethreads useithreads (new interpreter threads: no Perl API yet)
338 usethreads use5005threads (threads as they were in 5.005)
67d3893f 339
ba869deb 340 use64bitint (equal to now deprecated 'use64bits')
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341 use64bitall
342
67d3893f 343 uselongdouble
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344 usemorebits
345 uselargefiles
ba869deb 346 usesocks (only SOCKS v5 supported)
a5222a85 347
10cc9d2a 348=head2 Threadedness and 64-bitness now more daring
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349
350The Configure options enabling the use of threads and the use of
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35164-bitness are now more daring in the sense that they no more have an
352explicit list of operating systems of known threads/64-bit
67d3893f 353capabilities. In other words: if your operating system has the
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354necessary APIs and datatypes, you should be able just to go ahead and
355use them, for threads by Configure -Dusethreads, and for 64 bits
10cc9d2a 356either explicitly by Configure -Duse64bitint or implicitly if your
132ca540 357system has 64 bit wide datatypes. See also L<"64-bit support">.
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358
359=head2 Long Doubles
360
361Some platforms have "long doubles", floating point numbers of even
437784d6 362larger range than ordinary "doubles". To enable using long doubles for
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363Perl's scalars, use -Duselongdouble.
364
365=head2 -Dusemorebits
366
10cc9d2a 367You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
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368See also L<"64-bit support">.
369
370=head2 -Duselargefiles
371
372Some platforms support large files, files larger than two gigabytes.
373See L<"Large file support"> for more information.
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374
375=head2 installusrbinperl
376
377You can use "Configure -Uinstallusrbinperl" which causes installperl
378to skip installing perl also as /usr/bin/perl. This is useful if you
379prefer not to modify /usr/bin for some reason or another but harmful
380because many scripts assume to find Perl in /usr/bin/perl.
381
382=head2 SOCKS support
383
384You can use "Configure -Dusesocks" which causes Perl to probe
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385for the SOCKS (v5, not v4) proxy protocol library,
386http://www.socks.nec.com/
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387
388=head2 C<-A> flag
389
390You can "post-edit" the Configure variables using the Configure C<-A>
391flag. The editing happens immediately after the platform specific
392hints files have been processed but before the actual configuration
393process starts. Run C<Configure -h> to find out the full C<-A> syntax.
394
c35dd67d 395=head2 Enhanced Installation Directories
67d3893f 396
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397The installation structure has been enriched to improve the support
398for maintaining multiple versions of perl, to provide locations for
399vendor-supplied modules, scripts, and manpages, and to ease maintenance
400of locally-added modules, scripts, and manpages. See the section on
401Installation Directories in the INSTALL file for complete details.
402For most users building and installing from source, the defaults should
403be fine.
404
405If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
406special values for library directories, you might wish to consider using
407the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
408config.sh file from an earlier version of perl, you should be sure to
409check that Configure makes sensible choices for the new directories.
410See INSTALL for complete details.
67d3893f 411
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412=head1 Core Changes
413
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414=head2 Unicode and UTF-8 support
415
416Perl can optionally use UTF-8 as its internal representation for character
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417strings. The C<utf8> and C<bytes> pragmas are used to control this support
418in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
393fec97 419more information.
9d73390d 420
16070b82 421=head2 Interpreter cloning, threads, and concurrency
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422
423WARNING: This is an experimental feature in a pre-alpha state. Use
424at your own risk.
425
426Perl 5.005_63 introduces the beginnings of support for running multiple
427interpreters concurrently in different threads. In conjunction with
428the perl_clone() API call, which can be used to selectively duplicate
429the state of any given interpreter, it is possible to compile a
430piece of code once in an interpreter, clone that interpreter
431one or more times, and run all the resulting interpreters in distinct
432threads.
433
434On Windows, this feature is used to emulate fork() at the interpreter
435level. See L<perlfork>.
436
437This feature is still in evolution. It is eventually meant to be used
438to selectively clone a subroutine and data reachable from that
439subroutine in a separate interpreter and run the cloned subroutine
440in a separate thread. Since there is no shared data between the
441interpreters, little or no locking will be needed (unless parts of
442the symbol table are explicitly shared). This is obviously intended
443to be an easy-to-use replacement for the existing threads support.
444
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445Support for cloning interpreters and interpreter concurrency can be
446enabled using the -Dusethreads Configure option (see win32/Makefile for
447how to enable it on Windows.) The resulting perl executable will be
448functionally identical to one that was built with -Dmultiplicity, but
449the perl_clone() API call will only be available in the former.
af365420 450
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451-Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
452Perl source code changes that provide a clear separation between the op tree
453and the data it operates with. The former is considered immutable, and can
454therefore be shared between an interpreter and all of its clones, while the
455latter is considered local to each interpreter, and is therefore copied for
456each clone.
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457
458Note that building Perl with the -Dusemultiplicity Configure option
459is adequate if you wish to run multiple B<independent> interpreters
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460concurrently in different threads. -Dusethreads only provides the
461additional functionality of the perl_clone() API call and other
462support for running B<cloned> interpreters concurrently.
af365420 463
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464=head2 Lexically scoped warning categories
465
466You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 467level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 468for details.
9d73390d 469
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470=head2 Lvalue subroutines
471
472WARNING: This is an experimental feature.
473
474change#4081
475[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
d4629d6a 476Tuomas Lukka <lukka@iki.fi>)]
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477
478=head2 "our" declarations
479
480An "our" declaration introduces a value that can be best understood
481as a lexically scoped symbolic alias to a global variable in the
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482package that was current where the variable was declared. This is
483mostly useful as an alternative to the C<vars> pragma, but also provides
484the opportunity to introduce typing and other attributes for such
485variables. See L<perlfunc/our>.
486
44dcb63b 487=head2 Support for strings represented as a vector of ordinals
16070b82 488
dd629d5b 489Literals of the form C<v1.2.3.4> are now parsed as a string composed of
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490of characters with the specified ordinals. This is an alternative, more
491readable way to construct (possibly unicode) strings instead of
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492interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
493C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
494parsed the same as C<v1.2.3>.
16070b82 495
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496Strings written in this form are also useful to represent version "numbers".
497It is easy to compare such version "numbers" (which are really just plain
498strings) using any of the usual string comparison operators C<eq>, C<ne>,
499C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
500C<&>, etc.
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501
502In conjunction with the new C<$^V> magic variable (which contains
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503the perl version as a string), such literals can be used as a readable way
504to check if you're running a particular version of Perl:
16070b82 505
44dcb63b 506 # this will parse in older versions of Perl also
16070b82 507 if ($^V and $^V gt v5.5.640) {
44dcb63b 508 # new features supported
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509 }
510
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511C<require> and C<use> also have some special magic to support such literals.
512They will be interpreted as a version rather than as a module name:
16070b82 513
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514 require v5.6.0; # croak if $^V lt v5.6.0
515 use v5.6.0; # same, but croaks at compile-time
a5222a85 516
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517Alternatively, the C<v> may be omitted if there is more than one dot:
518
519 require 5.6.0;
520 use 5.6.0;
521
44dcb63b 522Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
b22c7a20 523to print ordinals of characters in arbitrary strings:
1761cee5 524
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525 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
526 printf "%*vX", ":", $addr; # formats IPv6 address
dd629d5b 527 printf "%*vb", " ", $bits; # displays bitstring
1761cee5 528
191d61a7 529See L<perldata/"Scalar value constructors"> for additional information.
44dcb63b 530
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531=head2 Weak references
532
533WARNING: This is an experimental feature.
534
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535In previous versions of Perl, you couldn't cache objects so as
536to allow them to be deleted if the last reference from outside
537the cache is deleted. The reference in the cache would hold a
538reference count on the object and the objects would never be
539destroyed.
540
541Another familiar problem is with circular references. When an
542object references itself, its reference count would never go
543down to zero, and it would not get destroyed until the program
544is about to exit.
545
546Weak references solve this by allowing you to "weaken" any
547reference, that is, make it not count towards the reference count.
548When the last non-weak reference to an object is deleted, the object
549is destroyed and all the weak references to the object are
550automatically undef-ed.
a5222a85 551
d4629d6a
GS
552To use this feature, you need the WeakRef package from CPAN, which
553contains additional documentation.
554
555change#3385, also need perlguts documentation
556[TODO - Tuomas Lukka <lukka@iki.fi>]
a5222a85 557
becf2bd3
GS
558=head2 File globbing implemented internally
559
560WARNING: This is currently an experimental feature. Interfaces and
561implementation are likely to change.
562
52bb0670
GS
563Perl now uses the File::Glob implementation of the glob() operator
564automatically. This avoids using an external csh process and the
565problems associated with it.
becf2bd3 566
5fdc711f
GS
567=head2 Binary numbers supported
568
4f19785b
WSI
569Binary numbers are now supported as literals, in s?printf formats, and
570C<oct()>:
571
14218588
GS
572 $answer = 0b101010;
573 printf "The answer is: %b\n", oct("0b101010");
4f19785b 574
a5222a85
GS
575=head2 Some arrows may be omitted in calls through references
576
577Perl now allows the arrow to be omitted in many constructs
578involving subroutine calls through references. For example,
c47ff5f1 579C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
a5222a85 580This is rather similar to how the arrow may be omitted from
c47ff5f1
GS
581C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
582required for C<< foo(10)->('bar') >>.
a5222a85 583
afebc493
GS
584=head2 exists() is supported on subroutine names
585
586The exists() builtin now works on subroutine names. A subroutine
587is considered to exist if it has been declared (even if implicitly).
588See L<perlfunc/exists> for examples.
589
01020589
GS
590=head2 exists() and delete() are supported on array elements
591
592The exists() and delete() builtins now work on simple arrays as well.
593The behavior is similar to that on hash elements.
594
8ea97a1e 595exists() can be used to check whether an array element has been
8216c1fd
GS
596initialized. This avoids autovivifying array elements that don't exist.
597If the array is tied, the EXISTS() method in the corresponding tied
598package will be invoked.
8ea97a1e
GS
599
600delete() may be used to remove an element from the array and return
601it. The array element at that position returns to its unintialized
602state, so that testing for the same element with exists() will return
603false. If the element happens to be the one at the end, the size of
8216c1fd
GS
604the array also shrinks up to the highest element that tests true for
605exists(), or 0 if none such is found. If the array is tied, the DELETE()
606method in the corresponding tied package will be invoked.
01020589
GS
607
608See L<perlfunc/exists> and L<perlfunc/delete> for examples.
609
5fdc711f
GS
610=head2 syswrite() ease-of-use
611
a5222a85
GS
612The length argument of C<syswrite()> has become optional.
613
b1a9ed4a 614=head2 File and directory handles can be autovivified
a5222a85 615
c47ff5f1 616Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
b1a9ed4a
GS
617handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
618socket(), and accept()) now autovivify a file or directory handle
619if the handle passed to them is an uninitialized scalar variable. This
620allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
621to be used to create filehandles that will conveniently be closed
622automatically when the scope ends, provided there are no other references
623to them. This largely eliminates the need for typeglobs when opening
624filehandles that must be passed around, as in the following example:
a5222a85
GS
625
626 sub myopen {
627 open my $fh, "@_"
628 or die "Can't open '@_': $!";
629 return $fh;
630 }
631
632 {
633 my $f = myopen("</etc/motd");
634 print <$f>;
635 # $f implicitly closed here
636 }
637
6c67e1bb 638
5fdc711f
GS
639=head2 64-bit support
640
10cc9d2a
JH
641 NOTE: The Configure flags -Duselonglong and -Duse64bits
642 have been deprecated. Use -Duse64bitint instead.
643
644Any platform that has 64-bit integers either (a) natively as longs or
645ints (b) via special compiler flags (c) using long long are able to
9c107f78
JH
646use "quads" (64-integers) as follows:
647
648=over 4
649
a5222a85
GS
650=item *
651
652constants (decimal, hexadecimal, octal, binary) in the code
653
654=item *
9c107f78 655
a5222a85 656arguments to oct() and hex()
9c107f78 657
a5222a85
GS
658=item *
659
660arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
661
662=item *
9c107f78 663
a5222a85 664printed as such
9c107f78 665
a5222a85
GS
666=item *
667
668pack() and unpack() "q" and "Q" formats
669
670=item *
671
972b05a9
JH
672in basic arithmetics: + - * / % (NOTE: operating close to the limits
673of the integer values may produce surprising results)
a5222a85
GS
674
675=item *
1fad5d67 676
972b05a9
JH
677in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
678to be 32 bits wide.)
679
680=item *
681
682vec()
9c107f78
JH
683
684=back
685
686Note that unless you have the case (a) you will have to configure
10cc9d2a 687and compile Perl using the -Duse64bitint Configure flag.
9c107f78 688
49c10eea 689There are actually two modes of 64-bitness: the first one is achieved
10cc9d2a
JH
690using Configure -Duse64bitint and the second one using Configure
691-Duse64bitall. The difference is that the first one is minimal and
49c10eea
JH
692the second one maximal. The first one does only as much as is
693required to get 64-bit integers into Perl (this may mean, for example,
694using "long longs") while your memory may still be limited to 2
695gigabytes (because your pointers most likely are 32-bit); the second
696one goes all the way by attempting to switch also longs (and pointers)
697being 64-bit. This may create an even more binary incompatible Perl
10cc9d2a 698than -Duse64bitint: the resulting executable may not run at all in a
49c10eea
JH
699CPU-bit box, or you may have to reboot/reconfigure/rebuild your
700operating system to be 64-bit aware.
701
10cc9d2a
JH
702Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
703nor -Duse64bitall.
49c10eea 704
2d4389e4 705Last but not least: note that due to Perl's habit of always using
d0ba1bd2
JH
706floating point numbers the quads are still not true integers.
707When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
708-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
709are silently promoted to floating point numbers, after which they will
710start losing precision (their lower digits).
2d4389e4
JH
711
712=head2 Large file support
713
714If you have filesystems that support "large files" (files larger than
aa855319 7152 gigabytes), you may now also be able to create and access them from
249b38c6 716Perl. You have to use Configure -Duselargefiles. Turning on the
822ba51d
JH
717large file support turns on also the 64-bit support on many platforms.
718Beware that unless your filesystem also supports "sparse files" seeking
719to umpteen petabytes may be unadvisable.
2d4389e4 720
eed7fde4
JH
721Note that in addition to requiring a proper file system to do large
722files you may also need to adjust your per-process (or your
723per-system, or per-process-group, or per-user-group) maximum filesize
724limits before running Perl scripts that try to handle large files,
725especially if you intend to write such files.
726
727Finally, in addition to your process/process group maximum filesize
728limits, you may have quota limits on your filesystems that stop you
729(your user id or your user group id) from using large files.
730
731Adjusting your process/user/group/file system/operating system limits
732is outside the scope of Perl core language. For process limits, you
733may try increasing the limits using your shell's limits/limit/ulimit
734command before running Perl. The BSD::Resource extension (not
735included with the standard Perl distribution) may also be of use, it
736offers the getrlimit/setrlimit interface that can be used to adjust
737process resource usage limits, including the maximum filesize limit.
475d79b5 738
aa855319
JH
739=head2 Long doubles
740
741In some systems you may be able to use long doubles to enhance the
822ba51d 742range and precision of your double precision floating point numbers
aa855319
JH
743(that is, Perl's numbers). Use Configure -Duselongdouble to enable
744this support (if it is available).
745
746=head2 "more bits"
747
822ba51d 748You can "Configure -Dusemorebits" to turn on both the 64-bit support
aa855319 749and the long double support.
09bef843 750
43481408
GS
751=head2 Enhanced support for sort() subroutines
752
753Perl subroutines with a prototype of C<($$)> and XSUBs in general can
754now be used as sort subroutines. In either case, the two elements to
af365420 755be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
43481408
GS
756
757For unprototyped sort subroutines, the historical behavior of passing
758the elements to be compared as the global variables $a and $b remains
759unchanged.
760
62c18ce2
GS
761=head2 Better syntax checks on parenthesized unary operators
762
763Expressions such as:
764
14218588
GS
765 print defined(&foo,&bar,&baz);
766 print uc("foo","bar","baz");
767 undef($foo,&bar);
62c18ce2 768
7711098a 769used to be accidentally allowed in earlier versions, and produced
14218588
GS
770unpredictable behaviour. Some produced ancillary warnings
771when used in this way; others silently did the wrong thing.
62c18ce2
GS
772
773The parenthesized forms of most unary operators that expect a single
14218588
GS
774argument now ensure that they are not called with more than one
775argument, making the cases shown above syntax errors. The usual
776behaviour of:
62c18ce2 777
14218588
GS
778 print defined &foo, &bar, &baz;
779 print uc "foo", "bar", "baz";
780 undef $foo, &bar;
62c18ce2
GS
781
782remains unchanged. See L<perlop>.
783
3e3318e7
GS
784=head2 POSIX character class syntax [: :] supported
785
786For example to match alphabetic characters use /[[:alpha:]]/.
787See L<perlre> for details.
788
5a929a98 789=head2 Improved C<qw//> operator
8127e0e3 790
26ef7447
GS
791The C<qw//> operator is now evaluated at compile time into a true list
792instead of being replaced with a run time call to C<split()>. This
14218588
GS
793removes the confusing misbehaviour of C<qw//> in scalar context, which
794had inherited that behaviour from split().
26ef7447
GS
795
796Thus:
797
798 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
799
800now correctly prints "3|a", instead of "2|a".
8127e0e3 801
5a929a98
VU
802=head2 pack() format 'Z' supported
803
804The new format type 'Z' is useful for packing and unpacking null-terminated
805strings. See L<perlfunc/"pack">.
806
4d0c1c44 807=head2 pack() format modifier '!' supported
ee3907e2 808
14218588 809The new format type modifier '!' is useful for packing and unpacking
ee3907e2
JH
810native shorts, ints, and longs. See L<perlfunc/"pack">.
811
f29c64d6
GS
812=head2 pack() and unpack() support counted strings
813
a5222a85 814The template character '/' can be used to specify a counted string
f29c64d6
GS
815type to be packed or unpacked. See L<perlfunc/"pack">.
816
a5222a85
GS
817=head2 Comments in pack() templates
818
819The '#' character in a template introduces a comment up to
820end of the line. This facilitates documentation of pack()
821templates.
822
2b92dfce
GS
823=head2 $^X variables may now have names longer than one character
824
825Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
826error. Now variable names that begin with a control character may be
827arbitrarily long. However, for compatibility reasons, these variables
828I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 829C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
2b92dfce
GS
830than one control character, such as C<${^XY^Z}>, are illegal.
831
14218588
GS
832The old syntax has not changed. As before, `^X' may be either a
833literal control-X character or the two-character sequence `caret' plus
834`X'. When braces are omitted, the variable name stops after the
2b92dfce 835control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 836C<$^X . "YZ"> as before.
2b92dfce
GS
837
838As before, lexical variables may not have names beginning with control
839characters. As before, variables whose names begin with a control
14218588
GS
840character are always forced to be in package `main'. All such variables
841are reserved for future extensions, except those that begin with
09bef843 842C<^_>, which may be used by user programs and are guaranteed not to
14218588 843acquire special meaning in any future version of Perl.
2b92dfce 844
09bef843
SB
845=head2 C<use attrs> implicit in subroutine attributes
846
847Formerly, if you wanted to mark a subroutine as being a method call or
848as requiring an automatic lock() when it is entered, you had to declare
849that with a C<use attrs> pragma in the body of the subroutine.
16070b82 850That can now be accomplished with declaration syntax, like this:
09bef843 851
0120eecf 852 sub mymethod : locked method ;
09bef843 853 ...
16070b82
GS
854 sub mymethod : locked method {
855 ...
856 }
857
858 sub othermethod :locked :method ;
859 ...
860 sub othermethod :locked :method {
09bef843
SB
861 ...
862 }
863
16070b82
GS
864
865(Note how only the first C<:> is mandatory, and whitespace surrounding
866the C<:> is optional.)
867
09bef843
SB
868F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
869with the stubs they provide. See L<attributes>.
870
a5222a85
GS
871=head2 Regular expression improvements
872
873change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
874[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
875
876=head2 Overloading improvements
877
878change#2150
879[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
880
881=head2 open() with more than two arguments
882
883[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
884
885=head2 Support for interpolating named characters
886
887change#4052
888[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
889
a5222a85
GS
890=head2 C<require> and C<do> may be overridden
891
892C<require> and C<do 'file'> operations may be overridden locally
893by importing subroutines of the same name into the current package
894(or globally by importing them into the CORE::GLOBAL:: namespace).
895Overriding C<require> will also affect C<use>, provided the override
896is visible at compile-time.
897See L<perlsub/"Overriding Built-in Functions">.
898
899=head2 New variable $^C reflects C<-c> switch
900
08cd8952 901C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
902in compile-only mode (i.e. via the C<-c> switch). Since
903BEGIN blocks are executed under such conditions, this variable
904enables perl code to determine whether actions that make sense
905only during normal running are warranted. See L<perlvar>.
906
063663a9 907=head2 New variable $^V contains Perl version as a string
16070b82 908
da2094fd 909C<$^V> contains the Perl version number as a string composed of
063663a9
GS
910characters whose ordinals match the version numbers, e.g., v5.6.0.
911This may be used in string comparisons.
44dcb63b
GS
912
913See C<Support for strings represented as a vector of ordinals> for an
914example.
16070b82 915
a5222a85
GS
916=head2 Optional Y2K warnings
917
918If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
919it emits optional warnings when concatenating the number 19
920with another number.
921
922This behavior must be specifically enabled when running Configure.
b4bc034f 923See F<INSTALL> and F<README.Y2K>.
a5222a85 924
fbad3eb5
GS
925=head1 Significant bug fixes
926
c47ff5f1 927=head2 <HANDLE> on empty files
fbad3eb5 928
191f2cf3 929With C<$/> set to C<undef>, "slurping" an empty file returns a string of
14218588 930zero length (instead of C<undef>, as it used to) the first time the
191f2cf3
GS
931HANDLE is read after C<$/> is set to C<undef>. Further reads yield
932C<undef>.
fbad3eb5
GS
933
934This means that the following will append "foo" to an empty file (it used
14218588 935to do nothing):
fbad3eb5
GS
936
937 perl -0777 -pi -e 's/^/foo/' empty_file
938
14218588 939The behaviour of:
fbad3eb5
GS
940
941 perl -pi -e 's/^/foo/' empty_file
942
943is unchanged (it continues to leave the file empty).
944
0244c3a4
GS
945=head2 C<eval '...'> improvements
946
947Line numbers (as reflected by caller() and most diagnostics) within
948C<eval '...'> were often incorrect when here documents were involved.
949This has been corrected.
950
951Lexical lookups for variables appearing in C<eval '...'> within
952functions that were themselves called within an C<eval '...'> were
14218588
GS
953searching the wrong place for lexicals. The lexical search now
954correctly ends at the subroutine's block boundary.
0244c3a4
GS
955
956Parsing of here documents used to be flawed when they appeared as
957the replacement expression in C<eval 's/.../.../e'>. This has
958been fixed.
959
a5222a85
GS
960=head2 All compilation errors are true errors
961
962Some "errors" encountered at compile time were by neccessity
963generated as warnings followed by eventual termination of the
964program. This enabled more such errors to be reported in a
965single run, rather than causing a hard stop at the first error
966that was encountered.
967
968The mechanism for reporting such errors has been reimplemented
969to queue compile-time errors and report them at the end of the
970compilation as true errors rather than as warnings. This fixes
08cd8952
GS
971cases where error messages leaked through in the form of warnings
972when code was compiled at run time using C<eval STRING>, and
973also allows such errors to be reliably trapped using __DIE__ hooks.
a5222a85 974
45bc9206
GS
975=head2 Automatic flushing of output buffers
976
14218588
GS
977fork(), exec(), system(), qx//, and pipe open()s now flush buffers
978of all files opened for output when the operation
979was attempted. This mostly eliminates confusing
45bc9206 980buffering mishaps suffered by users unaware of how Perl internally
14218588 981handles I/O.
45bc9206 982
023ceb80
GS
983This is not supported on some platforms like Solaris where a suitably
984correct implementation of fflush(NULL) isn't available.
985
af8c498a
GS
986=head2 Better diagnostics on meaningless filehandle operations
987
c47ff5f1 988Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
af8c498a
GS
989are compile time errors. Attempting to read from filehandles that
990were opened only for writing will now produce warnings (just as
991writing to read-only filehandles does).
992
a5222a85
GS
993=head2 Where possible, buffered data discarded from duped input filehandle
994
c47ff5f1 995C<< open(NEW, "<&OLD") >> now attempts to discard any data that
a5222a85
GS
996was previously read and buffered in C<OLD> before duping the handle.
997On platforms where doing this is allowed, the next read operation
998on C<NEW> will return the same data as the corresponding operation
999on C<OLD>. Formerly, it would have returned the data from the start
1000of the following disk block instead.
1001
820475bd
GS
1002=head2 eof() has the same old magic as <>
1003
c47ff5f1 1004C<eof()> would return true if no attempt to read from C<< <> >> had
820475bd 1005yet been made. C<eof()> has been changed to have a little magic of its
c47ff5f1 1006own, it now opens the C<< <> >> files.
820475bd 1007
a5222a85
GS
1008=head2 system(), backticks and pipe open now reflect exec() failure
1009
1010On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1011etc., are implemented via fork() and exec(). When the underlying
1012exec() fails, earlier versions did not report the error properly,
1013since the exec() happened to be in a different process.
1014
1015The child process now communicates with the parent about the
437784d6 1016error in launching the external command, which allows these
a5222a85
GS
1017constructs to return with their usual error value and set $!.
1018
1019=head2 Implicitly closed filehandles are safer
1020
1021Sometimes implicitly closed filehandles (as when they are localized,
1022and Perl automatically closes them on exiting the scope) could
1023inadvertently set $? or $!. This has been corrected.
1024
1025=head2 C<(\$)> prototype and C<$foo{a}>
1026
1027An scalar reference prototype now correctly allows a hash or
1028array element in that slot.
1029
1030=head2 Pseudo-hashes work better
1031
1032Dereferencing some types of reference values in a pseudo-hash,
c47ff5f1 1033such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
a5222a85
GS
1034been corrected.
1035
1036When applied to a pseudo-hash element, exists() now reports whether
1037the specified value exists, not merely if the key is valid.
1038
01020589
GS
1039delete() now works on pseudo-hashes. When given a pseudo-hash element
1040or slice it deletes the values corresponding to the keys (but not the keys
1041themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1042
479ba383
GS
1043Pseudo-hash slices with constant keys are now optimized to array lookups
1044at compile-time.
1045
1046The C<fields> pragma now provides ways to create pseudo-hashes, via
1047fields::new() and fields::phash(). See L<fields>.
1048
a5222a85
GS
1049=head2 C<goto &sub> and AUTOLOAD
1050
08cd8952 1051The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
1052to be autoloaded.
1053
1054=head2 C<-bareword> allowed under C<use integer>
1055
1056The autoquoting of barewords preceded by C<-> did not work
1057in prior versions when the C<integer> pragma was enabled.
1058This has been fixed.
1059
1060=head2 Boolean assignment operators are legal lvalues
1061
1062Constructs such as C<($a ||= 2) += 1> are now allowed.
1063
1064=head2 C<sort $coderef @foo> allowed
1065
1066sort() did not accept a subroutine reference as the comparison
08cd8952 1067function in earlier versions. This is now permitted.
a5222a85
GS
1068
1069=head2 Failures in DESTROY()
1070
1071When code in a destructor threw an exception, it went unnoticed
1072in earlier versions of Perl, unless someone happened to be
1073looking in $@ just after the point the destructor happened to
1074run. Such failures are now visible as warnings when warnings are
1075enabled.
1076
1077=head2 Locale bugs fixed
54195c32 1078
437784d6 1079printf() and sprintf() previously reset the numeric locale
67d3893f
JH
1080back to the default "C" locale. This has been fixed.
1081
1082Numbers formatted according to the local numeric locale
1083(such as using a decimal comma instead of a decimal dot) caused
1084"isn't numeric" warnings, even while the operations accessing
1085those numbers produced correct results. The warnings are gone.
54195c32 1086
a5222a85
GS
1087=head2 Memory leaks
1088
1089The C<eval 'return sub {...}'> construct could sometimes leak
1090memory. This has been fixed.
1091
1092Operations that aren't filehandle constructors used to leak memory
1093when used on invalid filehandles. This has been fixed.
1094
1095Constructs that modified C<@_> could fail to deallocate values
1096in C<@_> and thus leak memory. This has been corrected.
1097
1098=head2 Spurious subroutine stubs after failed subroutine calls
1099
1100Perl could sometimes create empty subroutine stubs when a
1101subroutine was not found in the package. Such cases stopped
1102later method lookups from progressing into base packages.
1103This has been corrected.
1104
1105=head2 Consistent numeric conversions
1106
1107change#3378,3318
1108[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1109
1110=head2 Taint failures under C<-U>
1111
1112When running in unsafe mode, taint violations could sometimes
1113cause silent failures. This has been fixed.
1114
1115=head2 END blocks and the C<-c> switch
1116
1117Prior versions used to run BEGIN B<and> END blocks when Perl was
1118run in compile-only mode. Since this is typically not the expected
08cd8952 1119behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
1120is used.
1121
7d30b5c4 1122See L<CHECK blocks> for how to run things when the compile phase ends.
a5222a85
GS
1123
1124=head2 Potential to leak DATA filehandles
1125
1126Using the C<__DATA__> token creates an implicit filehandle to
1127the file that contains the token. It is the program's
1128responsibility to close it when it is done reading from it.
1129
1130This caveat is now better explained in the documentation.
1131See L<perldata>.
1132
1133=head2 Diagnostics follow STDERR
1134
1135Diagnostic output now goes to whichever file the C<STDERR> handle
1136is pointing at, instead of always going to the underlying C runtime
1137library's C<stderr>.
1138
1139=head2 Other fixes for better diagnostics
1140
437784d6 1141Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
1142during the global destruction phase.
1143
1144Diagnostics emitted from code running in threads other than the main
1145thread are now accompanied by the thread ID.
1146
1147Embedded null characters in diagnostics now actually show up. They
1148used to truncate the message in prior versions.
1149
1150$foo::a and $foo::b are now exempt from "possible typo" warnings only
1151if sort() is encountered in package foo.
1152
501fbaef 1153Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
1154constructs now generate a warning, since they may take on new
1155semantics in later versions of Perl.
1156
1157=head1 Performance enhancements
1158
1159=head2 Simple sort() using { $a <=> $b } and the like are optimized
1160
08cd8952 1161Many common sort() operations using a simple inlined block are now
a5222a85
GS
1162optimized for faster performance.
1163
1164=head2 Optimized assignments to lexical variables
1165
1166Certain operations in the RHS of assignment statements have been
1167optimized to directly set the lexical variable on the LHS,
1168eliminating redundant copying overheads.
1169
a5222a85
GS
1170=head2 Faster mechanism to invoke XSUBs
1171
1172change#4044,4125
1173[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1174
1175=head2 Perl_malloc() improvements
1176
1177change#4237
1178[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1179
1180=head2 Faster subroutine calls
1181
1182Minor changes in how subroutine calls are handled internally
1183provide marginal improvements in performance.
1184
1185=head1 Platform specific changes
1186
063663a9 1187=head2 Supported platforms
ba8251e8 1188
5fdc711f
GS
1189=over 4
1190
1191=item *
1192
6c67e1bb
TC
1193VM/ESA is now supported.
1194
5fdc711f
GS
1195=item *
1196
ee3907e2
JH
1197Siemens BS2000 is now supported under the POSIX Shell.
1198
1199=item *
1200
2bb14304
JH
1201The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1202extension.
6c67e1bb 1203
5fdc711f
GS
1204=item *
1205
ee3907e2 1206GNU/Hurd is now supported.
6c67e1bb 1207
00ad96e1
JH
1208=item *
1209
063663a9 1210Rhapsody/Darwin is now supported.
00ad96e1 1211
27806c82
JH
1212=item *
1213
1214EPOC is is now supported (on Psion 5).
1215
5fdc711f
GS
1216=back
1217
a5222a85
GS
1218=head2 DOS
1219
d524f05e
LM
1220=over 4
1221
1222=item *
1223
1224Perl now works with djgpp 2.02 (and 2.03 alpha).
1225
1226=item *
1227
1228Environment variable names are not converted to uppercase any more.
1229
1230=item *
1231
1232Wrong exit code from backticks now fixed.
1233
1234=item *
1235
1236This port is still using its own builtin globbing.
1237
1238=back
a5222a85
GS
1239
1240=head2 OS/2
1241
1242[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1243
c6018dae 1244=head2 OS390 (OpenEdition MVS)
063663a9
GS
1245
1246Support for this EBCDIC platform has not been renewed in this release.
1247There are difficulties in reconciling Perl's standardization on UTF-8
1248as its internal representation for characters with the EBCDIC character
1249set, because the two are incompatible.
1250
1251It is unclear whether future versions will renew support for this
1252platform, but the possibility exists.
1253
a5222a85
GS
1254=head2 VMS
1255
c93fa817
GS
1256Numerous revisions and extensions to configuration, build, testing, and
1257installation process to accomodate core changes and VMS-specific options
1258
1259Expand %ENV-handling code to allow runtime mapping to logical names,
1260CLI symbols, and CRTL environ array
1261
1262Extension of subprocess invocation code to accept filespecs as command "verbs"
1263
1264Add to Perl command line processing the ability to use default file types and
1265to recognize Unix-style C<2E<gt>&1>.
1266
1267Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS
1268
1269Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly
1270
1271Barewords at start of Unix-syntax paths may be treated as text rather than
1272only as logical names
1273
1274Optional secure translation of several logical names used internally by Perl
1275
1276Miscellaneous bugfixing and porting of new core code to VMS
1277
1278Thanks are gladly extended to the many people who have contributed VMS
1279patches, testing, and ideas.
a5222a85
GS
1280
1281=head2 Win32
1282
1283Site library searches failed to look for ".../site/5.XXX/lib"
1284if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1285
1286When given a pathname that consists only of a drivename, such
1287as C<A:>, opendir() and stat() now use the current working
1288directory for the drive rather than the drive root.
1289
1290The builtin XSUB functions in the Win32:: namespace are
1291documented. See L<Win32>.
1292
1293$^X now contains the full path name of the running executable.
1294
1295A Win32::GetLongPathName() function is provided to complement
1296Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1297
1298POSIX::uname() is supported.
1299
1300system(1,...) now returns true process IDs rather than process
1301handles. kill() accepts any real process id, rather than strictly
1302return values from system(1,...).
1303
42b8b86c
GS
1304For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1305test whether a process exists.
1306
a5222a85
GS
1307The C<Shell> module is supported.
1308
883d36a6
GS
1309Rudimentary support for building under command.com in Windows 95
1310has been added.
1311
c39cd008
GS
1312Scripts are read in binary mode by default to allow ByteLoader (and
1313the filter mechanism in general) to work properly. For compatibility,
53129d29
GS
1314the DATA filehandle will be set to text mode if a carriage return is
1315detected at the end of the line containing the __END__ or __DATA__
1316token; if not, the DATA filehandle will be left open in binary mode.
1317Earlier versions always opened the DATA filehandle in text mode.
c39cd008 1318
3a4b19e4 1319The glob() operator is implemented via the C<File::Glob> extension,
8004f2ac 1320which supports glob syntax of the C shell. This increases the flexibility
16070b82
GS
1321of the glob() operator, but there may be compatibility issues for
1322programs that relied on the older globbing syntax. If you want to
1323preserve compatibility with the older syntax, you might want to put
1324a C<use File::DosGlob;> in your program. For details and compatibility
1325information, see L<File::Glob>.
1326
a5222a85
GS
1327[TODO - GSAR]
1328
6c67e1bb
TC
1329=head1 New tests
1330
1331=over 4
1332
09bef843
SB
1333=item lib/attrs
1334
1335Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1336
2675e62c
GS
1337=item lib/env
1338
1339Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1340
1341=item lib/env-array
1342
1343Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1344
09bef843 1345=item lib/io_const
6c67e1bb
TC
1346
1347IO constants (SEEK_*, _IO*).
14218588 1348
09bef843 1349=item lib/io_dir
6c67e1bb
TC
1350
1351Directory-related IO methods (new, read, close, rewind, tied delete).
1352
09bef843 1353=item lib/io_multihomed
6c67e1bb
TC
1354
1355INET sockets with multi-homed hosts.
1356
09bef843 1357=item lib/io_poll
6c67e1bb
TC
1358
1359IO poll().
1360
09bef843 1361=item lib/io_unix
6c67e1bb
TC
1362
1363UNIX sockets.
1364
09bef843
SB
1365=item op/attrs
1366
1367Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1368
6c67e1bb
TC
1369=item op/filetest
1370
1371File test operators.
1372
1373=item op/lex_assign
1374
5fdc711f 1375Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb 1376
afebc493
GS
1377=item op/exists_sub
1378
1379Verify C<exists &sub> operations.
1380
6c67e1bb 1381=back
e02fdbd2 1382
ba8251e8
GS
1383=head1 Modules and Pragmata
1384
3e8c4fa0
JH
1385=head2 Modules
1386
b7d8191e
JH
1387=over 4
1388
09bef843
SB
1389=item attributes
1390
1391While used internally by Perl as a pragma, this module also
1392provides a way to fetch subroutine and variable attributes.
1393See L<attributes>.
1394
a5222a85
GS
1395=item B
1396
c6018dae
GS
1397WARNING: The Compiler suite is still highly experimental. The
1398generated code may not be correct, even it manages to execute
1399without errors.
501fbaef 1400
c6018dae
GS
1401The Perl Compiler suite has been extensively reworked for this
1402release. More of the standard Perl testsuite passes when run
1403under the Compiler, but there is still a significant way to
1404go to achieve production quality compiled executables.
a5222a85 1405
f29c64d6
GS
1406=item ByteLoader
1407
a5222a85 1408The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1409Perl bytecode. See L<ByteLoader>.
1410
a5222a85
GS
1411=item constant
1412
83763826
GS
1413References can now be used.
1414
1415The new version also allows a leading underscore in constant names, but
1416disallows a double leading underscore (as in "__LINE__"). Some other names
1417are disallowed or warned against, including BEGIN, END, etc. Some names
1418which were forced into main:: used to fail silently in some cases; now they're
1419fatal (outside of main::) and an optional warning (inside of main::).
1420The ability to detect whether a constant had been set with a given name has
1421been added.
1422
1423See L<constant>.
a5222a85
GS
1424
1425=item charnames
1426
1427change#4052
1428[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1429
1430=item Data::Dumper
1431
1432A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1433too deeply into deep data structures. See L<Data::Dumper>.
a5222a85 1434
0f1923bd
GS
1435The XSUB implementation of Dump() is now automatically called if the
1436C<Useqq> setting is not in use.
1437
a5222a85
GS
1438Dumping C<qr//> objects works correctly.
1439
1440=item DB
1441
1442C<DB> is an experimental module that exposes a clean abstraction
1443to Perl's debugging API.
1444
1445=item DB_File
1446
0536e0eb
GS
1447DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1448See C<ext/DB_File/Changes>.
a5222a85 1449
f29c64d6
GS
1450=item Devel::DProf
1451
9e107c59
GS
1452Devel::DProf, a Perl source code profiler has been added. See
1453L<Devel::DProf> and L<dprofpp>.
f29c64d6 1454
b7d8191e
JH
1455=item Dumpvalue
1456
437784d6 1457The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1458
1459=item Benchmark
1460
54e82ce5
GS
1461Overall, Benchmark results exhibit lower average error and better timing
1462accuracy.
1463
868cb350 1464You can now run tests for I<n> seconds instead of guessing the right
14218588
GS
1465number of tests to run: e.g. timethese(-5, ...) will run each
1466code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1467means "for at least 3 CPU seconds". The output format has also
14218588 1468changed. For example:
155776c0 1469
54e82ce5 1470 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1471
1472will now output something like this:
1473
54e82ce5
GS
1474 Benchmark: running a, b, each for at least 5 CPU seconds...
1475 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1476 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1477
1478New features: "each for at least N CPU seconds...", "wallclock secs",
1479and the "@ operations/CPU second (n=operations)".
b7d8191e 1480
54e82ce5
GS
1481timethese() now returns a reference to a hash of Benchmark objects containing
1482the test results, keyed on the names of the tests.
1483
1484timethis() now returns the iterations field in the Benchmark result object
1485instead of 0.
1486
1487timethese(), timethis(), and the new cmpthese() (see below) can also take
1488a format specifier of 'none' to suppress output.
1489
1490A new function countit() is just like timeit() except that it takes a
1491TIME instead of a COUNT.
1492
1493A new function cmpthese() prints a chart comparing the results of each test
1494returned from a timethese() call. For each possible pair of tests, the
1495percentage speed difference (iters/sec or seconds/iter) is shown.
1496
1497For other details, see L<Benchmark>.
a5222a85 1498
f505c983
GS
1499=item Devel::Peek
1500
1501The Devel::Peek module provides access to the internal representation
14218588 1502of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1503
44dcb63b
GS
1504=item English
1505
1506$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1507(a numeric value).
1508
2675e62c
GS
1509=item Env
1510
1511Env now supports accessing environment variables like PATH as array
1512variables.
1513
a5222a85
GS
1514=item ExtUtils::MakeMaker
1515
1516change#4135, also needs docs in module pod
1517[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1518
b7d8191e
JH
1519=item Fcntl
1520
1521More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
822ba51d
JH
1522large file (more than 4GB) access Note that the O_LARGEFILE is
1523automatically/transparently added to sysopen() flags if large file
1524support has been configured), Free/Net/OpenBSD locking behaviour flags
1525F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
ca6e1c26
JH
1526O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1527SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1528The chmod()/stat() S_IF* constants and S_IS* functions are available
1529via the C<:mode> tag.
1530
b7d8191e 1531
a5222a85
GS
1532=item File::Compare
1533
1534A compare_text() function has been added, which allows custom
1535comparison functions. See L<File::Compare>.
1536
1537=item File::Find
1538
1539File::Find now works correctly when the wanted() function is either
1540autoloaded or is a symbolic reference.
1541
08cd8952 1542A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1543when pruning top-level directories has been fixed.
1544
81793b90
GS
1545File::Find now also supports several other options to control its
1546behavior. It can follow symbolic links if the C<follow> option is
1547specified. Enabling the C<no_chdir> option will make File::Find skip
1548changing the current directory when walking directories. The C<untaint>
1549flag can be useful when running with taint checks enabled.
1550
1551See L<File::Find>.
1552
becf2bd3
GS
1553=item File::Glob
1554
52bb0670
GS
1555This extension implements BSD-style file globbing. By default,
1556it will also be used for the internal implementation of the glob()
1557operator. See L<File::Glob>.
becf2bd3 1558
f505c983
GS
1559=item File::Spec
1560
1561New methods have been added to the File::Spec module: devnull() returns
19799a22 1562the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1563the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1564to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1565rel2abs(). For compatibility with operating systems that specify volume
1566names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1567have been added.
1568
1569=item File::Spec::Functions
1570
1571The new File::Spec::Functions modules provides a function interface
14218588 1572to the File::Spec module. Allows shorthand
f505c983 1573
14218588 1574 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1575
1576instead of
1577
14218588 1578 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1579
a5222a85
GS
1580=item Getopt::Long
1581
c6edd1b7
GS
1582Getopt::Long licensing has changed to allow the Perl Artistic License
1583as well as the GPL. It used to be GPL only, which got in the way of
1584non-GPL applications that wanted to use Getopt::Long.
1585
1586Getopt::Long encourages the use of Pod::Usage to produce help
1587messages. For example:
1588
1589 use Getopt::Long;
1590 use Pod::Usage;
1591 my $man = 0;
1592 my $help = 0;
1593 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1594 pod2usage(1) if $help;
1595 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1596
1597 __END__
1598
1599 =head1 NAME
1600
1601 sample - Using GetOpt::Long and Pod::Usage
1602
1603 =head1 SYNOPSIS
1604
1605 sample [options] [file ...]
1606
1607 Options:
1608 -help brief help message
1609 -man full documentation
1610
1611 =head1 OPTIONS
1612
1613 =over 8
1614
1615 =item B<-help>
1616
1617 Print a brief help message and exits.
1618
1619 =item B<-man>
1620
1621 Prints the manual page and exits.
1622
1623 =back
1624
1625 =head1 DESCRIPTION
1626
1627 B<This program> will read the given input file(s) and do someting
1628 useful with the contents thereof.
1629
1630 =cut
1631
1632See L<Pod::Usage> for details.
1633
c47ff5f1 1634A bug that prevented the non-option call-back <> from being
c6edd1b7
GS
1635specified as the first argument has been fixed.
1636
c47ff5f1
GS
1637To specify the characters < and > as option starters, use ><. Note,
1638however, that changing option starters is strongly deprecated.
a5222a85
GS
1639
1640=item IO
1641
1642write() and syswrite() will now accept a single-argument
1643form of the call, for consistency with Perl's syswrite().
1644
1645You can now create a TCP-based IO::Socket::INET without forcing
1646a connect attempt. This allows you to configure its options
1647(like making it non-blocking) and then call connect() manually.
1648
1649A bug that prevented the IO::Socket::protocol() accessor
1650from ever returning the correct value has been corrected.
1651
36f31b50
GS
1652IO::Socket::connect now uses non-blocking IO instead of alarm()
1653to do connect timeouts.
1654
1655IO::Socket::accept now uses select() instead of alarm() for doing
1656timeouts.
1657
1658IO::Socket::INET->new now sets $! correctly on failure. $@ is
1659still set for backwards compatability.
1660
a5222a85
GS
1661=item JPL
1662
1663Java Perl Lingo is now distributed with Perl. See jpl/README
1664for more information.
1665
883d36a6
GS
1666=item lib
1667
1668C<use lib> now weeds out any trailing duplicate entries.
1669C<no lib> removes all named entries.
1670
e16b8f49
WM
1671=item Math::BigInt
1672
c47ff5f1 1673The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
e16b8f49
WM
1674and C<~> are now supported on bigints.
1675
b7d8191e 1676=item Math::Complex
7711098a 1677
14218588 1678The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1679act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e 1680
16357284
JH
1681The class method C<display_format> and the corresponding object method
1682C<display_format>, in addition to accepting just one argument, now can
1683also accept a parameter hash. Recognized keys of a parameter hash are
1684C<"style">, which corresponds to the old one parameter case, and two
1685new parameters: C<"format">, which is a printf()-style format string
1686(defaults usually to C<"%.15g">, you can revert to the default by
1687setting the format string to C<undef>) used for both parts of a
1688complex number, and C<"polar_pretty_print"> (defaults to true),
1689which controls whether an attempt is made to try to recognize small
1690multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1691polar complex number.
1692
1693The potentially disruptive change is that in list context both methods
1694now I<return the parameter hash>, instead of only the value of the
1695C<"style"> parameter.
1696
b7d8191e
JH
1697=item Math::Trig
1698
14218588
GS
1699A little bit of radial trigonometry (cylindrical and spherical),
1700radial coordinate conversions, and the great circle distance were added.
b7d8191e 1701
1761cee5 1702=item Pod::Parser, Pod::InputObjects
d4629d6a 1703
1761cee5
JH
1704Pod::Parser is a base class for parsing and selecting sections of
1705pod documentation from an input stream. This module takes care of
1706identifying pod paragraphs and commands in the input and hands off the
1707parsed paragraphs and commands to user-defined methods which are free
1708to interpret or translate them as they see fit.
d4629d6a
GS
1709
1710Pod::InputObjects defines some input objects needed by Pod::Parser, and
1711for advanced users of Pod::Parser that need more about a command besides
1761cee5 1712its name and text.
d4629d6a
GS
1713
1714As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1715"base parser code" recommended for use by all pod2xxx translators.
1716Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1761cee5
JH
1717to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1718underway. For any questions or comments about pod parsing and translating
1719issues and utilities, please use the pod-people@perl.org mailing list.
d4629d6a 1720
1761cee5 1721For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
d4629d6a 1722
1761cee5 1723=item Pod::Checker, podchecker
d4629d6a 1724
1761cee5
JH
1725This utility checks pod files for correct syntax, according to
1726L<perlpod>. Obvious errors are flagged as such, while warnings are
1727printed for mistakes that can be handled gracefully. The checklist is
1728not complete yet. See L<Pod::Checker>.
d4629d6a 1729
1761cee5 1730=item Pod::ParseUtils, Pod::Find
d4629d6a 1731
1761cee5
JH
1732These modules provide a set of gizmos that are useful mainly for pod
1733translators. L<Pod::Find|Pod::Find> traverses directory structures and
1734returns found pod files, along with their canonical names (like
1735C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1736B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
c47ff5f1 1737(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1761cee5 1738(for caching information about pod files, e.g. link nodes).
d4629d6a 1739
1761cee5 1740=item Pod::Select, podselect
d4629d6a 1741
1761cee5
JH
1742Pod::Select is a subclass of Pod::Parser which provides a function
1743named "podselect()" to filter out user-specified sections of raw pod
1744documentation from an input stream. podselect is a script that provides
1745access to Pod::Select from other scripts to be used as a filter.
1746See L<Pod::Select>.
d4629d6a 1747
1761cee5 1748=item Pod::Usage, pod2usage
d4629d6a 1749
1761cee5
JH
1750Pod::Usage provides the function "pod2usage()" to print usage messages for
1751a Perl script based on its embedded pod documentation. The pod2usage()
1752function is generally useful to all script authors since it lets them
1753write and maintain a single source (the pods) for documentation, thus
1754removing the need to create and maintain redundant usage message text
1755consisting of information already in the pods.
d4629d6a 1756
1761cee5
JH
1757There is also a pod2usage script which can be used from other kinds of
1758scripts to print usage messages from pods (even for non-Perl scripts
1759with pods embedded in comments).
a5222a85 1760
1761cee5 1761For details and examples, please see L<Pod::Usage>.
a5222a85
GS
1762
1763=item Pod::Text and Pod::Man
1764
e3e5e1ea
GS
1765Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1766still available for backwards compatibility, the module now has a new
1767preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1768module is easily subclassed for tweaks to the output, and two such
1769subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1770using termcap information, and Pod::Text::Color for markup with ANSI color
1771sequences) are now standard.
1772
1773pod2man has been turned into a module, Pod::Man, which also uses
1774Pod::Parser. In the process, several outstanding bugs related to quotes
1775in section headers, quoting of code escapes, and nested lists have been
1776fixed. pod2man is now a wrapper script around this module.
a5222a85 1777
f4b9d880
RA
1778=item SDBM_File
1779
1780An EXISTS method has been added to this module (and sdbm_exists() has
1781been added to the underlying sdbm library), so one can now call exists
14218588 1782on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1783runtime error.
1784
a5222a85
GS
1785A bug that may have caused data loss when more than one disk block
1786happens to be read from the database in a single FETCH() has been
1787fixed.
1788
8ce86de8
GS
1789=item Sys::Syslog
1790
1791Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1792no longer requires syslog.ph to exist.
1793
f91101c9
GS
1794=item Sys::Hostname
1795
1796Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1797uname() if they exist.
1798
e3e5e1ea
GS
1799=item Term::ANSIColor
1800
1801Term::ANSIColor is a very simple module to provide easy and readable
1802access to the ANSI color and highlighting escape sequences, supported by
1803most ANSI terminal emulators. It is now included standard.
1804
06ef4121
PC
1805=item Time::Local
1806
1807The timelocal() and timegm() functions used to silently return bogus
437784d6 1808results when the date fell outside the machine's integer range. They
a5222a85 1809now consistently croak() if the date falls in an unsupported range.
06ef4121 1810
8fe0a5c4
JD
1811=item Win32
1812
1813The error return value in list context has been changed for all functions
14218588
GS
1814that return a list of values. Previously these functions returned a list
1815with a single element C<undef> if an error occurred. Now these functions
1816return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1817functions:
1818
14218588
GS
1819 Win32::FsType
1820 Win32::GetOSVersion
8fe0a5c4
JD
1821
1822The remaining functions are unchanged and continue to return C<undef> on
1823error even in list context.
1824
1825The Win32::SetLastError(ERROR) function has been added as a complement
1826to the Win32::GetLastError() function.
1827
1828The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1829pathname for FILENAME in scalar context. In list context it returns
1830a two-element list containing the fully qualified directory name and
501fbaef 1831the filename. See L<Win32>.
8fe0a5c4 1832
9fe6733a
PM
1833=item DBM Filters
1834
1835A new feature called "DBM Filters" has been added to all the
14218588
GS
1836DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1837DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1838
1839 filter_store_key
1840 filter_store_value
1841 filter_fetch_key
1842 filter_fetch_value
1843
14218588 1844These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1845written to the database or just after they are read from the database.
1846See L<perldbmfilter> for further information.
1847
b7d8191e 1848=back
3e8c4fa0
JH
1849
1850=head2 Pragmata
1851
437784d6 1852C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1853backward-compatibility. It's been replaced by the C<sub : attributes>
1854syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1855
14218588 1856C<use utf8> to enable UTF-8 and Unicode support.
43165c05 1857
4438c4b7 1858Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1859See L<perllexwarn>.
6c67e1bb 1860
67d3893f
JH
1861C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1862...). Currently only one subpragma implemented, "use filetest
1863'access';", that uses access(2) or equivalent to check permissions
1864instead of using stat(2) as usual. This matters in filesystems
1865where there are ACLs (access control lists): the stat(2) might lie,
1866but access(2) knows better.
6c67e1bb 1867
ba8251e8
GS
1868=head1 Utility Changes
1869
a5222a85
GS
1870=head2 h2ph
1871
1872[TODO - Kurt Starsinic <kstar@chapin.edu>]
1873
1874=head2 perlcc
1875
1876C<perlcc> now supports the C and Bytecode backends. By default,
1877it generates output from the simple C backend rather than the
1878optimized C backend.
1879
1880Support for non-Unix platforms has been improved.
1881
1882=head2 h2xs
1883
1884change#4232
1885[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
e02fdbd2 1886
ba8251e8
GS
1887=head1 Documentation Changes
1888
5fdc711f
GS
1889=over 4
1890
954c1994
GS
1891=item perlapi.pod
1892
1893The official list of public Perl API functions.
1894
883d36a6
GS
1895=item perlcompile.pod
1896
1897An introduction to using the Perl Compiler suite.
1898
c7c04614
GS
1899=item perlfilter.pod
1900
1901An introduction to writing Perl source filters.
1902
883d36a6
GS
1903=item perlhack.pod
1904
1905Some guidelines for hacking the Perl source code.
1906
954c1994
GS
1907=item perlintern.pod
1908
1909A list of internal functions in the Perl source code.
1910(List is currently empty.)
1911
5fdc711f 1912=item perlopentut.pod
f8284313 1913
5fdc711f
GS
1914A tutorial on using open() effectively.
1915
1916=item perlreftut.pod
1917
1918A tutorial that introduces the essentials of references.
1919
694468e3
GS
1920=item perlboot.pod
1921
1922A tutorial for beginners on object-oriented Perl.
1923
14218588
GS
1924=item perltootc.pod
1925
1926A tutorial on managing class data for object modules.
1927
393fec97
GS
1928=item perlunicode.pod
1929
1930An introduction to Unicode support features in Perl.
1931
5fdc711f 1932=back
e02fdbd2 1933
73b437c8 1934=head1 New or Changed Diagnostics
ba8251e8 1935
a99ba403
GS
1936=over 4
1937
56e90b21
GS
1938=item "%s" variable %s masks earlier declaration in same %s
1939
1940(W) A "my" or "our" variable has been redeclared in the current scope or statement,
1941effectively eliminating all access to the previous instance. This is almost
1942always a typographical error. Note that the earlier variable will still exist
1943until the end of the scope or until all closure referents to it are
1944destroyed.
1945
33633739
GS
1946=item "my sub" not yet implemented
1947
1948(F) Lexically scoped subroutines are not yet implemented. Don't try that
1949yet.
1950
1951=item "our" variable %s redeclared
1952
1953(W) You seem to have already declared the same global once before in the
1954current lexical scope.
1955
a99ba403
GS
1956=item '!' allowed only after types %s
1957
1958(F) The '!' is allowed in pack() and unpack() only after certain types.
1959See L<perlfunc/pack>.
1960
1961=item / cannot take a count
1962
1963(F) You had an unpack template indicating a counted-length string,
1964but you have also specified an explicit size for the string.
1965See L<perlfunc/pack>.
1966
1967=item / must be followed by a, A or Z
1968
1969(F) You had an unpack template indicating a counted-length string,
1970which must be followed by one of the letters a, A or Z
1971to indicate what sort of string is to be unpacked.
1972See L<perlfunc/pack>.
1973
1974=item / must be followed by a*, A* or Z*
1975
437784d6 1976(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1977Currently the only things that can have their length counted are a*, A* or Z*.
1978See L<perlfunc/pack>.
1979
1980=item / must follow a numeric type
1981
1982(F) You had an unpack template that contained a '#',
1983but this did not follow some numeric unpack specification.
1984See L<perlfunc/pack>.
1985
a99ba403
GS
1986=item /%s/: Unrecognized escape \\%c passed through
1987
1988(W) You used a backslash-character combination which is not recognized
1989by Perl. This combination appears in an interpolated variable or a
1028017a
JH
1990C<'>-delimited regular expression. The character was understood literally.
1991
1992=item /%s/: Unrecognized escape \\%c in character class passed through
1993
1994(W) You used a backslash-character combination which is not recognized
1995by Perl inside character classes. The character was understood literally.
a99ba403
GS
1996
1997=item /%s/ should probably be written as "%s"
1998
1999(W) You have used a pattern where Perl expected to find a string,
437784d6 2000as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
2001or false result of matching the pattern against $_ as the string,
2002which is probably not what you had in mind.
2003
2004=item %s() called too early to check prototype
2005
2006(W) You've called a function that has a prototype before the parser saw a
2007definition or declaration for it, and Perl could not check that the call
2008conforms to the prototype. You need to either add an early prototype
2009declaration for the subroutine in question, or move the subroutine
2010definition ahead of the call to get proper prototype checking. Alternatively,
2011if you are certain that you're calling the function correctly, you may put
2012an ampersand before the name to avoid the warning. See L<perlsub>.
2013
56e90b21
GS
2014=item %s argument is not a HASH or ARRAY element
2015
2016(F) The argument to exists() must be a hash or array element, such as:
2017
2018 $foo{$bar}
2019 $ref->[12]->["susie"]
2020
2021=item %s argument is not a HASH or ARRAY element or slice
2022
2023(F) The argument to delete() must be either a hash or array element, such as:
2024
2025 $foo{$bar}
2026 $ref->[12]->["susie"]
2027
2028or a hash or array slice, such as:
2029
2030 @foo[$bar, $baz, $xyzzy]
2031 @{$ref->[12]}{"susie", "queue"}
2032
afebc493
GS
2033=item %s argument is not a subroutine name
2034
2035(F) The argument to exists() for C<exists &sub> must be a subroutine
2036name, and not a subroutine call. C<exists &sub()> will generate this error.
2037
09bef843
SB
2038=item %s package attribute may clash with future reserved word: %s
2039
2040(W) A lowercase attribute name was used that had a package-specific handler.
2041That name might have a meaning to Perl itself some day, even though it
2042doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2043See L<attributes>.
2044
a99ba403 2045=item (in cleanup) %s
6b121555 2046
a99ba403
GS
2047(W) This prefix usually indicates that a DESTROY() method raised
2048the indicated exception. Since destructors are usually called by
2049the system at arbitrary points during execution, and often a vast
2050number of times, the warning is issued only once for any number
2051of failures that would otherwise result in the same message being
2052repeated.
2053
2054Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2055could also result in this warning. See L<perlcall/G_KEEPERR>.
2056
2057=item <> should be quotes
2058
c47ff5f1 2059(F) You wrote C<< require <file> >> when you should have written
a99ba403
GS
2060C<require 'file'>.
2061
2062=item Attempt to join self
2063
2064(F) You tried to join a thread from within itself, which is an
2065impossible task. You may be joining the wrong thread, or you may
2066need to move the join() to some other thread.
2067
2068=item Bad evalled substitution pattern
2069
2070(F) You've used the /e switch to evaluate the replacement for a
2071substitution, but perl found a syntax error in the code to evaluate,
2072most likely an unexpected right brace '}'.
2073
2074=item Bad realloc() ignored
2075
2076(S) An internal routine called realloc() on something that had never been
2077malloc()ed in the first place. Mandatory, but can be disabled by
2078setting environment variable C<PERL_BADFREE> to 1.
2079
34d09196
GS
2080=item Bareword found in conditional
2081
2082(W) The compiler found a bareword where it expected a conditional,
2083which often indicates that an || or && was parsed as part of the
2084last argument of the previous construct, for example:
2085
2086 open FOO || die;
2087
2088It may also indicate a misspelled constant that has been interpreted
2089as a bareword:
2090
2091 use constant TYPO => 1;
2092 if (TYOP) { print "foo" }
2093
2094The C<strict> pragma is useful in avoiding such errors.
2095
a99ba403
GS
2096=item Binary number > 0b11111111111111111111111111111111 non-portable
2097
2098(W) The binary number you specified is larger than 2**32-1
2099(4294967295) and therefore non-portable between systems. See
2100L<perlport> for more on portability concerns.
2101
2102=item Bit vector size > 32 non-portable
2103
2104(W) Using bit vector sizes larger than 32 is non-portable.
2105
2106=item Buffer overflow in prime_env_iter: %s
2107
2108(W) A warning peculiar to VMS. While Perl was preparing to iterate over
2109%ENV, it encountered a logical name or symbol definition which was too long,
2110so it was truncated to the string shown.
2111
2112=item Can't check filesystem of script "%s"
2113
2114(P) For some reason you can't check the filesystem of the script for nosuid.
2115
56e90b21
GS
2116=item Can't declare class for non-scalar %s in "%s"
2117
2118(S) Currently, only scalar variables can declared with a specific class
2119qualifier in a "my" or "our" declaration. The semantics may be extended
2120for other types of variables in future.
2121
2122=item Can't declare %s in "%s"
2123
2124(F) Only scalar, array, and hash variables may be declared as "my" or
2125"our" variables. They must have ordinary identifiers as names.
2126
0b5b802d
GS
2127=item Can't ignore signal CHLD, forcing to default
2128
2129(W) Perl has detected that it is being run with the SIGCHLD signal
2130(sometimes known as SIGCLD) disabled. Since disabling this signal
2131will interfere with proper determination of exit status of child
2132processes, Perl has reset the signal to its default value.
2133This situation typically indicates that the parent program under
2134which Perl may be running (e.g. cron) is being very careless.
2135
a99ba403
GS
2136=item Can't modify non-lvalue subroutine call
2137
437784d6
GS
2138(F) Subroutines meant to be used in lvalue context should be declared as
2139such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
2140
2141=item Can't read CRTL environ
2142
2143(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2144from the CRTL's internal environment array and discovered the array was
2145missing. You need to figure out where your CRTL misplaced its environ
2146or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2147
2148=item Can't remove %s: %s, skipping file
2149
2150(S) You requested an inplace edit without creating a backup file. Perl
2151was unable to remove the original file to replace it with the modified
2152file. The file was left unmodified.
2153
2154=item Can't return %s from lvalue subroutine
2155
2156(F) Perl detected an attempt to return illegal lvalues (such
2157as temporary or readonly values) from a subroutine used as an lvalue.
2158This is not allowed.
2159
2160=item Can't weaken a nonreference
2161
2162(F) You attempted to weaken something that was not a reference. Only
2163references can be weakened.
2164
2165=item Character class [:%s:] unknown
2166
2167(F) The class in the character class [: :] syntax is unknown.
437784d6 2168See L<perlre>.
a99ba403
GS
2169
2170=item Character class syntax [%s] belongs inside character classes
2171
2172(W) The character class constructs [: :], [= =], and [. .] go
2173I<inside> character classes, the [] are part of the construct,
437784d6
GS
2174for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2175are not currently implemented; they are simply placeholders for
2176future extensions.
a99ba403
GS
2177
2178=item Constant is not %s reference
2179
2180(F) A constant value (perhaps declared using the C<use constant> pragma)
2181is being dereferenced, but it amounts to the wrong type of reference. The
2182message indicates the type of reference that was expected. This usually
2183indicates a syntax error in dereferencing the constant value.
2184See L<perlsub/"Constant Functions"> and L<constant>.
2185
2186=item constant(%s): %%^H is not localized
2187
2188(F) When setting compile-time-lexicalized hash %^H one should set the
2189corresponding bit of $^H as well.
2190
2191=item constant(%s): %s
2192
2193(F) Compile-time-substitutions (such as overloaded constants and
2194character names) were not correctly set up.
2195
2196=item defined(@array) is deprecated
2197
2198(D) defined() is not usually useful on arrays because it checks for an
2199undefined I<scalar> value. If you want to see if the array is empty,
2200just use C<if (@array) { # not empty }> for example.
2201
2202=item defined(%hash) is deprecated
2203
2204(D) defined() is not usually useful on hashes because it checks for an
2205undefined I<scalar> value. If you want to see if the hash is empty,
2206just use C<if (%hash) { # not empty }> for example.
2207
2208=item Did not produce a valid header
2209
2210See Server error.
2211
33633739
GS
2212=item Did you mean "local" instead of "our"?
2213
2214(W) Remember that "our" does not localize the declared global variable.
2215You have declared it again in the same lexical scope, which seems superfluous.
2216
a99ba403
GS
2217=item Document contains no data
2218
2219See Server error.
2220
2221=item entering effective %s failed
2222
2223(F) While under the C<use filetest> pragma, switching the real and
2224effective uids or gids failed.
6b121555 2225
73b437c8
JH
2226=item false [] range "%s" in regexp
2227
2228(W) A character class range must start and end at a literal character, not
2229another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2230range is interpreted as a literal "-". Consider quoting the "-", "\-".
2231See L<perlre>.
2232
af8c498a 2233=item Filehandle %s opened only for output
6b121555 2234
af8c498a 2235(W) You tried to read from a filehandle opened only for writing. If you
437784d6 2236intended it to be a read/write filehandle, you needed to open it with
c47ff5f1
GS
2237"+<" or "+>" or "+>>" instead of with "<" or nothing. If
2238you intended only to read from the file, use "<". See
af8c498a 2239L<perlfunc/open>.
e02fdbd2 2240
56e90b21
GS
2241=item flock() on closed filehandle %s
2242
2243(W) The filehandle you're attempting to flock() got itself closed some
2244time before now. Check your logic flow. flock() operates on filehandles.
2245Are you attempting to call flock() on a dirhandle by the same name?
2246
2247=item Global symbol "%s" requires explicit package name
2248
2249(F) You've said "use strict vars", which indicates that all variables
2250must either be lexically scoped (using "my"), declared beforehand using
2251"our", or explicitly qualified to say which package the global variable
2252is in (using "::").
2253
a99ba403
GS
2254=item Hexadecimal number > 0xffffffff non-portable
2255
2256(W) The hexadecimal number you specified is larger than 2**32-1
2257(4294967295) and therefore non-portable between systems. See
2258L<perlport> for more on portability concerns.
2259
2260=item Ill-formed CRTL environ value "%s"
2261
2262(W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2263environ array, and encountered an element without the C<=> delimiter
2264used to spearate keys from values. The element is ignored.
2265
2266=item Ill-formed message in prime_env_iter: |%s|
2267
2268(W) A warning peculiar to VMS. Perl tried to read a logical name
2269or CLI symbol definition when preparing to iterate over %ENV, and
2270didn't see the expected delimiter between key and value, so the
2271line was ignored.
2272
2273=item Illegal binary digit %s
2274
437784d6 2275(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
2276
2277=item Illegal binary digit %s ignored
2278
2279(W) You may have tried to use a digit other than 0 or 1 in a binary number.
2280Interpretation of the binary number stopped before the offending digit.
2281
2282=item Illegal number of bits in vec
2283
2284(F) The number of bits in vec() (the third argument) must be a power of
2285two from 1 to 32 (or 64, if your platform supports that).
2286
2287=item Integer overflow in %s number
2288
2289(W) The hexadecimal, octal or binary number you have specified either
c6edd1b7 2290as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
2291architecture, and has been converted to a floating point number. On a
229232-bit architecture the largest hexadecimal, octal or binary number
2293representable without overflow is 0xFFFFFFFF, 037777777777, or
22940b11111111111111111111111111111111 respectively. Note that Perl
2295transparently promotes all numbers to a floating point representation
2296internally--subject to loss of precision errors in subsequent
2297operations.
2298
09bef843
SB
2299=item Invalid %s attribute: %s
2300
2301The indicated attribute for a subroutine or variable was not recognized
2302by Perl or by a user-supplied handler. See L<attributes>.
2303
2304=item Invalid %s attributes: %s
2305
2306The indicated attributes for a subroutine or variable were not recognized
2307by Perl or by a user-supplied handler. See L<attributes>.
2308
73b437c8
JH
2309=item invalid [] range "%s" in regexp
2310
2311The offending range is now explicitly displayed.
2312
09bef843
SB
2313=item Invalid separator character %s in attribute list
2314
0120eecf 2315(F) Something other than a colon or whitespace was seen between the
09bef843
SB
2316elements of an attribute list. If the previous attribute
2317had a parenthesised parameter list, perhaps that list was terminated
2318too soon. See L<attributes>.
2319
a99ba403
GS
2320=item Invalid separator character %s in subroutine attribute list
2321
0120eecf 2322(F) Something other than a colon or whitespace was seen between the
a99ba403
GS
2323elements of a subroutine attribute list. If the previous attribute
2324had a parenthesised parameter list, perhaps that list was terminated
2325too soon.
2326
2327=item leaving effective %s failed
2328
2329(F) While under the C<use filetest> pragma, switching the real and
2330effective uids or gids failed.
2331
2332=item Lvalue subs returning %s not implemented yet
2333
2334(F) Due to limitations in the current implementation, array and hash
2335values cannot be returned in subroutines used in lvalue context.
2336See L<perlsub/"Lvalue subroutines">.
2337
2338=item Method %s not permitted
2339
2340See Server error.
2341
2342=item Missing %sbrace%s on \N{}
2343
2344(F) Wrong syntax of character name literal C<\N{charname}> within
2345double-quotish context.
2346
06eaf0bc
GS
2347=item Missing command in piped open
2348
2349(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2350construction, but the command was missing or blank.
2351
09bef843
SB
2352=item Missing name in "my sub"
2353
2354(F) The reserved syntax for lexically scoped subroutines requires that they
2355have a name with which they can be found.
2356
56e90b21
GS
2357=item No %s specified for -%c
2358
2359(F) The indicated command line switch needs a mandatory argument, but
2360you haven't specified one.
2361
2362=item No package name allowed for variable %s in "our"
2363
2364(F) Fully qualified variable names are not allowed in "our" declarations,
2365because that doesn't make much sense under existing semantics. Such
2366syntax is reserved for future extensions.
2367
2368=item No space allowed after -%c
2369
2370(F) The argument to the indicated command line switch must follow immediately
2371after the switch, without intervening spaces.
2372
a99ba403
GS
2373=item no UTC offset information; assuming local time is UTC
2374
2375(S) A warning peculiar to VMS. Perl was unable to find the local
2376timezone offset, so it's assuming that local system time is equivalent
2377to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2378to translate to the number of seconds which need to be added to UTC to
2379get local time.
2380
2381=item Octal number > 037777777777 non-portable
2382
2383(W) The octal number you specified is larger than 2**32-1 (4294967295)
2384and therefore non-portable between systems. See L<perlport> for more
2385on portability concerns.
2386
2387See also L<perlport> for writing portable code.
2388
2389=item panic: del_backref
2390
2391(P) Failed an internal consistency check while trying to reset a weak
2392reference.
2393
2394=item panic: kid popen errno read
2395
2396(F) forked child returned an incomprehensible message about its errno.
2397
2398=item panic: magic_killbackrefs
2399
2400(P) Failed an internal consistency check while trying to reset all weak
2401references to an object.
2402
56e90b21
GS
2403=item Parentheses missing around "%s" list
2404
2405(W) You said something like
2406
2407 my $foo, $bar = @_;
2408
2409when you meant
2410
2411 my ($foo, $bar) = @_;
2412
54884818 2413Remember that "my", "our", and "local" bind tighter than comma.
56e90b21 2414
a99ba403
GS
2415=item Possible Y2K bug: %s
2416
2417(W) You are concatenating the number 19 with another number, which
2418could be a potential Year 2000 problem.
2419
2420=item Premature end of script headers
2421
2422See Server error.
2423
0b5b802d
GS
2424=item Repeat count in pack overflows
2425
2426(F) You can't specify a repeat count so large that it overflows
2427your signed integers. See L<perlfunc/pack>.
2428
2429=item Repeat count in unpack overflows
2430
2431(F) You can't specify a repeat count so large that it overflows
2432your signed integers. See L<perlfunc/unpack>.
2433
a99ba403
GS
2434=item realloc() of freed memory ignored
2435
2436(S) An internal routine called realloc() on something that had already
2437been freed.
2438
2439=item Reference is already weak
2440
2441(W) You have attempted to weaken a reference that is already weak.
2442Doing so has no effect.
2443
2444=item setpgrp can't take arguments
2445
2446(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2447unlike POSIX setpgid(), which takes a process ID and process group ID.
2448
2449=item Strange *+?{} on zero-length expression
2450
2451(W) You applied a regular expression quantifier in a place where it
2452makes no sense, such as on a zero-width assertion.
2453Try putting the quantifier inside the assertion instead. For example,
2454the way to match "abc" provided that it is followed by three
2455repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2456
2457=item switching effective %s is not implemented
2458
2459(F) While under the C<use filetest> pragma, we cannot switch the
2460real and effective uids or gids.
2461
437784d6 2462=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
2463
2464=item This Perl can't set CRTL environ elements (%s=%s)
2465
2466(W) Warnings peculiar to VMS. You tried to change or delete an element
2467of the CRTL's internal environ array, but your copy of Perl wasn't
2468built with a CRTL that contained the setenv() function. You'll need to
2469rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2470L<perlvms>) so that the environ array isn't the target of the change to
2471%ENV which produced the warning.
2472
2473=item Unknown open() mode '%s'
2474
437784d6 2475(F) The second argument of 3-argument open() is not among the list
c47ff5f1
GS
2476of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2477C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
a99ba403
GS
2478
2479=item Unknown process %x sent message to prime_env_iter: %s
2480
2481(P) An error peculiar to VMS. Perl was reading values for %ENV before
2482iterating over it, and someone else stuck a message in the stream of
2483data Perl expected. Someone's very confused, or perhaps trying to
2484subvert Perl's population of %ENV for nefarious purposes.
2485
af8c498a
GS
2486=item Unrecognized escape \\%c passed through
2487
2488(W) You used a backslash-character combination which is not recognized
1028017a 2489by Perl. The character was understood literally.
af8c498a 2490
09bef843
SB
2491=item Unterminated attribute parameter in attribute list
2492
2493(F) The lexer saw an opening (left) parenthesis character while parsing an
2494attribute list, but the matching closing (right) parenthesis
2495character was not found. You may need to add (or remove) a backslash
2496character to get your parentheses to balance. See L<attributes>.
2497
2498=item Unterminated attribute list
2499
2500(F) The lexer found something other than a simple identifier at the start
2501of an attribute, and it wasn't a semicolon or the start of a
2502block. Perhaps you terminated the parameter list of the previous attribute
2503too soon. See L<attributes>.
2504
09bef843
SB
2505=item Unterminated attribute parameter in subroutine attribute list
2506
2507(F) The lexer saw an opening (left) parenthesis character while parsing a
2508subroutine attribute list, but the matching closing (right) parenthesis
2509character was not found. You may need to add (or remove) a backslash
2510character to get your parentheses to balance.
2511
2512=item Unterminated subroutine attribute list
2513
2514(F) The lexer found something other than a simple identifier at the start
2515of a subroutine attribute, and it wasn't a semicolon or the start of a
2516block. Perhaps you terminated the parameter list of the previous attribute
2517too soon.
2518
a99ba403 2519=item Value of CLI symbol "%s" too long
eb6e2d6f 2520
a99ba403
GS
2521(W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2522element from a CLI symbol table, and found a resultant string longer
2523than 1024 characters. The return value has been truncated to 1024
2524characters.
eb6e2d6f 2525
a99ba403 2526=item Version number must be a constant number
ba8251e8 2527
a99ba403
GS
2528(P) The attempt to translate a C<use Module n.n LIST> statement into
2529its equivalent C<BEGIN> block found an internal inconsistency with
2530the version number.
2531
2532=back
27806c82 2533
a5222a85 2534=head1 Obsolete Diagnostics
3175b8cd 2535
a99ba403
GS
2536=over 4
2537
2538=item Character class syntax [: :] is reserved for future extensions
2539
2540(W) Within regular expression character classes ([]) the syntax beginning
2541with "[:" and ending with ":]" is reserved for future extensions.
2542If you need to represent those character sequences inside a regular
2543expression character class, just quote the square brackets with the
2544backslash: "\[:" and ":\]".
2545
2546=item Ill-formed logical name |%s| in prime_env_iter
2547
2548(W) A warning peculiar to VMS. A logical name was encountered when preparing
2549to iterate over %ENV which violates the syntactic rules governing logical
2550names. Because it cannot be translated normally, it is skipped, and will not
2551appear in %ENV. This may be a benign occurrence, as some software packages
2552might directly modify logical name tables and introduce nonstandard names,
2553or it may indicate that a logical name table has been corrupted.
2554
34d09196
GS
2555=item Probable precedence problem on %s
2556
2557(W) The compiler found a bareword where it expected a conditional,
2558which often indicates that an || or && was parsed as part of the
2559last argument of the previous construct, for example:
2560
2561 open FOO || die;
2562
a99ba403
GS
2563=item regexp too big
2564
2565(F) The current implementation of regular expressions uses shorts as
2566address offsets within a string. Unfortunately this means that if
2567the regular expression compiles to longer than 32767, it'll blow up.
2568Usually when you want a regular expression this big, there is a better
2569way to do it with multiple statements. See L<perlre>.
2570
2571=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2572
2573(D) Perl versions before 5.004 misinterpreted any type marker followed
2574by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2575"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2576
2577However, the developers of Perl 5.004 could not fix this bug completely,
2578because at least two widely-used modules depend on the old meaning of
2579"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2580old (broken) way inside strings; but it generates this message as a
2581warning. And in Perl 5.005, this special treatment will cease.
2582
2583=back
3175b8cd 2584
ba8251e8
GS
2585=head1 BUGS
2586
437784d6 2587If you find what you think is a bug, you might check the
14218588 2588articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
GS
2589There may also be information at http://www.perl.com/perl/, the Perl
2590Home Page.
2591
2592If you believe you have an unreported bug, please run the B<perlbug>
14218588 2593program included with your release. Make sure to trim your bug down
ba8251e8 2594to a tiny but sufficient test case. Your bug report, along with the
14218588 2595output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
GS
2596analysed by the Perl porting team.
2597
2598=head1 SEE ALSO
2599
2600The F<Changes> file for exhaustive details on what changed.
2601
2602The F<INSTALL> file for how to build Perl.
2603
2604The F<README> file for general stuff.
2605
2606The F<Artistic> and F<Copying> files for copyright information.
2607
2608=head1 HISTORY
2609
a5222a85
GS
2610Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2611contributions from The Perl Porters.
ba8251e8
GS
2612
2613Send omissions or corrections to <F<perlbug@perl.com>>.
2614
2615=cut