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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<$$ . "1">,
133but still allowed it.
134
21bad921 135In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
a5222a85 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
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200configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
201be warned that the semantics of all the bitwise numeric operators
202(& | ^ ~ << >>) have been changed. These operators used to strictly
203operate on the lower 32 bits of integers, but now operate over the
204entire width of native integers. In particular, note that unary C<~>
205will produce different results on platforms that have different
206$Config{ivsize}. For portability, be sure to mask off the excess bits
207in the result of unary C<~>, e.g., C<~$x & 0xffffffff>.
34b59bff 208
227e8dd4 209=head2 More builtins taint their results
4602f195 210
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211The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(),
212and getpwuid() are now tainted, because the user can affect their own
213encrypted password and login shell.
4602f195 214
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215The variable modified by shmread(), and messages returned by msgrcv()
216(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
217because other untrusted processes can modify messages and shared memory
218segments for their own nefarious purposes.
d929ce6f 219
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220To avoid these new tainting behaviors, you can build Perl with the
221Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the
222ensuing perl binary may be insecure.
d929ce6f 223
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224=back
225
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226=head2 C Source Incompatibilities
227
228=over 4
229
230=item C<PERL_POLLUTE>
231
232Release 5.005 grandfathered old global symbol names by providing preprocessor
642f9deb 233macros for extension source compatibility. As of release 5.6.0, these
e02fdbd2 234preprocessor definitions are not available by default. You need to explicitly
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235compile perl with C<-DPERL_POLLUTE> to get these definitions. For
236extensions still using the old symbols, this option can be
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237specified via MakeMaker:
238
14218588 239 perl Makefile.PL POLLUTE=1
e02fdbd2 240
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241=item C<PERL_IMPLICIT_CONTEXT>
242
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243 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
244 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
245 intended to be enabled by users at this time.
af365420 246
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247This new build option provides a set of macros for all API functions
248such that an implicit interpreter/thread context argument is passed to
249every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 250amounts to a macro invocation that actually translates to something like
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251C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
252to not have any significant source compatibility issues, the difference
253between a macro and a real function call will need to be considered.
254
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255This means that there B<is> a source compatibility issue as a result of
256this if your extensions attempt to use pointers to any of the Perl API
257functions.
258
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259Note that the above issue is not relevant to the default build of
260Perl, whose interfaces continue to match those of prior versions
261(but subject to the other options described here).
262
2c2d71f5 263See L<perlguts/"The Perl API"> for detailed information on the
642f9deb 264ramifications of building Perl with this option.
2c2d71f5 265
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266=item C<PERL_POLLUTE_MALLOC>
267
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268Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
269the system's malloc family of functions to be usurped by the Perl versions,
270since by default they used the same names. Besides causing problems on
271platforms that do not allow these functions to be cleanly replaced, this
272also meant that the system versions could not be called in programs that
273used Perl's malloc. Previous versions of Perl have allowed this behaviour
274to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
275definitions.
86058a2d 276
642f9deb 277As of release 5.6.0, Perl's malloc family of functions have default names
86058a2d 278distinct from the system versions. You need to explicitly compile perl with
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279C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
280and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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281the default.
282
283Note that these functions do B<not> constitute Perl's memory allocation API.
284See L<perlguts/"Memory Allocation"> for further information about that.
285
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286=back
287
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288=head2 Compatible C Source API Changes
289
290=over
291
292=item C<PATCHLEVEL> is now C<PERL_VERSION>
293
14218588 294The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 295are now available by default from perl.h, and reflect the base revision,
14218588 296patchlevel, and subversion respectively. C<PERL_REVISION> had no
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297prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
298previously available as C<PATCHLEVEL> and C<SUBVERSION>.
299
14218588 300The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 301the numbers have come to stand for in common practice. For compatibility,
14218588 302the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 303included (as required before), so there is no source incompatibility
14218588 304from the change.
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305
306=back
307
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308=head2 Binary Incompatibilities
309
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310In general, the default build of this release is expected to be binary
311compatible for extensions built with the 5.005 release or its maintenance
312versions. However, specific platforms may have broken binary compatibility
313due to changes in the defaults used in hints files. Therefore, please be
314sure to always check the platform-specific README files for any notes to
315the contrary.
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316
317The usethreads or usemultiplicity builds are B<not> binary compatible
318with the corresponding builds in 5.005.
e02fdbd2 319
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320On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
321among others), purely internal symbols such as parser functions and the
322run time opcodes are not exported by default. Perl 5.005 used to export
323all functions irrespective of whether they were considered part of the
324public API or not.
325
326For the full list of public API functions, see L<perlapi>.
327
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328=head1 Installation and Configuration Improvements
329
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330=head2 -Dusethreads means something different
331
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332 WARNING: Support for threads continues to be an experimental feature.
333 Interfaces and implementation are subject to sudden and drastic changes.
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334
335The -Dusethreads flag now enables the experimental interpreter-based thread
336support by default. To get the flavor of experimental threads that was in
ba869deb 3375.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
16070b82 338
642f9deb 339As of v5.6.0, interpreter-threads support is still lacking a way to
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340create new threads from Perl (i.e., C<use Thread;> will not work with
341interpreter threads). C<use Thread;> continues to be available when you
642f9deb 342specify the -Duse5005threads option to Configure, bugs and all.
16070b82 343
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344=head2 New Configure flags
345
346The following new flags may be enabled on the Configure command line
347by running Configure with C<-Dflag>.
348
349 usemultiplicity
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350 usethreads useithreads (new interpreter threads: no Perl API yet)
351 usethreads use5005threads (threads as they were in 5.005)
67d3893f 352
ba869deb 353 use64bitint (equal to now deprecated 'use64bits')
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354 use64bitall
355
67d3893f 356 uselongdouble
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357 usemorebits
358 uselargefiles
ba869deb 359 usesocks (only SOCKS v5 supported)
a5222a85 360
10cc9d2a 361=head2 Threadedness and 64-bitness now more daring
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362
363The Configure options enabling the use of threads and the use of
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36464-bitness are now more daring in the sense that they no more have an
365explicit list of operating systems of known threads/64-bit
67d3893f 366capabilities. In other words: if your operating system has the
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367necessary APIs and datatypes, you should be able just to go ahead and
368use them, for threads by Configure -Dusethreads, and for 64 bits
10cc9d2a 369either explicitly by Configure -Duse64bitint or implicitly if your
642f9deb 370system has 64-bit wide datatypes. See also L<"64-bit support">.
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371
372=head2 Long Doubles
373
374Some platforms have "long doubles", floating point numbers of even
437784d6 375larger range than ordinary "doubles". To enable using long doubles for
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376Perl's scalars, use -Duselongdouble.
377
378=head2 -Dusemorebits
379
642f9deb 380You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
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381See also L<"64-bit support">.
382
383=head2 -Duselargefiles
384
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385Some platforms support system APIs that are capable of handling large files
386(typically, files larger than two gigabytes). Perl will try to use these
387APIs if you ask for -Duselargefiles.
388
67d3893f 389See L<"Large file support"> for more information.
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390
391=head2 installusrbinperl
392
393You can use "Configure -Uinstallusrbinperl" which causes installperl
394to skip installing perl also as /usr/bin/perl. This is useful if you
395prefer not to modify /usr/bin for some reason or another but harmful
396because many scripts assume to find Perl in /usr/bin/perl.
397
398=head2 SOCKS support
399
400You can use "Configure -Dusesocks" which causes Perl to probe
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401for the SOCKS proxy protocol library (v5, not v4). For more information
402on SOCKS, see:
403
404 http://www.socks.nec.com/
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405
406=head2 C<-A> flag
407
408You can "post-edit" the Configure variables using the Configure C<-A>
642f9deb 409switch. The editing happens immediately after the platform specific
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410hints files have been processed but before the actual configuration
411process starts. Run C<Configure -h> to find out the full C<-A> syntax.
412
c35dd67d 413=head2 Enhanced Installation Directories
67d3893f 414
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415The installation structure has been enriched to improve the support
416for maintaining multiple versions of perl, to provide locations for
417vendor-supplied modules, scripts, and manpages, and to ease maintenance
418of locally-added modules, scripts, and manpages. See the section on
419Installation Directories in the INSTALL file for complete details.
420For most users building and installing from source, the defaults should
421be fine.
422
423If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
424special values for library directories, you might wish to consider using
425the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
426config.sh file from an earlier version of perl, you should be sure to
427check that Configure makes sensible choices for the new directories.
428See INSTALL for complete details.
67d3893f 429
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430=head1 Core Changes
431
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432=head2 Unicode and UTF-8 support
433
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434 WARNING: This is an experimental feature. Implementation details are
435 subject to change.
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436
437Perl now uses UTF-8 as its internal representation for character
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438strings. The C<utf8> and C<bytes> pragmas are used to control this support
439in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
393fec97 440more information.
9d73390d 441
16070b82 442=head2 Interpreter cloning, threads, and concurrency
af365420 443
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444 WARNING: This is an experimental feature. Implementation details are
445 subject to change.
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446
447Perl 5.005_63 introduces the beginnings of support for running multiple
448interpreters concurrently in different threads. In conjunction with
449the perl_clone() API call, which can be used to selectively duplicate
450the state of any given interpreter, it is possible to compile a
451piece of code once in an interpreter, clone that interpreter
452one or more times, and run all the resulting interpreters in distinct
453threads.
454
455On Windows, this feature is used to emulate fork() at the interpreter
456level. See L<perlfork>.
457
458This feature is still in evolution. It is eventually meant to be used
459to selectively clone a subroutine and data reachable from that
460subroutine in a separate interpreter and run the cloned subroutine
461in a separate thread. Since there is no shared data between the
462interpreters, little or no locking will be needed (unless parts of
463the symbol table are explicitly shared). This is obviously intended
464to be an easy-to-use replacement for the existing threads support.
465
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466Support for cloning interpreters and interpreter concurrency can be
467enabled using the -Dusethreads Configure option (see win32/Makefile for
468how to enable it on Windows.) The resulting perl executable will be
469functionally identical to one that was built with -Dmultiplicity, but
470the perl_clone() API call will only be available in the former.
af365420 471
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472-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
473enables Perl source code changes that provide a clear separation between
474the op tree and the data it operates with. The former is immutable, and
475can therefore be shared between an interpreter and all of its clones,
476while the latter is considered local to each interpreter, and is therefore
477copied for each clone.
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478
479Note that building Perl with the -Dusemultiplicity Configure option
480is adequate if you wish to run multiple B<independent> interpreters
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481concurrently in different threads. -Dusethreads only provides the
482additional functionality of the perl_clone() API call and other
483support for running B<cloned> interpreters concurrently.
af365420 484
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485=head2 Lexically scoped warning categories
486
487You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 488level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 489for details.
9d73390d 490
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491=head2 Lvalue subroutines
492
642f9deb 493 WARNING: This is an experimental feature. Details are subject to change.
a5222a85 494
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495Subroutines can now return modifiable lvalues.
496See L<perlsub/"Lvalue subroutines">.
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497
498=head2 "our" declarations
499
500An "our" declaration introduces a value that can be best understood
501as a lexically scoped symbolic alias to a global variable in the
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502package that was current where the variable was declared. This is
503mostly useful as an alternative to the C<vars> pragma, but also provides
504the opportunity to introduce typing and other attributes for such
505variables. See L<perlfunc/our>.
506
44dcb63b 507=head2 Support for strings represented as a vector of ordinals
16070b82 508
dd629d5b 509Literals of the form C<v1.2.3.4> are now parsed as a string composed of
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510of characters with the specified ordinals. This is an alternative, more
511readable way to construct (possibly unicode) strings instead of
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512interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
513C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
514parsed the same as C<v1.2.3>.
16070b82 515
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516Strings written in this form are also useful to represent version "numbers".
517It is easy to compare such version "numbers" (which are really just plain
518strings) using any of the usual string comparison operators C<eq>, C<ne>,
519C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
520C<&>, etc.
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521
522In conjunction with the new C<$^V> magic variable (which contains
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523the perl version as a string), such literals can be used as a readable way
524to check if you're running a particular version of Perl:
16070b82 525
44dcb63b 526 # this will parse in older versions of Perl also
642f9deb 527 if ($^V and $^V gt v5.6.0) {
44dcb63b 528 # new features supported
16070b82
GS
529 }
530
44dcb63b
GS
531C<require> and C<use> also have some special magic to support such literals.
532They will be interpreted as a version rather than as a module name:
16070b82 533
b22c7a20
GS
534 require v5.6.0; # croak if $^V lt v5.6.0
535 use v5.6.0; # same, but croaks at compile-time
a5222a85 536
dd629d5b
GS
537Alternatively, the C<v> may be omitted if there is more than one dot:
538
539 require 5.6.0;
540 use 5.6.0;
541
44dcb63b 542Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
b22c7a20 543to print ordinals of characters in arbitrary strings:
1761cee5 544
b22c7a20
GS
545 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
546 printf "%*vX", ":", $addr; # formats IPv6 address
dd629d5b 547 printf "%*vb", " ", $bits; # displays bitstring
1761cee5 548
191d61a7 549See L<perldata/"Scalar value constructors"> for additional information.
44dcb63b 550
a5222a85
GS
551=head2 Weak references
552
fc641c2d 553 WARNING: This is an experimental feature. Details are subject to change.
a5222a85 554
d4629d6a
GS
555In previous versions of Perl, you couldn't cache objects so as
556to allow them to be deleted if the last reference from outside
557the cache is deleted. The reference in the cache would hold a
558reference count on the object and the objects would never be
559destroyed.
560
561Another familiar problem is with circular references. When an
562object references itself, its reference count would never go
563down to zero, and it would not get destroyed until the program
564is about to exit.
565
566Weak references solve this by allowing you to "weaken" any
567reference, that is, make it not count towards the reference count.
568When the last non-weak reference to an object is deleted, the object
569is destroyed and all the weak references to the object are
570automatically undef-ed.
a5222a85 571
d4629d6a
GS
572To use this feature, you need the WeakRef package from CPAN, which
573contains additional documentation.
574
becf2bd3
GS
575=head2 File globbing implemented internally
576
642f9deb
GS
577 WARNING: This is currently an experimental feature. Interfaces and
578 implementation are likely to change.
becf2bd3 579
52bb0670
GS
580Perl now uses the File::Glob implementation of the glob() operator
581automatically. This avoids using an external csh process and the
582problems associated with it.
becf2bd3 583
5fdc711f
GS
584=head2 Binary numbers supported
585
4f19785b
WSI
586Binary numbers are now supported as literals, in s?printf formats, and
587C<oct()>:
588
14218588
GS
589 $answer = 0b101010;
590 printf "The answer is: %b\n", oct("0b101010");
4f19785b 591
a5222a85
GS
592=head2 Some arrows may be omitted in calls through references
593
594Perl now allows the arrow to be omitted in many constructs
595involving subroutine calls through references. For example,
c47ff5f1 596C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
a5222a85 597This is rather similar to how the arrow may be omitted from
c47ff5f1
GS
598C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
599required for C<< foo(10)->('bar') >>.
a5222a85 600
afebc493
GS
601=head2 exists() is supported on subroutine names
602
603The exists() builtin now works on subroutine names. A subroutine
604is considered to exist if it has been declared (even if implicitly).
605See L<perlfunc/exists> for examples.
606
01020589
GS
607=head2 exists() and delete() are supported on array elements
608
609The exists() and delete() builtins now work on simple arrays as well.
610The behavior is similar to that on hash elements.
611
8ea97a1e 612exists() can be used to check whether an array element has been
8216c1fd
GS
613initialized. This avoids autovivifying array elements that don't exist.
614If the array is tied, the EXISTS() method in the corresponding tied
615package will be invoked.
8ea97a1e
GS
616
617delete() may be used to remove an element from the array and return
618it. The array element at that position returns to its unintialized
619state, so that testing for the same element with exists() will return
620false. If the element happens to be the one at the end, the size of
8216c1fd
GS
621the array also shrinks up to the highest element that tests true for
622exists(), or 0 if none such is found. If the array is tied, the DELETE()
623method in the corresponding tied package will be invoked.
01020589
GS
624
625See L<perlfunc/exists> and L<perlfunc/delete> for examples.
626
5fdc711f
GS
627=head2 syswrite() ease-of-use
628
a5222a85
GS
629The length argument of C<syswrite()> has become optional.
630
b1a9ed4a 631=head2 File and directory handles can be autovivified
a5222a85 632
c47ff5f1 633Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
b1a9ed4a
GS
634handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
635socket(), and accept()) now autovivify a file or directory handle
636if the handle passed to them is an uninitialized scalar variable. This
637allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
638to be used to create filehandles that will conveniently be closed
639automatically when the scope ends, provided there are no other references
640to them. This largely eliminates the need for typeglobs when opening
641filehandles that must be passed around, as in the following example:
a5222a85
GS
642
643 sub myopen {
644 open my $fh, "@_"
645 or die "Can't open '@_': $!";
646 return $fh;
647 }
648
649 {
650 my $f = myopen("</etc/motd");
651 print <$f>;
652 # $f implicitly closed here
653 }
654
642f9deb
GS
655=head2 open() with more than two arguments
656
657If open() is passed three arguments instead of two, the second arguments
658is used as the mode and the third argument is taken to be the file name.
659This is primarily useful for protecting against unintended magic behavior
660of the traditional two-argument form. See L<perlfunc/open>.
6c67e1bb 661
5fdc711f
GS
662=head2 64-bit support
663
642f9deb
GS
664 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
665 deprecated. Use -Duse64bitint instead.
10cc9d2a 666
55f6b6ec
JH
667Any platform that has 64-bit integers either
668
669 (1) natively as longs or ints
670 (2) via special compiler flags
671 (3) using long long or int64_t
672
673are able to use "quads" (64-bit integers) as follows:
9c107f78
JH
674
675=over 4
676
a5222a85
GS
677=item *
678
679constants (decimal, hexadecimal, octal, binary) in the code
680
681=item *
9c107f78 682
a5222a85 683arguments to oct() and hex()
9c107f78 684
a5222a85
GS
685=item *
686
687arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
688
689=item *
9c107f78 690
a5222a85 691printed as such
9c107f78 692
a5222a85
GS
693=item *
694
695pack() and unpack() "q" and "Q" formats
696
697=item *
698
972b05a9
JH
699in basic arithmetics: + - * / % (NOTE: operating close to the limits
700of the integer values may produce surprising results)
a5222a85
GS
701
702=item *
1fad5d67 703
972b05a9 704in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
642f9deb 705to be 32 bits wide but now operate on the full native width.)
972b05a9
JH
706
707=item *
708
709vec()
9c107f78
JH
710
711=back
712
713Note that unless you have the case (a) you will have to configure
10cc9d2a 714and compile Perl using the -Duse64bitint Configure flag.
9c107f78 715
49c10eea 716There are actually two modes of 64-bitness: the first one is achieved
10cc9d2a
JH
717using Configure -Duse64bitint and the second one using Configure
718-Duse64bitall. The difference is that the first one is minimal and
55f6b6ec
JH
719the second one maximal.
720
721The C<use64bitint> does only as much as is required to get 64-bit
722integers into Perl (this may mean, for example, using "long longs")
723while your memory may still be limited to 2 gigabytes (because your
724pointers could still be 32-bit). Note that the name C<64bitint> does
725not imply that your C compiler will be using 64-bit C<int>s (it might,
726but it doesn't have to): the C<use64bitint> means that you will be
727able to have 64 bits wide scalar values.
728
729The C<use64bitall> goes all the way by attempting to switch also
730integers (if it can), longs (and pointers) to being 64-bit. This may
731create an even more binary incompatible Perl than -Duse64bitint: the
732resulting executable may not run at all in a 32-bit box, or you may
733have to reboot/reconfigure/rebuild your operating system to be 64-bit
734aware.
49c10eea 735
10cc9d2a
JH
736Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
737nor -Duse64bitall.
49c10eea 738
2d4389e4 739Last but not least: note that due to Perl's habit of always using
07447971 740floating point numbers, the quads are still not true integers.
d0ba1bd2
JH
741When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
742-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
743are silently promoted to floating point numbers, after which they will
642f9deb 744start losing precision (in their lower digits).
2d4389e4
JH
745
746=head2 Large file support
747
748If you have filesystems that support "large files" (files larger than
aa855319 7492 gigabytes), you may now also be able to create and access them from
55f6b6ec
JH
750Perl. NOTE: the default action is to use the large file support, if
751available on the platform.
752
753If the large file support is on, and you have a Fcntl constant
754O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
755of sysopen().
756
757Beware: unless your filesystem also supports "sparse files" seeking to
758umpteen petabytes may be unadvisable.
2d4389e4 759
eed7fde4
JH
760Note that in addition to requiring a proper file system to do large
761files you may also need to adjust your per-process (or your
762per-system, or per-process-group, or per-user-group) maximum filesize
763limits before running Perl scripts that try to handle large files,
764especially if you intend to write such files.
765
766Finally, in addition to your process/process group maximum filesize
767limits, you may have quota limits on your filesystems that stop you
768(your user id or your user group id) from using large files.
769
770Adjusting your process/user/group/file system/operating system limits
771is outside the scope of Perl core language. For process limits, you
772may try increasing the limits using your shell's limits/limit/ulimit
773command before running Perl. The BSD::Resource extension (not
774included with the standard Perl distribution) may also be of use, it
775offers the getrlimit/setrlimit interface that can be used to adjust
776process resource usage limits, including the maximum filesize limit.
475d79b5 777
aa855319
JH
778=head2 Long doubles
779
780In some systems you may be able to use long doubles to enhance the
822ba51d 781range and precision of your double precision floating point numbers
aa855319
JH
782(that is, Perl's numbers). Use Configure -Duselongdouble to enable
783this support (if it is available).
784
785=head2 "more bits"
786
822ba51d 787You can "Configure -Dusemorebits" to turn on both the 64-bit support
aa855319 788and the long double support.
09bef843 789
43481408
GS
790=head2 Enhanced support for sort() subroutines
791
642f9deb 792Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
43481408 793now be used as sort subroutines. In either case, the two elements to
af365420 794be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
43481408
GS
795
796For unprototyped sort subroutines, the historical behavior of passing
797the elements to be compared as the global variables $a and $b remains
798unchanged.
799
62c18ce2
GS
800=head2 Better syntax checks on parenthesized unary operators
801
802Expressions such as:
803
14218588
GS
804 print defined(&foo,&bar,&baz);
805 print uc("foo","bar","baz");
806 undef($foo,&bar);
62c18ce2 807
7711098a 808used to be accidentally allowed in earlier versions, and produced
14218588
GS
809unpredictable behaviour. Some produced ancillary warnings
810when used in this way; others silently did the wrong thing.
62c18ce2
GS
811
812The parenthesized forms of most unary operators that expect a single
14218588
GS
813argument now ensure that they are not called with more than one
814argument, making the cases shown above syntax errors. The usual
815behaviour of:
62c18ce2 816
14218588
GS
817 print defined &foo, &bar, &baz;
818 print uc "foo", "bar", "baz";
819 undef $foo, &bar;
62c18ce2
GS
820
821remains unchanged. See L<perlop>.
822
3e3318e7
GS
823=head2 POSIX character class syntax [: :] supported
824
825For example to match alphabetic characters use /[[:alpha:]]/.
826See L<perlre> for details.
827
5a929a98 828=head2 Improved C<qw//> operator
8127e0e3 829
26ef7447
GS
830The C<qw//> operator is now evaluated at compile time into a true list
831instead of being replaced with a run time call to C<split()>. This
14218588
GS
832removes the confusing misbehaviour of C<qw//> in scalar context, which
833had inherited that behaviour from split().
26ef7447
GS
834
835Thus:
836
837 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
838
839now correctly prints "3|a", instead of "2|a".
8127e0e3 840
5a929a98
VU
841=head2 pack() format 'Z' supported
842
843The new format type 'Z' is useful for packing and unpacking null-terminated
844strings. See L<perlfunc/"pack">.
845
4d0c1c44 846=head2 pack() format modifier '!' supported
ee3907e2 847
14218588 848The new format type modifier '!' is useful for packing and unpacking
ee3907e2
JH
849native shorts, ints, and longs. See L<perlfunc/"pack">.
850
f29c64d6
GS
851=head2 pack() and unpack() support counted strings
852
a5222a85 853The template character '/' can be used to specify a counted string
f29c64d6
GS
854type to be packed or unpacked. See L<perlfunc/"pack">.
855
a5222a85
GS
856=head2 Comments in pack() templates
857
858The '#' character in a template introduces a comment up to
859end of the line. This facilitates documentation of pack()
860templates.
861
2b92dfce
GS
862=head2 $^X variables may now have names longer than one character
863
864Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
865error. Now variable names that begin with a control character may be
866arbitrarily long. However, for compatibility reasons, these variables
867I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 868C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
2b92dfce
GS
869than one control character, such as C<${^XY^Z}>, are illegal.
870
14218588
GS
871The old syntax has not changed. As before, `^X' may be either a
872literal control-X character or the two-character sequence `caret' plus
873`X'. When braces are omitted, the variable name stops after the
2b92dfce 874control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 875C<$^X . "YZ"> as before.
2b92dfce
GS
876
877As before, lexical variables may not have names beginning with control
878characters. As before, variables whose names begin with a control
14218588
GS
879character are always forced to be in package `main'. All such variables
880are reserved for future extensions, except those that begin with
09bef843 881C<^_>, which may be used by user programs and are guaranteed not to
14218588 882acquire special meaning in any future version of Perl.
2b92dfce 883
09bef843
SB
884=head2 C<use attrs> implicit in subroutine attributes
885
886Formerly, if you wanted to mark a subroutine as being a method call or
887as requiring an automatic lock() when it is entered, you had to declare
888that with a C<use attrs> pragma in the body of the subroutine.
16070b82 889That can now be accomplished with declaration syntax, like this:
09bef843 890
0120eecf 891 sub mymethod : locked method ;
09bef843 892 ...
16070b82
GS
893 sub mymethod : locked method {
894 ...
895 }
896
897 sub othermethod :locked :method ;
898 ...
899 sub othermethod :locked :method {
09bef843
SB
900 ...
901 }
902
16070b82
GS
903
904(Note how only the first C<:> is mandatory, and whitespace surrounding
905the C<:> is optional.)
906
09bef843
SB
907F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
908with the stubs they provide. See L<attributes>.
909
a5222a85
GS
910=head2 Support for interpolating named characters
911
21bad921
GS
912The new C<\N> escape interpolates named characters within strings.
913For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
914with a unicode smiley face at the end.
a5222a85 915
a5222a85
GS
916=head2 C<require> and C<do> may be overridden
917
918C<require> and C<do 'file'> operations may be overridden locally
919by importing subroutines of the same name into the current package
920(or globally by importing them into the CORE::GLOBAL:: namespace).
921Overriding C<require> will also affect C<use>, provided the override
922is visible at compile-time.
923See L<perlsub/"Overriding Built-in Functions">.
924
925=head2 New variable $^C reflects C<-c> switch
926
08cd8952 927C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
928in compile-only mode (i.e. via the C<-c> switch). Since
929BEGIN blocks are executed under such conditions, this variable
930enables perl code to determine whether actions that make sense
931only during normal running are warranted. See L<perlvar>.
932
063663a9 933=head2 New variable $^V contains Perl version as a string
16070b82 934
da2094fd 935C<$^V> contains the Perl version number as a string composed of
642f9deb 936characters whose ordinals match the version numbers, i.e. v5.6.0.
063663a9 937This may be used in string comparisons.
44dcb63b
GS
938
939See C<Support for strings represented as a vector of ordinals> for an
940example.
16070b82 941
a5222a85
GS
942=head2 Optional Y2K warnings
943
944If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
945it emits optional warnings when concatenating the number 19
946with another number.
947
948This behavior must be specifically enabled when running Configure.
b4bc034f 949See F<INSTALL> and F<README.Y2K>.
a5222a85 950
fbad3eb5
GS
951=head1 Significant bug fixes
952
c47ff5f1 953=head2 <HANDLE> on empty files
fbad3eb5 954
191f2cf3 955With C<$/> set to C<undef>, "slurping" an empty file returns a string of
14218588 956zero length (instead of C<undef>, as it used to) the first time the
191f2cf3
GS
957HANDLE is read after C<$/> is set to C<undef>. Further reads yield
958C<undef>.
fbad3eb5
GS
959
960This means that the following will append "foo" to an empty file (it used
14218588 961to do nothing):
fbad3eb5
GS
962
963 perl -0777 -pi -e 's/^/foo/' empty_file
964
14218588 965The behaviour of:
fbad3eb5
GS
966
967 perl -pi -e 's/^/foo/' empty_file
968
969is unchanged (it continues to leave the file empty).
970
0244c3a4
GS
971=head2 C<eval '...'> improvements
972
973Line numbers (as reflected by caller() and most diagnostics) within
642f9deb 974C<eval '...'> were often incorrect where here documents were involved.
0244c3a4
GS
975This has been corrected.
976
977Lexical lookups for variables appearing in C<eval '...'> within
978functions that were themselves called within an C<eval '...'> were
14218588
GS
979searching the wrong place for lexicals. The lexical search now
980correctly ends at the subroutine's block boundary.
0244c3a4
GS
981
982Parsing of here documents used to be flawed when they appeared as
983the replacement expression in C<eval 's/.../.../e'>. This has
984been fixed.
985
a5222a85
GS
986=head2 All compilation errors are true errors
987
988Some "errors" encountered at compile time were by neccessity
989generated as warnings followed by eventual termination of the
990program. This enabled more such errors to be reported in a
991single run, rather than causing a hard stop at the first error
992that was encountered.
993
994The mechanism for reporting such errors has been reimplemented
995to queue compile-time errors and report them at the end of the
996compilation as true errors rather than as warnings. This fixes
08cd8952
GS
997cases where error messages leaked through in the form of warnings
998when code was compiled at run time using C<eval STRING>, and
642f9deb 999also allows such errors to be reliably trapped using C<eval "...">.
a5222a85 1000
45bc9206
GS
1001=head2 Automatic flushing of output buffers
1002
14218588 1003fork(), exec(), system(), qx//, and pipe open()s now flush buffers
642f9deb
GS
1004of all files opened for output when the operation was attempted. This
1005mostly eliminates confusing buffering mishaps suffered by users unaware
1006of how Perl internally handles I/O.
45bc9206 1007
023ceb80
GS
1008This is not supported on some platforms like Solaris where a suitably
1009correct implementation of fflush(NULL) isn't available.
1010
af8c498a
GS
1011=head2 Better diagnostics on meaningless filehandle operations
1012
c47ff5f1 1013Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
af8c498a
GS
1014are compile time errors. Attempting to read from filehandles that
1015were opened only for writing will now produce warnings (just as
1016writing to read-only filehandles does).
1017
a5222a85
GS
1018=head2 Where possible, buffered data discarded from duped input filehandle
1019
c47ff5f1 1020C<< open(NEW, "<&OLD") >> now attempts to discard any data that
a5222a85
GS
1021was previously read and buffered in C<OLD> before duping the handle.
1022On platforms where doing this is allowed, the next read operation
1023on C<NEW> will return the same data as the corresponding operation
1024on C<OLD>. Formerly, it would have returned the data from the start
1025of the following disk block instead.
1026
820475bd
GS
1027=head2 eof() has the same old magic as <>
1028
c47ff5f1 1029C<eof()> would return true if no attempt to read from C<< <> >> had
820475bd 1030yet been made. C<eof()> has been changed to have a little magic of its
c47ff5f1 1031own, it now opens the C<< <> >> files.
820475bd 1032
a5222a85
GS
1033=head2 system(), backticks and pipe open now reflect exec() failure
1034
1035On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1036etc., are implemented via fork() and exec(). When the underlying
1037exec() fails, earlier versions did not report the error properly,
1038since the exec() happened to be in a different process.
1039
1040The child process now communicates with the parent about the
437784d6 1041error in launching the external command, which allows these
a5222a85
GS
1042constructs to return with their usual error value and set $!.
1043
1044=head2 Implicitly closed filehandles are safer
1045
1046Sometimes implicitly closed filehandles (as when they are localized,
1047and Perl automatically closes them on exiting the scope) could
1048inadvertently set $? or $!. This has been corrected.
1049
1050=head2 C<(\$)> prototype and C<$foo{a}>
1051
642f9deb 1052A scalar reference prototype now correctly allows a hash or
a5222a85
GS
1053array element in that slot.
1054
1055=head2 Pseudo-hashes work better
1056
1057Dereferencing some types of reference values in a pseudo-hash,
c47ff5f1 1058such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
a5222a85
GS
1059been corrected.
1060
1061When applied to a pseudo-hash element, exists() now reports whether
1062the specified value exists, not merely if the key is valid.
1063
01020589
GS
1064delete() now works on pseudo-hashes. When given a pseudo-hash element
1065or slice it deletes the values corresponding to the keys (but not the keys
1066themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1067
479ba383
GS
1068Pseudo-hash slices with constant keys are now optimized to array lookups
1069at compile-time.
1070
1071The C<fields> pragma now provides ways to create pseudo-hashes, via
1072fields::new() and fields::phash(). See L<fields>.
1073
a5222a85
GS
1074=head2 C<goto &sub> and AUTOLOAD
1075
08cd8952 1076The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
1077to be autoloaded.
1078
1079=head2 C<-bareword> allowed under C<use integer>
1080
1081The autoquoting of barewords preceded by C<-> did not work
1082in prior versions when the C<integer> pragma was enabled.
1083This has been fixed.
1084
1085=head2 Boolean assignment operators are legal lvalues
1086
1087Constructs such as C<($a ||= 2) += 1> are now allowed.
1088
1089=head2 C<sort $coderef @foo> allowed
1090
1091sort() did not accept a subroutine reference as the comparison
08cd8952 1092function in earlier versions. This is now permitted.
a5222a85
GS
1093
1094=head2 Failures in DESTROY()
1095
1096When code in a destructor threw an exception, it went unnoticed
1097in earlier versions of Perl, unless someone happened to be
1098looking in $@ just after the point the destructor happened to
1099run. Such failures are now visible as warnings when warnings are
1100enabled.
1101
1102=head2 Locale bugs fixed
54195c32 1103
437784d6 1104printf() and sprintf() previously reset the numeric locale
67d3893f
JH
1105back to the default "C" locale. This has been fixed.
1106
1107Numbers formatted according to the local numeric locale
1108(such as using a decimal comma instead of a decimal dot) caused
1109"isn't numeric" warnings, even while the operations accessing
642f9deb
GS
1110those numbers produced correct results. These warnings have been
1111discontinued.
54195c32 1112
a5222a85
GS
1113=head2 Memory leaks
1114
1115The C<eval 'return sub {...}'> construct could sometimes leak
1116memory. This has been fixed.
1117
1118Operations that aren't filehandle constructors used to leak memory
1119when used on invalid filehandles. This has been fixed.
1120
1121Constructs that modified C<@_> could fail to deallocate values
1122in C<@_> and thus leak memory. This has been corrected.
1123
1124=head2 Spurious subroutine stubs after failed subroutine calls
1125
1126Perl could sometimes create empty subroutine stubs when a
1127subroutine was not found in the package. Such cases stopped
1128later method lookups from progressing into base packages.
1129This has been corrected.
1130
a5222a85
GS
1131=head2 Taint failures under C<-U>
1132
1133When running in unsafe mode, taint violations could sometimes
1134cause silent failures. This has been fixed.
1135
1136=head2 END blocks and the C<-c> switch
1137
1138Prior versions used to run BEGIN B<and> END blocks when Perl was
1139run in compile-only mode. Since this is typically not the expected
08cd8952 1140behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
1141is used.
1142
7d30b5c4 1143See L<CHECK blocks> for how to run things when the compile phase ends.
a5222a85
GS
1144
1145=head2 Potential to leak DATA filehandles
1146
1147Using the C<__DATA__> token creates an implicit filehandle to
1148the file that contains the token. It is the program's
1149responsibility to close it when it is done reading from it.
1150
1151This caveat is now better explained in the documentation.
1152See L<perldata>.
1153
1154=head2 Diagnostics follow STDERR
1155
1156Diagnostic output now goes to whichever file the C<STDERR> handle
1157is pointing at, instead of always going to the underlying C runtime
1158library's C<stderr>.
1159
1160=head2 Other fixes for better diagnostics
1161
437784d6 1162Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
1163during the global destruction phase.
1164
1165Diagnostics emitted from code running in threads other than the main
1166thread are now accompanied by the thread ID.
1167
1168Embedded null characters in diagnostics now actually show up. They
1169used to truncate the message in prior versions.
1170
1171$foo::a and $foo::b are now exempt from "possible typo" warnings only
642f9deb 1172if sort() is encountered in package C<foo>.
a5222a85 1173
501fbaef 1174Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
1175constructs now generate a warning, since they may take on new
1176semantics in later versions of Perl.
1177
a398b1cd
GS
1178Many diagnostics now report the internal operation in which the warning
1179was provoked, like so:
1180
1181 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1182 Use of uninitialized value in print at (eval 1) line 1.
1183
1184Diagnostics that occur within eval may also report the file and line
1185number where the eval is located, in addition to the eval sequence
1186number and the line number within the evaluated text itself. For
1187example:
1188
1189 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1190
a5222a85
GS
1191=head1 Performance enhancements
1192
1193=head2 Simple sort() using { $a <=> $b } and the like are optimized
1194
08cd8952 1195Many common sort() operations using a simple inlined block are now
a5222a85
GS
1196optimized for faster performance.
1197
1198=head2 Optimized assignments to lexical variables
1199
1200Certain operations in the RHS of assignment statements have been
1201optimized to directly set the lexical variable on the LHS,
1202eliminating redundant copying overheads.
1203
a5222a85
GS
1204=head2 Faster subroutine calls
1205
1206Minor changes in how subroutine calls are handled internally
1207provide marginal improvements in performance.
1208
1209=head1 Platform specific changes
1210
063663a9 1211=head2 Supported platforms
ba8251e8 1212
5fdc711f
GS
1213=over 4
1214
1215=item *
1216
6c67e1bb
TC
1217VM/ESA is now supported.
1218
5fdc711f
GS
1219=item *
1220
ee3907e2
JH
1221Siemens BS2000 is now supported under the POSIX Shell.
1222
1223=item *
1224
2bb14304
JH
1225The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1226extension.
6c67e1bb 1227
5fdc711f
GS
1228=item *
1229
ee3907e2 1230GNU/Hurd is now supported.
6c67e1bb 1231
00ad96e1
JH
1232=item *
1233
063663a9 1234Rhapsody/Darwin is now supported.
00ad96e1 1235
27806c82
JH
1236=item *
1237
1238EPOC is is now supported (on Psion 5).
1239
5fdc711f
GS
1240=back
1241
a5222a85
GS
1242=head2 DOS
1243
d524f05e
LM
1244=over 4
1245
1246=item *
1247
1248Perl now works with djgpp 2.02 (and 2.03 alpha).
1249
1250=item *
1251
1252Environment variable names are not converted to uppercase any more.
1253
1254=item *
1255
642f9deb 1256Incorrect exit codes from backticks have been fixed.
d524f05e
LM
1257
1258=item *
1259
642f9deb 1260This port continues to use its own builtin globbing (not File::Glob).
d524f05e
LM
1261
1262=back
a5222a85 1263
c6018dae 1264=head2 OS390 (OpenEdition MVS)
063663a9
GS
1265
1266Support for this EBCDIC platform has not been renewed in this release.
1267There are difficulties in reconciling Perl's standardization on UTF-8
1268as its internal representation for characters with the EBCDIC character
1269set, because the two are incompatible.
1270
1271It is unclear whether future versions will renew support for this
1272platform, but the possibility exists.
1273
a5222a85
GS
1274=head2 VMS
1275
c93fa817 1276Numerous revisions and extensions to configuration, build, testing, and
642f9deb 1277installation process to accomodate core changes and VMS-specific options.
c93fa817
GS
1278
1279Expand %ENV-handling code to allow runtime mapping to logical names,
642f9deb 1280CLI symbols, and CRTL environ array.
c93fa817 1281
642f9deb
GS
1282Extension of subprocess invocation code to accept filespecs as command
1283"verbs".
c93fa817
GS
1284
1285Add to Perl command line processing the ability to use default file types and
642f9deb 1286to recognize Unix-style C<2E<gt>&1>.
c93fa817 1287
642f9deb 1288Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
c93fa817 1289
642f9deb 1290Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
c93fa817
GS
1291
1292Barewords at start of Unix-syntax paths may be treated as text rather than
642f9deb 1293only as logical names.
c93fa817 1294
642f9deb 1295Optional secure translation of several logical names used internally by Perl.
c93fa817 1296
642f9deb 1297Miscellaneous bugfixing and porting of new core code to VMS.
c93fa817
GS
1298
1299Thanks are gladly extended to the many people who have contributed VMS
1300patches, testing, and ideas.
a5222a85
GS
1301
1302=head2 Win32
1303
642f9deb
GS
1304Perl can now emulate fork() internally, using multiple interpreters running
1305in different concurrent threads. This support must be enabled at build
1306time. See L<perlfork> for detailed information.
a5222a85 1307
642f9deb
GS
1308When given a pathname that consists only of a drivename, such as C<A:>,
1309opendir() and stat() now use the current working directory for the drive
1310rather than the drive root.
a5222a85 1311
642f9deb
GS
1312The builtin XSUB functions in the Win32:: namespace are documented. See
1313L<Win32>.
a5222a85
GS
1314
1315$^X now contains the full path name of the running executable.
1316
1317A Win32::GetLongPathName() function is provided to complement
1318Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1319
1320POSIX::uname() is supported.
1321
1322system(1,...) now returns true process IDs rather than process
1323handles. kill() accepts any real process id, rather than strictly
1324return values from system(1,...).
1325
42b8b86c
GS
1326For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1327test whether a process exists.
1328
a5222a85
GS
1329The C<Shell> module is supported.
1330
642f9deb 1331Better support for building Perl under command.com in Windows 95
883d36a6
GS
1332has been added.
1333
c39cd008
GS
1334Scripts are read in binary mode by default to allow ByteLoader (and
1335the filter mechanism in general) to work properly. For compatibility,
53129d29
GS
1336the DATA filehandle will be set to text mode if a carriage return is
1337detected at the end of the line containing the __END__ or __DATA__
1338token; if not, the DATA filehandle will be left open in binary mode.
1339Earlier versions always opened the DATA filehandle in text mode.
c39cd008 1340
3a4b19e4 1341The glob() operator is implemented via the C<File::Glob> extension,
8004f2ac 1342which supports glob syntax of the C shell. This increases the flexibility
16070b82
GS
1343of the glob() operator, but there may be compatibility issues for
1344programs that relied on the older globbing syntax. If you want to
642f9deb
GS
1345preserve compatibility with the older syntax, you might want to run
1346perl with C<-MFile::DosGlob>. For details and compatibility information,
1347see L<File::Glob>.
16070b82 1348
6c67e1bb
TC
1349=head1 New tests
1350
1351=over 4
1352
09bef843
SB
1353=item lib/attrs
1354
1355Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1356
2675e62c
GS
1357=item lib/env
1358
1359Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1360
1361=item lib/env-array
1362
1363Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1364
09bef843 1365=item lib/io_const
6c67e1bb
TC
1366
1367IO constants (SEEK_*, _IO*).
14218588 1368
09bef843 1369=item lib/io_dir
6c67e1bb
TC
1370
1371Directory-related IO methods (new, read, close, rewind, tied delete).
1372
09bef843 1373=item lib/io_multihomed
6c67e1bb
TC
1374
1375INET sockets with multi-homed hosts.
1376
09bef843 1377=item lib/io_poll
6c67e1bb
TC
1378
1379IO poll().
1380
09bef843 1381=item lib/io_unix
6c67e1bb
TC
1382
1383UNIX sockets.
1384
09bef843
SB
1385=item op/attrs
1386
1387Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1388
6c67e1bb
TC
1389=item op/filetest
1390
1391File test operators.
1392
1393=item op/lex_assign
1394
5fdc711f 1395Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb 1396
afebc493
GS
1397=item op/exists_sub
1398
1399Verify C<exists &sub> operations.
1400
6c67e1bb 1401=back
e02fdbd2 1402
ba8251e8
GS
1403=head1 Modules and Pragmata
1404
3e8c4fa0
JH
1405=head2 Modules
1406
b7d8191e
JH
1407=over 4
1408
09bef843
SB
1409=item attributes
1410
1411While used internally by Perl as a pragma, this module also
1412provides a way to fetch subroutine and variable attributes.
1413See L<attributes>.
1414
a5222a85
GS
1415=item B
1416
642f9deb
GS
1417 WARNING: The Compiler suite remains highly experimental. The
1418 generated code may not be correct, even it manages to execute
1419 without errors.
501fbaef 1420
c6018dae
GS
1421The Perl Compiler suite has been extensively reworked for this
1422release. More of the standard Perl testsuite passes when run
1423under the Compiler, but there is still a significant way to
1424go to achieve production quality compiled executables.
a5222a85 1425
f29c64d6
GS
1426=item ByteLoader
1427
a5222a85 1428The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1429Perl bytecode. See L<ByteLoader>.
1430
a5222a85
GS
1431=item constant
1432
83763826
GS
1433References can now be used.
1434
1435The new version also allows a leading underscore in constant names, but
1436disallows a double leading underscore (as in "__LINE__"). Some other names
1437are disallowed or warned against, including BEGIN, END, etc. Some names
1438which were forced into main:: used to fail silently in some cases; now they're
1439fatal (outside of main::) and an optional warning (inside of main::).
1440The ability to detect whether a constant had been set with a given name has
1441been added.
1442
1443See L<constant>.
a5222a85
GS
1444
1445=item charnames
1446
21bad921 1447This pragma implements the C<\N> string escape. See L<charnames>.
a5222a85
GS
1448
1449=item Data::Dumper
1450
1451A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1452too deeply into deep data structures. See L<Data::Dumper>.
a5222a85 1453
0f1923bd
GS
1454The XSUB implementation of Dump() is now automatically called if the
1455C<Useqq> setting is not in use.
1456
a5222a85
GS
1457Dumping C<qr//> objects works correctly.
1458
1459=item DB
1460
1461C<DB> is an experimental module that exposes a clean abstraction
1462to Perl's debugging API.
1463
1464=item DB_File
1465
0536e0eb
GS
1466DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1467See C<ext/DB_File/Changes>.
a5222a85 1468
f29c64d6
GS
1469=item Devel::DProf
1470
9e107c59
GS
1471Devel::DProf, a Perl source code profiler has been added. See
1472L<Devel::DProf> and L<dprofpp>.
f29c64d6 1473
b7d8191e
JH
1474=item Dumpvalue
1475
437784d6 1476The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1477
1478=item Benchmark
1479
54e82ce5
GS
1480Overall, Benchmark results exhibit lower average error and better timing
1481accuracy.
1482
868cb350 1483You can now run tests for I<n> seconds instead of guessing the right
642f9deb 1484number of tests to run: e.g., timethese(-5, ...) will run each
14218588 1485code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1486means "for at least 3 CPU seconds". The output format has also
14218588 1487changed. For example:
155776c0 1488
54e82ce5 1489 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1490
1491will now output something like this:
1492
54e82ce5
GS
1493 Benchmark: running a, b, each for at least 5 CPU seconds...
1494 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1495 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1496
1497New features: "each for at least N CPU seconds...", "wallclock secs",
1498and the "@ operations/CPU second (n=operations)".
b7d8191e 1499
54e82ce5
GS
1500timethese() now returns a reference to a hash of Benchmark objects containing
1501the test results, keyed on the names of the tests.
1502
1503timethis() now returns the iterations field in the Benchmark result object
1504instead of 0.
1505
1506timethese(), timethis(), and the new cmpthese() (see below) can also take
1507a format specifier of 'none' to suppress output.
1508
1509A new function countit() is just like timeit() except that it takes a
1510TIME instead of a COUNT.
1511
1512A new function cmpthese() prints a chart comparing the results of each test
1513returned from a timethese() call. For each possible pair of tests, the
1514percentage speed difference (iters/sec or seconds/iter) is shown.
1515
1516For other details, see L<Benchmark>.
a5222a85 1517
f505c983
GS
1518=item Devel::Peek
1519
1520The Devel::Peek module provides access to the internal representation
14218588 1521of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1522
44dcb63b
GS
1523=item English
1524
1525$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1526(a numeric value).
1527
2675e62c
GS
1528=item Env
1529
1530Env now supports accessing environment variables like PATH as array
1531variables.
1532
b7d8191e
JH
1533=item Fcntl
1534
1535More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
55f6b6ec
JH
1536large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1537automatically added to sysopen() flags if large file support has been
1538configured, as is the default), Free/Net/OpenBSD locking behaviour
1539flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1540mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1541constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1542C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1543are available via the C<:mode> tag.
b7d8191e 1544
a5222a85
GS
1545=item File::Compare
1546
1547A compare_text() function has been added, which allows custom
1548comparison functions. See L<File::Compare>.
1549
1550=item File::Find
1551
1552File::Find now works correctly when the wanted() function is either
1553autoloaded or is a symbolic reference.
1554
08cd8952 1555A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1556when pruning top-level directories has been fixed.
1557
81793b90
GS
1558File::Find now also supports several other options to control its
1559behavior. It can follow symbolic links if the C<follow> option is
1560specified. Enabling the C<no_chdir> option will make File::Find skip
1561changing the current directory when walking directories. The C<untaint>
1562flag can be useful when running with taint checks enabled.
1563
1564See L<File::Find>.
1565
becf2bd3
GS
1566=item File::Glob
1567
52bb0670
GS
1568This extension implements BSD-style file globbing. By default,
1569it will also be used for the internal implementation of the glob()
1570operator. See L<File::Glob>.
becf2bd3 1571
f505c983
GS
1572=item File::Spec
1573
1574New methods have been added to the File::Spec module: devnull() returns
19799a22 1575the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1576the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1577to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1578rel2abs(). For compatibility with operating systems that specify volume
1579names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1580have been added.
1581
1582=item File::Spec::Functions
1583
1584The new File::Spec::Functions modules provides a function interface
14218588 1585to the File::Spec module. Allows shorthand
f505c983 1586
14218588 1587 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1588
1589instead of
1590
14218588 1591 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1592
a5222a85
GS
1593=item Getopt::Long
1594
c6edd1b7
GS
1595Getopt::Long licensing has changed to allow the Perl Artistic License
1596as well as the GPL. It used to be GPL only, which got in the way of
1597non-GPL applications that wanted to use Getopt::Long.
1598
1599Getopt::Long encourages the use of Pod::Usage to produce help
1600messages. For example:
1601
1602 use Getopt::Long;
1603 use Pod::Usage;
1604 my $man = 0;
1605 my $help = 0;
1606 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1607 pod2usage(1) if $help;
1608 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1609
1610 __END__
1611
1612 =head1 NAME
1613
1614 sample - Using GetOpt::Long and Pod::Usage
1615
1616 =head1 SYNOPSIS
1617
1618 sample [options] [file ...]
1619
1620 Options:
1621 -help brief help message
1622 -man full documentation
1623
1624 =head1 OPTIONS
1625
1626 =over 8
1627
1628 =item B<-help>
1629
1630 Print a brief help message and exits.
1631
1632 =item B<-man>
1633
1634 Prints the manual page and exits.
1635
1636 =back
1637
1638 =head1 DESCRIPTION
1639
1640 B<This program> will read the given input file(s) and do someting
1641 useful with the contents thereof.
1642
1643 =cut
1644
1645See L<Pod::Usage> for details.
1646
c47ff5f1 1647A bug that prevented the non-option call-back <> from being
c6edd1b7
GS
1648specified as the first argument has been fixed.
1649
c47ff5f1
GS
1650To specify the characters < and > as option starters, use ><. Note,
1651however, that changing option starters is strongly deprecated.
a5222a85
GS
1652
1653=item IO
1654
1655write() and syswrite() will now accept a single-argument
1656form of the call, for consistency with Perl's syswrite().
1657
1658You can now create a TCP-based IO::Socket::INET without forcing
1659a connect attempt. This allows you to configure its options
1660(like making it non-blocking) and then call connect() manually.
1661
1662A bug that prevented the IO::Socket::protocol() accessor
1663from ever returning the correct value has been corrected.
1664
36f31b50
GS
1665IO::Socket::connect now uses non-blocking IO instead of alarm()
1666to do connect timeouts.
1667
1668IO::Socket::accept now uses select() instead of alarm() for doing
1669timeouts.
1670
1671IO::Socket::INET->new now sets $! correctly on failure. $@ is
1672still set for backwards compatability.
1673
a5222a85
GS
1674=item JPL
1675
1676Java Perl Lingo is now distributed with Perl. See jpl/README
1677for more information.
1678
883d36a6
GS
1679=item lib
1680
1681C<use lib> now weeds out any trailing duplicate entries.
1682C<no lib> removes all named entries.
1683
e16b8f49
WM
1684=item Math::BigInt
1685
c47ff5f1 1686The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
e16b8f49
WM
1687and C<~> are now supported on bigints.
1688
b7d8191e 1689=item Math::Complex
7711098a 1690
14218588 1691The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1692act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e 1693
16357284
JH
1694The class method C<display_format> and the corresponding object method
1695C<display_format>, in addition to accepting just one argument, now can
1696also accept a parameter hash. Recognized keys of a parameter hash are
1697C<"style">, which corresponds to the old one parameter case, and two
1698new parameters: C<"format">, which is a printf()-style format string
1699(defaults usually to C<"%.15g">, you can revert to the default by
1700setting the format string to C<undef>) used for both parts of a
1701complex number, and C<"polar_pretty_print"> (defaults to true),
1702which controls whether an attempt is made to try to recognize small
1703multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1704polar complex number.
1705
1706The potentially disruptive change is that in list context both methods
1707now I<return the parameter hash>, instead of only the value of the
1708C<"style"> parameter.
1709
b7d8191e
JH
1710=item Math::Trig
1711
14218588
GS
1712A little bit of radial trigonometry (cylindrical and spherical),
1713radial coordinate conversions, and the great circle distance were added.
b7d8191e 1714
1761cee5 1715=item Pod::Parser, Pod::InputObjects
d4629d6a 1716
1761cee5
JH
1717Pod::Parser is a base class for parsing and selecting sections of
1718pod documentation from an input stream. This module takes care of
1719identifying pod paragraphs and commands in the input and hands off the
1720parsed paragraphs and commands to user-defined methods which are free
1721to interpret or translate them as they see fit.
d4629d6a
GS
1722
1723Pod::InputObjects defines some input objects needed by Pod::Parser, and
1724for advanced users of Pod::Parser that need more about a command besides
1761cee5 1725its name and text.
d4629d6a 1726
21bad921 1727As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
d4629d6a
GS
1728"base parser code" recommended for use by all pod2xxx translators.
1729Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1761cee5
JH
1730to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1731underway. For any questions or comments about pod parsing and translating
1732issues and utilities, please use the pod-people@perl.org mailing list.
d4629d6a 1733
1761cee5 1734For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
d4629d6a 1735
1761cee5 1736=item Pod::Checker, podchecker
d4629d6a 1737
1761cee5
JH
1738This utility checks pod files for correct syntax, according to
1739L<perlpod>. Obvious errors are flagged as such, while warnings are
1740printed for mistakes that can be handled gracefully. The checklist is
1741not complete yet. See L<Pod::Checker>.
d4629d6a 1742
1761cee5 1743=item Pod::ParseUtils, Pod::Find
d4629d6a 1744
1761cee5
JH
1745These modules provide a set of gizmos that are useful mainly for pod
1746translators. L<Pod::Find|Pod::Find> traverses directory structures and
1747returns found pod files, along with their canonical names (like
1748C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1749B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
c47ff5f1 1750(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
642f9deb 1751(for caching information about pod files, e.g., link nodes).
d4629d6a 1752
1761cee5 1753=item Pod::Select, podselect
d4629d6a 1754
1761cee5
JH
1755Pod::Select is a subclass of Pod::Parser which provides a function
1756named "podselect()" to filter out user-specified sections of raw pod
1757documentation from an input stream. podselect is a script that provides
1758access to Pod::Select from other scripts to be used as a filter.
1759See L<Pod::Select>.
d4629d6a 1760
1761cee5 1761=item Pod::Usage, pod2usage
d4629d6a 1762
1761cee5
JH
1763Pod::Usage provides the function "pod2usage()" to print usage messages for
1764a Perl script based on its embedded pod documentation. The pod2usage()
1765function is generally useful to all script authors since it lets them
1766write and maintain a single source (the pods) for documentation, thus
1767removing the need to create and maintain redundant usage message text
1768consisting of information already in the pods.
d4629d6a 1769
1761cee5
JH
1770There is also a pod2usage script which can be used from other kinds of
1771scripts to print usage messages from pods (even for non-Perl scripts
1772with pods embedded in comments).
a5222a85 1773
1761cee5 1774For details and examples, please see L<Pod::Usage>.
a5222a85
GS
1775
1776=item Pod::Text and Pod::Man
1777
e3e5e1ea
GS
1778Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1779still available for backwards compatibility, the module now has a new
1780preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1781module is easily subclassed for tweaks to the output, and two such
1782subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1783using termcap information, and Pod::Text::Color for markup with ANSI color
1784sequences) are now standard.
1785
1786pod2man has been turned into a module, Pod::Man, which also uses
1787Pod::Parser. In the process, several outstanding bugs related to quotes
1788in section headers, quoting of code escapes, and nested lists have been
1789fixed. pod2man is now a wrapper script around this module.
a5222a85 1790
f4b9d880
RA
1791=item SDBM_File
1792
1793An EXISTS method has been added to this module (and sdbm_exists() has
1794been added to the underlying sdbm library), so one can now call exists
14218588 1795on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1796runtime error.
1797
a5222a85
GS
1798A bug that may have caused data loss when more than one disk block
1799happens to be read from the database in a single FETCH() has been
1800fixed.
1801
8ce86de8
GS
1802=item Sys::Syslog
1803
1804Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1805no longer requires syslog.ph to exist.
1806
f91101c9
GS
1807=item Sys::Hostname
1808
1809Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1810uname() if they exist.
1811
e3e5e1ea
GS
1812=item Term::ANSIColor
1813
1814Term::ANSIColor is a very simple module to provide easy and readable
1815access to the ANSI color and highlighting escape sequences, supported by
1816most ANSI terminal emulators. It is now included standard.
1817
06ef4121
PC
1818=item Time::Local
1819
1820The timelocal() and timegm() functions used to silently return bogus
437784d6 1821results when the date fell outside the machine's integer range. They
a5222a85 1822now consistently croak() if the date falls in an unsupported range.
06ef4121 1823
8fe0a5c4
JD
1824=item Win32
1825
1826The error return value in list context has been changed for all functions
14218588
GS
1827that return a list of values. Previously these functions returned a list
1828with a single element C<undef> if an error occurred. Now these functions
1829return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1830functions:
1831
14218588
GS
1832 Win32::FsType
1833 Win32::GetOSVersion
8fe0a5c4
JD
1834
1835The remaining functions are unchanged and continue to return C<undef> on
1836error even in list context.
1837
1838The Win32::SetLastError(ERROR) function has been added as a complement
1839to the Win32::GetLastError() function.
1840
1841The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1842pathname for FILENAME in scalar context. In list context it returns
1843a two-element list containing the fully qualified directory name and
501fbaef 1844the filename. See L<Win32>.
8fe0a5c4 1845
9fe6733a
PM
1846=item DBM Filters
1847
1848A new feature called "DBM Filters" has been added to all the
14218588
GS
1849DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1850DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1851
1852 filter_store_key
1853 filter_store_value
1854 filter_fetch_key
1855 filter_fetch_value
1856
14218588 1857These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1858written to the database or just after they are read from the database.
1859See L<perldbmfilter> for further information.
1860
b7d8191e 1861=back
3e8c4fa0
JH
1862
1863=head2 Pragmata
1864
437784d6 1865C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1866backward-compatibility. It's been replaced by the C<sub : attributes>
1867syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1868
4438c4b7 1869Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1870See L<perllexwarn>.
6c67e1bb 1871
67d3893f
JH
1872C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1873...). Currently only one subpragma implemented, "use filetest
1874'access';", that uses access(2) or equivalent to check permissions
1875instead of using stat(2) as usual. This matters in filesystems
1876where there are ACLs (access control lists): the stat(2) might lie,
1877but access(2) knows better.
6c67e1bb 1878
ba8251e8
GS
1879=head1 Utility Changes
1880
a5222a85
GS
1881=head2 perlcc
1882
1883C<perlcc> now supports the C and Bytecode backends. By default,
1884it generates output from the simple C backend rather than the
1885optimized C backend.
1886
1887Support for non-Unix platforms has been improved.
1888
055fd3a9
GS
1889=head2 perldoc
1890
1891C<perldoc> has been reworked to avoid possible security holes.
1892It will not by default let itself be run as the superuser, but you
1893may still use the B<-U> switch to try to make it drop privileges
1894first.
1895
1896=head2 The Perl Debugger
1897
1898Many bug fixes and enhancements were added to F<perl5db.pl>, the
1899Perl debugger. The help documentation was rearranged. New commands
1900include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1901actions, C<man I<docpage>> to run your doc viewer on some perl
1902docset, and support for quoted options. The help information was
1903rearranged, and should be viewable once again if you're using B<less>
1904as your pager. A serious security hole was plugged--you should
1905immediately remove all older versions of the Perl debugger as
1906installed in previous releases, all the way back to perl3, from
1907your system to avoid being bitten by this.
1908
ba8251e8
GS
1909=head1 Documentation Changes
1910
5fdc711f
GS
1911=over 4
1912
954c1994
GS
1913=item perlapi.pod
1914
1915The official list of public Perl API functions.
1916
883d36a6
GS
1917=item perlcompile.pod
1918
1919An introduction to using the Perl Compiler suite.
1920
055fd3a9
GS
1921=item perldebug.pod
1922
1923All material unrelated to running the Perl debugger, plus all
1924low-level guts-like details that risked crushing the casual user
1925of the debugger, have been relocated from the old manpage to the
1926next entry below.
1927
1928=item perldebguts.pod
1929
1930This new manpage contains excessively low-level material not related
1931to the Perl debugger, but slightly related to debugging Perl itself.
1932It also contains some arcane internal details of how the debugging
1933process works that may only be of interest to developers of Perl
1934debuggers.
1935
c7c04614
GS
1936=item perlfilter.pod
1937
1938An introduction to writing Perl source filters.
1939
883d36a6
GS
1940=item perlhack.pod
1941
1942Some guidelines for hacking the Perl source code.
1943
954c1994
GS
1944=item perlintern.pod
1945
1946A list of internal functions in the Perl source code.
1947(List is currently empty.)
1948
5fdc711f 1949=item perlopentut.pod
f8284313 1950
5fdc711f
GS
1951A tutorial on using open() effectively.
1952
1953=item perlreftut.pod
1954
1955A tutorial that introduces the essentials of references.
1956
694468e3
GS
1957=item perlboot.pod
1958
1959A tutorial for beginners on object-oriented Perl.
1960
14218588
GS
1961=item perltootc.pod
1962
1963A tutorial on managing class data for object modules.
1964
393fec97
GS
1965=item perlunicode.pod
1966
1967An introduction to Unicode support features in Perl.
1968
5fdc711f 1969=back
e02fdbd2 1970
73b437c8 1971=head1 New or Changed Diagnostics
ba8251e8 1972
a99ba403
GS
1973=over 4
1974
56e90b21
GS
1975=item "%s" variable %s masks earlier declaration in same %s
1976
ddda08b7 1977(W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
56e90b21
GS
1978effectively eliminating all access to the previous instance. This is almost
1979always a typographical error. Note that the earlier variable will still exist
1980until the end of the scope or until all closure referents to it are
1981destroyed.
1982
33633739
GS
1983=item "my sub" not yet implemented
1984
1985(F) Lexically scoped subroutines are not yet implemented. Don't try that
1986yet.
1987
1988=item "our" variable %s redeclared
1989
ddda08b7 1990(W misc) You seem to have already declared the same global once before in the
33633739
GS
1991current lexical scope.
1992
a99ba403
GS
1993=item '!' allowed only after types %s
1994
1995(F) The '!' is allowed in pack() and unpack() only after certain types.
1996See L<perlfunc/pack>.
1997
1998=item / cannot take a count
1999
2000(F) You had an unpack template indicating a counted-length string,
2001but you have also specified an explicit size for the string.
2002See L<perlfunc/pack>.
2003
2004=item / must be followed by a, A or Z
2005
2006(F) You had an unpack template indicating a counted-length string,
2007which must be followed by one of the letters a, A or Z
2008to indicate what sort of string is to be unpacked.
2009See L<perlfunc/pack>.
2010
2011=item / must be followed by a*, A* or Z*
2012
437784d6 2013(F) You had a pack template indicating a counted-length string,
a99ba403
GS
2014Currently the only things that can have their length counted are a*, A* or Z*.
2015See L<perlfunc/pack>.
2016
2017=item / must follow a numeric type
2018
2019(F) You had an unpack template that contained a '#',
2020but this did not follow some numeric unpack specification.
2021See L<perlfunc/pack>.
2022
a99ba403
GS
2023=item /%s/: Unrecognized escape \\%c passed through
2024
ddda08b7 2025(W regexp) You used a backslash-character combination which is not recognized
a99ba403 2026by Perl. This combination appears in an interpolated variable or a
1028017a
JH
2027C<'>-delimited regular expression. The character was understood literally.
2028
2029=item /%s/: Unrecognized escape \\%c in character class passed through
2030
ddda08b7 2031(W regexp) You used a backslash-character combination which is not recognized
1028017a 2032by Perl inside character classes. The character was understood literally.
a99ba403
GS
2033
2034=item /%s/ should probably be written as "%s"
2035
ddda08b7 2036(W syntax) You have used a pattern where Perl expected to find a string,
437784d6 2037as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
2038or false result of matching the pattern against $_ as the string,
2039which is probably not what you had in mind.
2040
2041=item %s() called too early to check prototype
2042
ddda08b7 2043(W prototype) You've called a function that has a prototype before the parser saw a
a99ba403
GS
2044definition or declaration for it, and Perl could not check that the call
2045conforms to the prototype. You need to either add an early prototype
2046declaration for the subroutine in question, or move the subroutine
2047definition ahead of the call to get proper prototype checking. Alternatively,
2048if you are certain that you're calling the function correctly, you may put
2049an ampersand before the name to avoid the warning. See L<perlsub>.
2050
56e90b21
GS
2051=item %s argument is not a HASH or ARRAY element
2052
2053(F) The argument to exists() must be a hash or array element, such as:
2054
2055 $foo{$bar}
2056 $ref->[12]->["susie"]
2057
2058=item %s argument is not a HASH or ARRAY element or slice
2059
2060(F) The argument to delete() must be either a hash or array element, such as:
2061
2062 $foo{$bar}
2063 $ref->[12]->["susie"]
2064
2065or a hash or array slice, such as:
2066
2067 @foo[$bar, $baz, $xyzzy]
2068 @{$ref->[12]}{"susie", "queue"}
2069
afebc493
GS
2070=item %s argument is not a subroutine name
2071
2072(F) The argument to exists() for C<exists &sub> must be a subroutine
2073name, and not a subroutine call. C<exists &sub()> will generate this error.
2074
09bef843
SB
2075=item %s package attribute may clash with future reserved word: %s
2076
ddda08b7 2077(W reserved) A lowercase attribute name was used that had a package-specific handler.
09bef843
SB
2078That name might have a meaning to Perl itself some day, even though it
2079doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2080See L<attributes>.
2081
cc507455 2082=item (in cleanup) %s
6b121555 2083
ddda08b7 2084(W misc) This prefix usually indicates that a DESTROY() method raised
a99ba403
GS
2085the indicated exception. Since destructors are usually called by
2086the system at arbitrary points during execution, and often a vast
2087number of times, the warning is issued only once for any number
2088of failures that would otherwise result in the same message being
2089repeated.
2090
2091Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2092could also result in this warning. See L<perlcall/G_KEEPERR>.
2093
2094=item <> should be quotes
2095
c47ff5f1 2096(F) You wrote C<< require <file> >> when you should have written
a99ba403
GS
2097C<require 'file'>.
2098
2099=item Attempt to join self
2100
2101(F) You tried to join a thread from within itself, which is an
2102impossible task. You may be joining the wrong thread, or you may
2103need to move the join() to some other thread.
2104
2105=item Bad evalled substitution pattern
2106
2107(F) You've used the /e switch to evaluate the replacement for a
2108substitution, but perl found a syntax error in the code to evaluate,
2109most likely an unexpected right brace '}'.
2110
2111=item Bad realloc() ignored
2112
2113(S) An internal routine called realloc() on something that had never been
2114malloc()ed in the first place. Mandatory, but can be disabled by
2115setting environment variable C<PERL_BADFREE> to 1.
2116
34d09196
GS
2117=item Bareword found in conditional
2118
ddda08b7 2119(W bareword) The compiler found a bareword where it expected a conditional,
34d09196
GS
2120which often indicates that an || or && was parsed as part of the
2121last argument of the previous construct, for example:
2122
2123 open FOO || die;
2124
2125It may also indicate a misspelled constant that has been interpreted
2126as a bareword:
2127
2128 use constant TYPO => 1;
2129 if (TYOP) { print "foo" }
2130
2131The C<strict> pragma is useful in avoiding such errors.
2132
a99ba403
GS
2133=item Binary number > 0b11111111111111111111111111111111 non-portable
2134
ddda08b7 2135(W portable) The binary number you specified is larger than 2**32-1
a99ba403
GS
2136(4294967295) and therefore non-portable between systems. See
2137L<perlport> for more on portability concerns.
2138
2139=item Bit vector size > 32 non-portable
2140
ddda08b7 2141(W portable) Using bit vector sizes larger than 32 is non-portable.
a99ba403
GS
2142
2143=item Buffer overflow in prime_env_iter: %s
2144
ddda08b7 2145(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
a99ba403
GS
2146%ENV, it encountered a logical name or symbol definition which was too long,
2147so it was truncated to the string shown.
2148
2149=item Can't check filesystem of script "%s"
2150
2151(P) For some reason you can't check the filesystem of the script for nosuid.
2152
56e90b21
GS
2153=item Can't declare class for non-scalar %s in "%s"
2154
2155(S) Currently, only scalar variables can declared with a specific class
2156qualifier in a "my" or "our" declaration. The semantics may be extended
2157for other types of variables in future.
2158
2159=item Can't declare %s in "%s"
2160
2161(F) Only scalar, array, and hash variables may be declared as "my" or
2162"our" variables. They must have ordinary identifiers as names.
2163
0b5b802d
GS
2164=item Can't ignore signal CHLD, forcing to default
2165
ddda08b7 2166(W signal) Perl has detected that it is being run with the SIGCHLD signal
0b5b802d
GS
2167(sometimes known as SIGCLD) disabled. Since disabling this signal
2168will interfere with proper determination of exit status of child
2169processes, Perl has reset the signal to its default value.
2170This situation typically indicates that the parent program under
642f9deb 2171which Perl may be running (e.g., cron) is being very careless.
0b5b802d 2172
a99ba403
GS
2173=item Can't modify non-lvalue subroutine call
2174
437784d6
GS
2175(F) Subroutines meant to be used in lvalue context should be declared as
2176such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
2177
2178=item Can't read CRTL environ
2179
2180(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2181from the CRTL's internal environment array and discovered the array was
2182missing. You need to figure out where your CRTL misplaced its environ
2183or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2184
2185=item Can't remove %s: %s, skipping file
2186
2187(S) You requested an inplace edit without creating a backup file. Perl
2188was unable to remove the original file to replace it with the modified
2189file. The file was left unmodified.
2190
2191=item Can't return %s from lvalue subroutine
2192
2193(F) Perl detected an attempt to return illegal lvalues (such
2194as temporary or readonly values) from a subroutine used as an lvalue.
2195This is not allowed.
2196
2197=item Can't weaken a nonreference
2198
2199(F) You attempted to weaken something that was not a reference. Only
2200references can be weakened.
2201
2202=item Character class [:%s:] unknown
2203
2204(F) The class in the character class [: :] syntax is unknown.
437784d6 2205See L<perlre>.
a99ba403
GS
2206
2207=item Character class syntax [%s] belongs inside character classes
2208
ddda08b7 2209(W unsafe) The character class constructs [: :], [= =], and [. .] go
a99ba403 2210I<inside> character classes, the [] are part of the construct,
437784d6
GS
2211for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2212are not currently implemented; they are simply placeholders for
2213future extensions.
a99ba403
GS
2214
2215=item Constant is not %s reference
2216
2217(F) A constant value (perhaps declared using the C<use constant> pragma)
2218is being dereferenced, but it amounts to the wrong type of reference. The
2219message indicates the type of reference that was expected. This usually
2220indicates a syntax error in dereferencing the constant value.
2221See L<perlsub/"Constant Functions"> and L<constant>.
2222
a99ba403
GS
2223=item constant(%s): %s
2224
f0af216f
GS
2225(F) The parser found inconsistencies either while attempting to define an
2226overloaded constant, or when trying to find the character name specified
2227in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
2228C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
a99ba403 2229
6798c92b
GS
2230=item CORE::%s is not a keyword
2231
2232(F) The CORE:: namespace is reserved for Perl keywords.
2233
a99ba403
GS
2234=item defined(@array) is deprecated
2235
2236(D) defined() is not usually useful on arrays because it checks for an
2237undefined I<scalar> value. If you want to see if the array is empty,
2238just use C<if (@array) { # not empty }> for example.
2239
2240=item defined(%hash) is deprecated
2241
2242(D) defined() is not usually useful on hashes because it checks for an
2243undefined I<scalar> value. If you want to see if the hash is empty,
2244just use C<if (%hash) { # not empty }> for example.
2245
2246=item Did not produce a valid header
2247
2248See Server error.
2249
cc507455 2250=item (Did you mean "local" instead of "our"?)
33633739 2251
ddda08b7 2252(W misc) Remember that "our" does not localize the declared global variable.
33633739
GS
2253You have declared it again in the same lexical scope, which seems superfluous.
2254
a99ba403
GS
2255=item Document contains no data
2256
2257See Server error.
2258
2259=item entering effective %s failed
2260
2261(F) While under the C<use filetest> pragma, switching the real and
2262effective uids or gids failed.
6b121555 2263
73b437c8
JH
2264=item false [] range "%s" in regexp
2265
ddda08b7 2266(W regexp) A character class range must start and end at a literal character, not
73b437c8
JH
2267another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2268range is interpreted as a literal "-". Consider quoting the "-", "\-".
2269See L<perlre>.
2270
af8c498a 2271=item Filehandle %s opened only for output
6b121555 2272
ddda08b7 2273(W io) You tried to read from a filehandle opened only for writing. If you
437784d6 2274intended it to be a read/write filehandle, you needed to open it with
c47ff5f1
GS
2275"+<" or "+>" or "+>>" instead of with "<" or nothing. If
2276you intended only to read from the file, use "<". See
af8c498a 2277L<perlfunc/open>.
e02fdbd2 2278
56e90b21
GS
2279=item flock() on closed filehandle %s
2280
ddda08b7 2281(W closed) The filehandle you're attempting to flock() got itself closed some
56e90b21
GS
2282time before now. Check your logic flow. flock() operates on filehandles.
2283Are you attempting to call flock() on a dirhandle by the same name?
2284
2285=item Global symbol "%s" requires explicit package name
2286
2287(F) You've said "use strict vars", which indicates that all variables
2288must either be lexically scoped (using "my"), declared beforehand using
2289"our", or explicitly qualified to say which package the global variable
2290is in (using "::").
2291
a99ba403
GS
2292=item Hexadecimal number > 0xffffffff non-portable
2293
ddda08b7 2294(W portable) The hexadecimal number you specified is larger than 2**32-1
a99ba403
GS
2295(4294967295) and therefore non-portable between systems. See
2296L<perlport> for more on portability concerns.
2297
2298=item Ill-formed CRTL environ value "%s"
2299
ddda08b7 2300(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
a99ba403
GS
2301environ array, and encountered an element without the C<=> delimiter
2302used to spearate keys from values. The element is ignored.
2303
2304=item Ill-formed message in prime_env_iter: |%s|
2305
ddda08b7 2306(W internal) A warning peculiar to VMS. Perl tried to read a logical name
a99ba403
GS
2307or CLI symbol definition when preparing to iterate over %ENV, and
2308didn't see the expected delimiter between key and value, so the
2309line was ignored.
2310
2311=item Illegal binary digit %s
2312
437784d6 2313(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
2314
2315=item Illegal binary digit %s ignored
2316
ddda08b7 2317(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
a99ba403
GS
2318Interpretation of the binary number stopped before the offending digit.
2319
2320=item Illegal number of bits in vec
2321
2322(F) The number of bits in vec() (the third argument) must be a power of
2323two from 1 to 32 (or 64, if your platform supports that).
2324
2325=item Integer overflow in %s number
2326
ddda08b7 2327(W overflow) The hexadecimal, octal or binary number you have specified either
c6edd1b7 2328as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
2329architecture, and has been converted to a floating point number. On a
233032-bit architecture the largest hexadecimal, octal or binary number
2331representable without overflow is 0xFFFFFFFF, 037777777777, or
23320b11111111111111111111111111111111 respectively. Note that Perl
2333transparently promotes all numbers to a floating point representation
2334internally--subject to loss of precision errors in subsequent
2335operations.
2336
09bef843
SB
2337=item Invalid %s attribute: %s
2338
2339The indicated attribute for a subroutine or variable was not recognized
2340by Perl or by a user-supplied handler. See L<attributes>.
2341
2342=item Invalid %s attributes: %s
2343
2344The indicated attributes for a subroutine or variable were not recognized
2345by Perl or by a user-supplied handler. See L<attributes>.
2346
73b437c8
JH
2347=item invalid [] range "%s" in regexp
2348
2349The offending range is now explicitly displayed.
2350
09bef843
SB
2351=item Invalid separator character %s in attribute list
2352
0120eecf 2353(F) Something other than a colon or whitespace was seen between the
09bef843
SB
2354elements of an attribute list. If the previous attribute
2355had a parenthesised parameter list, perhaps that list was terminated
2356too soon. See L<attributes>.
2357
a99ba403
GS
2358=item Invalid separator character %s in subroutine attribute list
2359
0120eecf 2360(F) Something other than a colon or whitespace was seen between the
a99ba403
GS
2361elements of a subroutine attribute list. If the previous attribute
2362had a parenthesised parameter list, perhaps that list was terminated
2363too soon.
2364
2365=item leaving effective %s failed
2366
2367(F) While under the C<use filetest> pragma, switching the real and
2368effective uids or gids failed.
2369
2370=item Lvalue subs returning %s not implemented yet
2371
2372(F) Due to limitations in the current implementation, array and hash
2373values cannot be returned in subroutines used in lvalue context.
2374See L<perlsub/"Lvalue subroutines">.
2375
2376=item Method %s not permitted
2377
2378See Server error.
2379
2380=item Missing %sbrace%s on \N{}
2381
2382(F) Wrong syntax of character name literal C<\N{charname}> within
2383double-quotish context.
2384
06eaf0bc
GS
2385=item Missing command in piped open
2386
ddda08b7 2387(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
06eaf0bc
GS
2388construction, but the command was missing or blank.
2389
09bef843
SB
2390=item Missing name in "my sub"
2391
2392(F) The reserved syntax for lexically scoped subroutines requires that they
2393have a name with which they can be found.
2394
56e90b21
GS
2395=item No %s specified for -%c
2396
2397(F) The indicated command line switch needs a mandatory argument, but
2398you haven't specified one.
2399
2400=item No package name allowed for variable %s in "our"
2401
2402(F) Fully qualified variable names are not allowed in "our" declarations,
2403because that doesn't make much sense under existing semantics. Such
2404syntax is reserved for future extensions.
2405
2406=item No space allowed after -%c
2407
2408(F) The argument to the indicated command line switch must follow immediately
2409after the switch, without intervening spaces.
2410
a99ba403
GS
2411=item no UTC offset information; assuming local time is UTC
2412
2413(S) A warning peculiar to VMS. Perl was unable to find the local
2414timezone offset, so it's assuming that local system time is equivalent
2415to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2416to translate to the number of seconds which need to be added to UTC to
2417get local time.
2418
2419=item Octal number > 037777777777 non-portable
2420
ddda08b7 2421(W portable) The octal number you specified is larger than 2**32-1 (4294967295)
a99ba403
GS
2422and therefore non-portable between systems. See L<perlport> for more
2423on portability concerns.
2424
2425See also L<perlport> for writing portable code.
2426
2427=item panic: del_backref
2428
2429(P) Failed an internal consistency check while trying to reset a weak
2430reference.
2431
2432=item panic: kid popen errno read
2433
2434(F) forked child returned an incomprehensible message about its errno.
2435
2436=item panic: magic_killbackrefs
2437
2438(P) Failed an internal consistency check while trying to reset all weak
2439references to an object.
2440
56e90b21
GS
2441=item Parentheses missing around "%s" list
2442
ddda08b7 2443(W parenthesis) You said something like
56e90b21
GS
2444
2445 my $foo, $bar = @_;
2446
2447when you meant
2448
2449 my ($foo, $bar) = @_;
2450
54884818 2451Remember that "my", "our", and "local" bind tighter than comma.
56e90b21 2452
a99ba403
GS
2453=item Possible Y2K bug: %s
2454
ddda08b7 2455(W y2k) You are concatenating the number 19 with another number, which
a99ba403
GS
2456could be a potential Year 2000 problem.
2457
8cd79558
GS
2458=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2459
ddda08b7 2460(W deprecated) You have written somehing like this:
8cd79558
GS
2461
2462 sub doit
2463 {
2464 use attrs qw(locked);
2465 }
2466
2467You should use the new declaration syntax instead.
2468
2469 sub doit : locked
2470 {
2471 ...
2472
2473The C<use attrs> pragma is now obsolete, and is only provided for
2474backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2475
2476
a99ba403
GS
2477=item Premature end of script headers
2478
2479See Server error.
2480
0b5b802d
GS
2481=item Repeat count in pack overflows
2482
2483(F) You can't specify a repeat count so large that it overflows
2484your signed integers. See L<perlfunc/pack>.
2485
2486=item Repeat count in unpack overflows
2487
2488(F) You can't specify a repeat count so large that it overflows
2489your signed integers. See L<perlfunc/unpack>.
2490
a99ba403
GS
2491=item realloc() of freed memory ignored
2492
2493(S) An internal routine called realloc() on something that had already
2494been freed.
2495
2496=item Reference is already weak
2497
ddda08b7 2498(W misc) You have attempted to weaken a reference that is already weak.
a99ba403
GS
2499Doing so has no effect.
2500
2501=item setpgrp can't take arguments
2502
2503(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2504unlike POSIX setpgid(), which takes a process ID and process group ID.
2505
2506=item Strange *+?{} on zero-length expression
2507
ddda08b7 2508(W regexp) You applied a regular expression quantifier in a place where it
a99ba403
GS
2509makes no sense, such as on a zero-width assertion.
2510Try putting the quantifier inside the assertion instead. For example,
2511the way to match "abc" provided that it is followed by three
2512repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2513
2514=item switching effective %s is not implemented
2515
2516(F) While under the C<use filetest> pragma, we cannot switch the
2517real and effective uids or gids.
2518
437784d6 2519=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
2520
2521=item This Perl can't set CRTL environ elements (%s=%s)
2522
ddda08b7 2523(W internal) Warnings peculiar to VMS. You tried to change or delete an element
a99ba403
GS
2524of the CRTL's internal environ array, but your copy of Perl wasn't
2525built with a CRTL that contained the setenv() function. You'll need to
2526rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2527L<perlvms>) so that the environ array isn't the target of the change to
2528%ENV which produced the warning.
2529
ddda08b7
GS
2530=item Too late to run %s block
2531
2532(W void) A CHECK or INIT block is being defined during run time proper,
2533when the opportunity to run them has already passed. Perhaps you are
2534loading a file with C<require> or C<do> when you should be using
2535C<use> instead. Or perhaps you should put the C<require> or C<do>
2536inside a BEGIN block.
2537
a99ba403
GS
2538=item Unknown open() mode '%s'
2539
437784d6 2540(F) The second argument of 3-argument open() is not among the list
c47ff5f1
GS
2541of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2542C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
a99ba403
GS
2543
2544=item Unknown process %x sent message to prime_env_iter: %s
2545
2546(P) An error peculiar to VMS. Perl was reading values for %ENV before
2547iterating over it, and someone else stuck a message in the stream of
2548data Perl expected. Someone's very confused, or perhaps trying to
2549subvert Perl's population of %ENV for nefarious purposes.
2550
af8c498a
GS
2551=item Unrecognized escape \\%c passed through
2552
ddda08b7 2553(W misc) You used a backslash-character combination which is not recognized
1028017a 2554by Perl. The character was understood literally.
af8c498a 2555
09bef843
SB
2556=item Unterminated attribute parameter in attribute list
2557
2558(F) The lexer saw an opening (left) parenthesis character while parsing an
2559attribute list, but the matching closing (right) parenthesis
2560character was not found. You may need to add (or remove) a backslash
2561character to get your parentheses to balance. See L<attributes>.
2562
2563=item Unterminated attribute list
2564
2565(F) The lexer found something other than a simple identifier at the start
2566of an attribute, and it wasn't a semicolon or the start of a
2567block. Perhaps you terminated the parameter list of the previous attribute
2568too soon. See L<attributes>.
2569
09bef843
SB
2570=item Unterminated attribute parameter in subroutine attribute list
2571
2572(F) The lexer saw an opening (left) parenthesis character while parsing a
2573subroutine attribute list, but the matching closing (right) parenthesis
2574character was not found. You may need to add (or remove) a backslash
2575character to get your parentheses to balance.
2576
2577=item Unterminated subroutine attribute list
2578
2579(F) The lexer found something other than a simple identifier at the start
2580of a subroutine attribute, and it wasn't a semicolon or the start of a
2581block. Perhaps you terminated the parameter list of the previous attribute
2582too soon.
2583
a99ba403 2584=item Value of CLI symbol "%s" too long
eb6e2d6f 2585
ddda08b7 2586(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
a99ba403
GS
2587element from a CLI symbol table, and found a resultant string longer
2588than 1024 characters. The return value has been truncated to 1024
2589characters.
eb6e2d6f 2590
a99ba403 2591=item Version number must be a constant number
ba8251e8 2592
a99ba403
GS
2593(P) The attempt to translate a C<use Module n.n LIST> statement into
2594its equivalent C<BEGIN> block found an internal inconsistency with
2595the version number.
2596
2597=back
27806c82 2598
a5222a85 2599=head1 Obsolete Diagnostics
3175b8cd 2600
a99ba403
GS
2601=over 4
2602
2603=item Character class syntax [: :] is reserved for future extensions
2604
2605(W) Within regular expression character classes ([]) the syntax beginning
2606with "[:" and ending with ":]" is reserved for future extensions.
2607If you need to represent those character sequences inside a regular
2608expression character class, just quote the square brackets with the
2609backslash: "\[:" and ":\]".
2610
2611=item Ill-formed logical name |%s| in prime_env_iter
2612
2613(W) A warning peculiar to VMS. A logical name was encountered when preparing
2614to iterate over %ENV which violates the syntactic rules governing logical
2615names. Because it cannot be translated normally, it is skipped, and will not
2616appear in %ENV. This may be a benign occurrence, as some software packages
2617might directly modify logical name tables and introduce nonstandard names,
2618or it may indicate that a logical name table has been corrupted.
2619
34d09196
GS
2620=item Probable precedence problem on %s
2621
2622(W) The compiler found a bareword where it expected a conditional,
2623which often indicates that an || or && was parsed as part of the
2624last argument of the previous construct, for example:
2625
2626 open FOO || die;
2627
a99ba403
GS
2628=item regexp too big
2629
2630(F) The current implementation of regular expressions uses shorts as
2631address offsets within a string. Unfortunately this means that if
2632the regular expression compiles to longer than 32767, it'll blow up.
2633Usually when you want a regular expression this big, there is a better
2634way to do it with multiple statements. See L<perlre>.
2635
2636=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2637
2638(D) Perl versions before 5.004 misinterpreted any type marker followed
2639by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2640"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2641
2642However, the developers of Perl 5.004 could not fix this bug completely,
2643because at least two widely-used modules depend on the old meaning of
2644"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2645old (broken) way inside strings; but it generates this message as a
2646warning. And in Perl 5.005, this special treatment will cease.
2647
2648=back
3175b8cd 2649
fc641c2d
JH
2650=head1 Known Problems
2651
227e8dd4 2652=head2 Thread test failures
fc641c2d 2653
227e8dd4
GS
2654The subtests 19 and 20 of lib/thread.t test are known to fail due to
2655fundamental problems in the 5.005 threading implementation. These are
2656not new failures--Perl 5.005_0x has the same bugs, but didn't have these
2657tests.
fc641c2d
JH
2658
2659=head2 EBCDIC platforms not supported
2660
227e8dd4
GS
2661In earlier releases of Perl, EBCDIC environments like OS390 (also
2662known as Open Edition MVS) and VM-ESA were supported. Due to changes
2663required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
2664supported in Perl 5.6.0.
fc641c2d 2665
d57b1ce7
GS
2666=head2 In 64-bit HP-UX the lib/io_multihomed test may hang
2667
2668The lib/io_multihomed test may hang in HP-UX if Perl has been
2669configured to be 64-bit. Because other 64-bit platforms do not
2670hang in this test, HP-UX is suspect. All other tests pass
2671in 64-bit HP-UX. The test attempts to create and connect to
2672"multihomed" sockets (sockets which have multiple IP addresses).
2673
f46deeb4
JH
2674=head2 NEXTSTEP 3.3 POSIX test failure
2675
2676In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
2677operating system libraries is buggy: the %j format numbers the days of
2678a month starting from zero, which, while being logical to programmers,
2679will cause the subtests 19 to 27 of the lib/posix test may fail.
2680
2cae8c0d
JH
2681=head2 Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc
2682
2683If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
2684The cure is to use the vendor cc, it comes with the operating system
2685and produces good code.
2686
fc641c2d
JH
2687=head2 UNICOS/mk CC failures during Configure run
2688
2689In UNICOS/mk the following errors may appear during the Configure run:
2690
2691 Guessing which symbols your C compiler and preprocessor define...
2692 CC-20 cc: ERROR File = try.c, Line = 3
2693 ...
2694 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
2695 ...
2696 4 errors detected in the compilation of "try.c".
2697
2698The culprit is the broken awk of UNICOS/mk. The effect is fortunately
2699rather mild: Perl itself is not adversely affected by the error, only
2700the h2ph utility coming with Perl, and that is rather rarely needed
2701these days.
2702
14190b26
GS
2703=head2 Arrow operator and arrays
2704
2705When the left argument to the arrow operator C<< -> >> is an array, or
2706the C<scalar> operator operating on an array, the result of the
2707operation must be considered erroneous. For example:
2708
2709 @x->[2]
2710 scalar(@x)->[2]
2711
2712These expressions will get run-time errors in some future release of
2713Perl.
2714
fc641c2d
JH
2715=head2 Many features still experimental
2716
227e8dd4
GS
2717As discussed above, many features are still experimental. Interfaces and
2718implementation of these features are subject to change, and in extreme cases,
2719even subject to removal in some future release of Perl. These features
2720include the following:
fc641c2d
JH
2721
2722=over 4
2723
2724=item Threads
2725
2726=item Unicode
2727
2728=item Lvalue subroutines
2729
2730=item Weak references
2731
2732=item File globbing now implemented internally
2733
2734=item The Compiler suite
2735
227e8dd4 2736=item The DB module
fc641c2d 2737
227e8dd4 2738=item The regular expression constructs C<(?{ code })> and C<(??{ code })>
fc641c2d
JH
2739
2740=back
2741
ba8251e8
GS
2742=head1 BUGS
2743
437784d6 2744If you find what you think is a bug, you might check the
14218588 2745articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
GS
2746There may also be information at http://www.perl.com/perl/, the Perl
2747Home Page.
2748
2749If you believe you have an unreported bug, please run the B<perlbug>
642f9deb 2750program included with your release. Be sure to trim your bug down
ba8251e8 2751to a tiny but sufficient test case. Your bug report, along with the
14218588 2752output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
GS
2753analysed by the Perl porting team.
2754
2755=head1 SEE ALSO
2756
2757The F<Changes> file for exhaustive details on what changed.
2758
2759The F<INSTALL> file for how to build Perl.
2760
2761The F<README> file for general stuff.
2762
2763The F<Artistic> and F<Copying> files for copyright information.
2764
2765=head1 HISTORY
2766
a5222a85
GS
2767Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2768contributions from The Perl Porters.
ba8251e8
GS
2769
2770Send omissions or corrections to <F<perlbug@perl.com>>.
2771
2772=cut