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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
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209=back
210
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211=head2 C Source Incompatibilities
212
213=over 4
214
215=item C<PERL_POLLUTE>
216
217Release 5.005 grandfathered old global symbol names by providing preprocessor
642f9deb 218macros for extension source compatibility. As of release 5.6.0, these
e02fdbd2 219preprocessor definitions are not available by default. You need to explicitly
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220compile perl with C<-DPERL_POLLUTE> to get these definitions. For
221extensions still using the old symbols, this option can be
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222specified via MakeMaker:
223
14218588 224 perl Makefile.PL POLLUTE=1
e02fdbd2 225
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226=item C<PERL_IMPLICIT_CONTEXT>
227
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228 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
229 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
230 intended to be enabled by users at this time.
af365420 231
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232This new build option provides a set of macros for all API functions
233such that an implicit interpreter/thread context argument is passed to
234every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 235amounts to a macro invocation that actually translates to something like
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236C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
237to not have any significant source compatibility issues, the difference
238between a macro and a real function call will need to be considered.
239
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240This means that there B<is> a source compatibility issue as a result of
241this if your extensions attempt to use pointers to any of the Perl API
242functions.
243
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244Note that the above issue is not relevant to the default build of
245Perl, whose interfaces continue to match those of prior versions
246(but subject to the other options described here).
247
2c2d71f5 248See L<perlguts/"The Perl API"> for detailed information on the
642f9deb 249ramifications of building Perl with this option.
2c2d71f5 250
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251=item C<PERL_POLLUTE_MALLOC>
252
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253Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
254the system's malloc family of functions to be usurped by the Perl versions,
255since by default they used the same names. Besides causing problems on
256platforms that do not allow these functions to be cleanly replaced, this
257also meant that the system versions could not be called in programs that
258used Perl's malloc. Previous versions of Perl have allowed this behaviour
259to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
260definitions.
86058a2d 261
642f9deb 262As of release 5.6.0, Perl's malloc family of functions have default names
86058a2d 263distinct from the system versions. You need to explicitly compile perl with
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264C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
265and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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266the default.
267
268Note that these functions do B<not> constitute Perl's memory allocation API.
269See L<perlguts/"Memory Allocation"> for further information about that.
270
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271=back
272
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273=head2 Compatible C Source API Changes
274
275=over
276
277=item C<PATCHLEVEL> is now C<PERL_VERSION>
278
14218588 279The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 280are now available by default from perl.h, and reflect the base revision,
14218588 281patchlevel, and subversion respectively. C<PERL_REVISION> had no
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282prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
283previously available as C<PATCHLEVEL> and C<SUBVERSION>.
284
14218588 285The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 286the numbers have come to stand for in common practice. For compatibility,
14218588 287the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 288included (as required before), so there is no source incompatibility
14218588 289from the change.
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290
291=back
292
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293=head2 Binary Incompatibilities
294
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295In general, the default build of this release is expected to be binary
296compatible for extensions built with the 5.005 release or its maintenance
297versions. However, specific platforms may have broken binary compatibility
298due to changes in the defaults used in hints files. Therefore, please be
299sure to always check the platform-specific README files for any notes to
300the contrary.
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301
302The usethreads or usemultiplicity builds are B<not> binary compatible
303with the corresponding builds in 5.005.
e02fdbd2 304
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305On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
306among others), purely internal symbols such as parser functions and the
307run time opcodes are not exported by default. Perl 5.005 used to export
308all functions irrespective of whether they were considered part of the
309public API or not.
310
311For the full list of public API functions, see L<perlapi>.
312
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313=head1 Installation and Configuration Improvements
314
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315=head2 -Dusethreads means something different
316
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317 WARNING: Support for threads continues to be an experimental feature.
318 Interfaces and implementation are subject to sudden and drastic changes.
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319
320The -Dusethreads flag now enables the experimental interpreter-based thread
321support by default. To get the flavor of experimental threads that was in
ba869deb 3225.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
16070b82 323
642f9deb 324As of v5.6.0, interpreter-threads support is still lacking a way to
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325create new threads from Perl (i.e., C<use Thread;> will not work with
326interpreter threads). C<use Thread;> continues to be available when you
642f9deb 327specify the -Duse5005threads option to Configure, bugs and all.
16070b82 328
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329=head2 New Configure flags
330
331The following new flags may be enabled on the Configure command line
332by running Configure with C<-Dflag>.
333
334 usemultiplicity
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335 usethreads useithreads (new interpreter threads: no Perl API yet)
336 usethreads use5005threads (threads as they were in 5.005)
67d3893f 337
ba869deb 338 use64bitint (equal to now deprecated 'use64bits')
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339 use64bitall
340
67d3893f 341 uselongdouble
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342 usemorebits
343 uselargefiles
ba869deb 344 usesocks (only SOCKS v5 supported)
a5222a85 345
10cc9d2a 346=head2 Threadedness and 64-bitness now more daring
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347
348The Configure options enabling the use of threads and the use of
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34964-bitness are now more daring in the sense that they no more have an
350explicit list of operating systems of known threads/64-bit
67d3893f 351capabilities. In other words: if your operating system has the
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352necessary APIs and datatypes, you should be able just to go ahead and
353use them, for threads by Configure -Dusethreads, and for 64 bits
10cc9d2a 354either explicitly by Configure -Duse64bitint or implicitly if your
642f9deb 355system has 64-bit wide datatypes. See also L<"64-bit support">.
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356
357=head2 Long Doubles
358
359Some platforms have "long doubles", floating point numbers of even
437784d6 360larger range than ordinary "doubles". To enable using long doubles for
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361Perl's scalars, use -Duselongdouble.
362
363=head2 -Dusemorebits
364
642f9deb 365You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
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366See also L<"64-bit support">.
367
368=head2 -Duselargefiles
369
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370Some platforms support system APIs that are capable of handling large files
371(typically, files larger than two gigabytes). Perl will try to use these
372APIs if you ask for -Duselargefiles.
373
67d3893f 374See L<"Large file support"> for more information.
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375
376=head2 installusrbinperl
377
378You can use "Configure -Uinstallusrbinperl" which causes installperl
379to skip installing perl also as /usr/bin/perl. This is useful if you
380prefer not to modify /usr/bin for some reason or another but harmful
381because many scripts assume to find Perl in /usr/bin/perl.
382
383=head2 SOCKS support
384
385You can use "Configure -Dusesocks" which causes Perl to probe
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386for the SOCKS proxy protocol library (v5, not v4). For more information
387on SOCKS, see:
388
389 http://www.socks.nec.com/
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390
391=head2 C<-A> flag
392
393You can "post-edit" the Configure variables using the Configure C<-A>
642f9deb 394switch. The editing happens immediately after the platform specific
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395hints files have been processed but before the actual configuration
396process starts. Run C<Configure -h> to find out the full C<-A> syntax.
397
c35dd67d 398=head2 Enhanced Installation Directories
67d3893f 399
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400The installation structure has been enriched to improve the support
401for maintaining multiple versions of perl, to provide locations for
402vendor-supplied modules, scripts, and manpages, and to ease maintenance
403of locally-added modules, scripts, and manpages. See the section on
404Installation Directories in the INSTALL file for complete details.
405For most users building and installing from source, the defaults should
406be fine.
407
408If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
409special values for library directories, you might wish to consider using
410the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
411config.sh file from an earlier version of perl, you should be sure to
412check that Configure makes sensible choices for the new directories.
413See INSTALL for complete details.
67d3893f 414
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415=head1 Core Changes
416
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417=head2 Unicode and UTF-8 support
418
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419 WARNING: This is an experimental feature. Implementation details are
420 subject to change.
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421
422Perl now uses UTF-8 as its internal representation for character
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423strings. The C<utf8> and C<bytes> pragmas are used to control this support
424in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
393fec97 425more information.
9d73390d 426
16070b82 427=head2 Interpreter cloning, threads, and concurrency
af365420 428
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429 WARNING: This is an experimental feature. Implementation details are
430 subject to change.
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431
432Perl 5.005_63 introduces the beginnings of support for running multiple
433interpreters concurrently in different threads. In conjunction with
434the perl_clone() API call, which can be used to selectively duplicate
435the state of any given interpreter, it is possible to compile a
436piece of code once in an interpreter, clone that interpreter
437one or more times, and run all the resulting interpreters in distinct
438threads.
439
440On Windows, this feature is used to emulate fork() at the interpreter
441level. See L<perlfork>.
442
443This feature is still in evolution. It is eventually meant to be used
444to selectively clone a subroutine and data reachable from that
445subroutine in a separate interpreter and run the cloned subroutine
446in a separate thread. Since there is no shared data between the
447interpreters, little or no locking will be needed (unless parts of
448the symbol table are explicitly shared). This is obviously intended
449to be an easy-to-use replacement for the existing threads support.
450
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451Support for cloning interpreters and interpreter concurrency can be
452enabled using the -Dusethreads Configure option (see win32/Makefile for
453how to enable it on Windows.) The resulting perl executable will be
454functionally identical to one that was built with -Dmultiplicity, but
455the perl_clone() API call will only be available in the former.
af365420 456
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457-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
458enables Perl source code changes that provide a clear separation between
459the op tree and the data it operates with. The former is immutable, and
460can therefore be shared between an interpreter and all of its clones,
461while the latter is considered local to each interpreter, and is therefore
462copied for each clone.
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463
464Note that building Perl with the -Dusemultiplicity Configure option
465is adequate if you wish to run multiple B<independent> interpreters
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466concurrently in different threads. -Dusethreads only provides the
467additional functionality of the perl_clone() API call and other
468support for running B<cloned> interpreters concurrently.
af365420 469
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470=head2 Lexically scoped warning categories
471
472You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 473level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 474for details.
9d73390d 475
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476=head2 Lvalue subroutines
477
642f9deb 478 WARNING: This is an experimental feature. Details are subject to change.
a5222a85 479
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480Subroutines can now return modifiable lvalues.
481See L<perlsub/"Lvalue subroutines">.
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482
483=head2 "our" declarations
484
485An "our" declaration introduces a value that can be best understood
486as a lexically scoped symbolic alias to a global variable in the
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487package that was current where the variable was declared. This is
488mostly useful as an alternative to the C<vars> pragma, but also provides
489the opportunity to introduce typing and other attributes for such
490variables. See L<perlfunc/our>.
491
44dcb63b 492=head2 Support for strings represented as a vector of ordinals
16070b82 493
dd629d5b 494Literals of the form C<v1.2.3.4> are now parsed as a string composed of
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495of characters with the specified ordinals. This is an alternative, more
496readable way to construct (possibly unicode) strings instead of
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497interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
498C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
499parsed the same as C<v1.2.3>.
16070b82 500
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501Strings written in this form are also useful to represent version "numbers".
502It is easy to compare such version "numbers" (which are really just plain
503strings) using any of the usual string comparison operators C<eq>, C<ne>,
504C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
505C<&>, etc.
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506
507In conjunction with the new C<$^V> magic variable (which contains
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508the perl version as a string), such literals can be used as a readable way
509to check if you're running a particular version of Perl:
16070b82 510
44dcb63b 511 # this will parse in older versions of Perl also
642f9deb 512 if ($^V and $^V gt v5.6.0) {
44dcb63b 513 # new features supported
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514 }
515
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516C<require> and C<use> also have some special magic to support such literals.
517They will be interpreted as a version rather than as a module name:
16070b82 518
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519 require v5.6.0; # croak if $^V lt v5.6.0
520 use v5.6.0; # same, but croaks at compile-time
a5222a85 521
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522Alternatively, the C<v> may be omitted if there is more than one dot:
523
524 require 5.6.0;
525 use 5.6.0;
526
44dcb63b 527Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
b22c7a20 528to print ordinals of characters in arbitrary strings:
1761cee5 529
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GS
530 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
531 printf "%*vX", ":", $addr; # formats IPv6 address
dd629d5b 532 printf "%*vb", " ", $bits; # displays bitstring
1761cee5 533
191d61a7 534See L<perldata/"Scalar value constructors"> for additional information.
44dcb63b 535
a5222a85
GS
536=head2 Weak references
537
642f9deb 538 WARNING: This is an experimental feature.
a5222a85 539
d4629d6a
GS
540In previous versions of Perl, you couldn't cache objects so as
541to allow them to be deleted if the last reference from outside
542the cache is deleted. The reference in the cache would hold a
543reference count on the object and the objects would never be
544destroyed.
545
546Another familiar problem is with circular references. When an
547object references itself, its reference count would never go
548down to zero, and it would not get destroyed until the program
549is about to exit.
550
551Weak references solve this by allowing you to "weaken" any
552reference, that is, make it not count towards the reference count.
553When the last non-weak reference to an object is deleted, the object
554is destroyed and all the weak references to the object are
555automatically undef-ed.
a5222a85 556
d4629d6a
GS
557To use this feature, you need the WeakRef package from CPAN, which
558contains additional documentation.
559
becf2bd3
GS
560=head2 File globbing implemented internally
561
642f9deb
GS
562 WARNING: This is currently an experimental feature. Interfaces and
563 implementation are likely to change.
becf2bd3 564
52bb0670
GS
565Perl now uses the File::Glob implementation of the glob() operator
566automatically. This avoids using an external csh process and the
567problems associated with it.
becf2bd3 568
5fdc711f
GS
569=head2 Binary numbers supported
570
4f19785b
WSI
571Binary numbers are now supported as literals, in s?printf formats, and
572C<oct()>:
573
14218588
GS
574 $answer = 0b101010;
575 printf "The answer is: %b\n", oct("0b101010");
4f19785b 576
a5222a85
GS
577=head2 Some arrows may be omitted in calls through references
578
579Perl now allows the arrow to be omitted in many constructs
580involving subroutine calls through references. For example,
c47ff5f1 581C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
a5222a85 582This is rather similar to how the arrow may be omitted from
c47ff5f1
GS
583C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
584required for C<< foo(10)->('bar') >>.
a5222a85 585
afebc493
GS
586=head2 exists() is supported on subroutine names
587
588The exists() builtin now works on subroutine names. A subroutine
589is considered to exist if it has been declared (even if implicitly).
590See L<perlfunc/exists> for examples.
591
01020589
GS
592=head2 exists() and delete() are supported on array elements
593
594The exists() and delete() builtins now work on simple arrays as well.
595The behavior is similar to that on hash elements.
596
8ea97a1e 597exists() can be used to check whether an array element has been
8216c1fd
GS
598initialized. This avoids autovivifying array elements that don't exist.
599If the array is tied, the EXISTS() method in the corresponding tied
600package will be invoked.
8ea97a1e
GS
601
602delete() may be used to remove an element from the array and return
603it. The array element at that position returns to its unintialized
604state, so that testing for the same element with exists() will return
605false. If the element happens to be the one at the end, the size of
8216c1fd
GS
606the array also shrinks up to the highest element that tests true for
607exists(), or 0 if none such is found. If the array is tied, the DELETE()
608method in the corresponding tied package will be invoked.
01020589
GS
609
610See L<perlfunc/exists> and L<perlfunc/delete> for examples.
611
5fdc711f
GS
612=head2 syswrite() ease-of-use
613
a5222a85
GS
614The length argument of C<syswrite()> has become optional.
615
b1a9ed4a 616=head2 File and directory handles can be autovivified
a5222a85 617
c47ff5f1 618Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
b1a9ed4a
GS
619handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
620socket(), and accept()) now autovivify a file or directory handle
621if the handle passed to them is an uninitialized scalar variable. This
622allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
623to be used to create filehandles that will conveniently be closed
624automatically when the scope ends, provided there are no other references
625to them. This largely eliminates the need for typeglobs when opening
626filehandles that must be passed around, as in the following example:
a5222a85
GS
627
628 sub myopen {
629 open my $fh, "@_"
630 or die "Can't open '@_': $!";
631 return $fh;
632 }
633
634 {
635 my $f = myopen("</etc/motd");
636 print <$f>;
637 # $f implicitly closed here
638 }
639
642f9deb
GS
640=head2 open() with more than two arguments
641
642If open() is passed three arguments instead of two, the second arguments
643is used as the mode and the third argument is taken to be the file name.
644This is primarily useful for protecting against unintended magic behavior
645of the traditional two-argument form. See L<perlfunc/open>.
6c67e1bb 646
5fdc711f
GS
647=head2 64-bit support
648
642f9deb
GS
649 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
650 deprecated. Use -Duse64bitint instead.
10cc9d2a 651
55f6b6ec
JH
652Any platform that has 64-bit integers either
653
654 (1) natively as longs or ints
655 (2) via special compiler flags
656 (3) using long long or int64_t
657
658are able to use "quads" (64-bit integers) as follows:
9c107f78
JH
659
660=over 4
661
a5222a85
GS
662=item *
663
664constants (decimal, hexadecimal, octal, binary) in the code
665
666=item *
9c107f78 667
a5222a85 668arguments to oct() and hex()
9c107f78 669
a5222a85
GS
670=item *
671
672arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
673
674=item *
9c107f78 675
a5222a85 676printed as such
9c107f78 677
a5222a85
GS
678=item *
679
680pack() and unpack() "q" and "Q" formats
681
682=item *
683
972b05a9
JH
684in basic arithmetics: + - * / % (NOTE: operating close to the limits
685of the integer values may produce surprising results)
a5222a85
GS
686
687=item *
1fad5d67 688
972b05a9 689in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
642f9deb 690to be 32 bits wide but now operate on the full native width.)
972b05a9
JH
691
692=item *
693
694vec()
9c107f78
JH
695
696=back
697
698Note that unless you have the case (a) you will have to configure
10cc9d2a 699and compile Perl using the -Duse64bitint Configure flag.
9c107f78 700
49c10eea 701There are actually two modes of 64-bitness: the first one is achieved
10cc9d2a
JH
702using Configure -Duse64bitint and the second one using Configure
703-Duse64bitall. The difference is that the first one is minimal and
55f6b6ec
JH
704the second one maximal.
705
706The C<use64bitint> does only as much as is required to get 64-bit
707integers into Perl (this may mean, for example, using "long longs")
708while your memory may still be limited to 2 gigabytes (because your
709pointers could still be 32-bit). Note that the name C<64bitint> does
710not imply that your C compiler will be using 64-bit C<int>s (it might,
711but it doesn't have to): the C<use64bitint> means that you will be
712able to have 64 bits wide scalar values.
713
714The C<use64bitall> goes all the way by attempting to switch also
715integers (if it can), longs (and pointers) to being 64-bit. This may
716create an even more binary incompatible Perl than -Duse64bitint: the
717resulting executable may not run at all in a 32-bit box, or you may
718have to reboot/reconfigure/rebuild your operating system to be 64-bit
719aware.
49c10eea 720
10cc9d2a
JH
721Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
722nor -Duse64bitall.
49c10eea 723
2d4389e4 724Last but not least: note that due to Perl's habit of always using
07447971 725floating point numbers, the quads are still not true integers.
d0ba1bd2
JH
726When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
727-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
728are silently promoted to floating point numbers, after which they will
642f9deb 729start losing precision (in their lower digits).
2d4389e4
JH
730
731=head2 Large file support
732
733If you have filesystems that support "large files" (files larger than
aa855319 7342 gigabytes), you may now also be able to create and access them from
55f6b6ec
JH
735Perl. NOTE: the default action is to use the large file support, if
736available on the platform.
737
738If the large file support is on, and you have a Fcntl constant
739O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
740of sysopen().
741
742Beware: unless your filesystem also supports "sparse files" seeking to
743umpteen petabytes may be unadvisable.
2d4389e4 744
eed7fde4
JH
745Note that in addition to requiring a proper file system to do large
746files you may also need to adjust your per-process (or your
747per-system, or per-process-group, or per-user-group) maximum filesize
748limits before running Perl scripts that try to handle large files,
749especially if you intend to write such files.
750
751Finally, in addition to your process/process group maximum filesize
752limits, you may have quota limits on your filesystems that stop you
753(your user id or your user group id) from using large files.
754
755Adjusting your process/user/group/file system/operating system limits
756is outside the scope of Perl core language. For process limits, you
757may try increasing the limits using your shell's limits/limit/ulimit
758command before running Perl. The BSD::Resource extension (not
759included with the standard Perl distribution) may also be of use, it
760offers the getrlimit/setrlimit interface that can be used to adjust
761process resource usage limits, including the maximum filesize limit.
475d79b5 762
aa855319
JH
763=head2 Long doubles
764
765In some systems you may be able to use long doubles to enhance the
822ba51d 766range and precision of your double precision floating point numbers
aa855319
JH
767(that is, Perl's numbers). Use Configure -Duselongdouble to enable
768this support (if it is available).
769
770=head2 "more bits"
771
822ba51d 772You can "Configure -Dusemorebits" to turn on both the 64-bit support
aa855319 773and the long double support.
09bef843 774
43481408
GS
775=head2 Enhanced support for sort() subroutines
776
642f9deb 777Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
43481408 778now be used as sort subroutines. In either case, the two elements to
af365420 779be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
43481408
GS
780
781For unprototyped sort subroutines, the historical behavior of passing
782the elements to be compared as the global variables $a and $b remains
783unchanged.
784
62c18ce2
GS
785=head2 Better syntax checks on parenthesized unary operators
786
787Expressions such as:
788
14218588
GS
789 print defined(&foo,&bar,&baz);
790 print uc("foo","bar","baz");
791 undef($foo,&bar);
62c18ce2 792
7711098a 793used to be accidentally allowed in earlier versions, and produced
14218588
GS
794unpredictable behaviour. Some produced ancillary warnings
795when used in this way; others silently did the wrong thing.
62c18ce2
GS
796
797The parenthesized forms of most unary operators that expect a single
14218588
GS
798argument now ensure that they are not called with more than one
799argument, making the cases shown above syntax errors. The usual
800behaviour of:
62c18ce2 801
14218588
GS
802 print defined &foo, &bar, &baz;
803 print uc "foo", "bar", "baz";
804 undef $foo, &bar;
62c18ce2
GS
805
806remains unchanged. See L<perlop>.
807
3e3318e7
GS
808=head2 POSIX character class syntax [: :] supported
809
810For example to match alphabetic characters use /[[:alpha:]]/.
811See L<perlre> for details.
812
5a929a98 813=head2 Improved C<qw//> operator
8127e0e3 814
26ef7447
GS
815The C<qw//> operator is now evaluated at compile time into a true list
816instead of being replaced with a run time call to C<split()>. This
14218588
GS
817removes the confusing misbehaviour of C<qw//> in scalar context, which
818had inherited that behaviour from split().
26ef7447
GS
819
820Thus:
821
822 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
823
824now correctly prints "3|a", instead of "2|a".
8127e0e3 825
5a929a98
VU
826=head2 pack() format 'Z' supported
827
828The new format type 'Z' is useful for packing and unpacking null-terminated
829strings. See L<perlfunc/"pack">.
830
4d0c1c44 831=head2 pack() format modifier '!' supported
ee3907e2 832
14218588 833The new format type modifier '!' is useful for packing and unpacking
ee3907e2
JH
834native shorts, ints, and longs. See L<perlfunc/"pack">.
835
f29c64d6
GS
836=head2 pack() and unpack() support counted strings
837
a5222a85 838The template character '/' can be used to specify a counted string
f29c64d6
GS
839type to be packed or unpacked. See L<perlfunc/"pack">.
840
a5222a85
GS
841=head2 Comments in pack() templates
842
843The '#' character in a template introduces a comment up to
844end of the line. This facilitates documentation of pack()
845templates.
846
2b92dfce
GS
847=head2 $^X variables may now have names longer than one character
848
849Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
850error. Now variable names that begin with a control character may be
851arbitrarily long. However, for compatibility reasons, these variables
852I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 853C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
2b92dfce
GS
854than one control character, such as C<${^XY^Z}>, are illegal.
855
14218588
GS
856The old syntax has not changed. As before, `^X' may be either a
857literal control-X character or the two-character sequence `caret' plus
858`X'. When braces are omitted, the variable name stops after the
2b92dfce 859control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 860C<$^X . "YZ"> as before.
2b92dfce
GS
861
862As before, lexical variables may not have names beginning with control
863characters. As before, variables whose names begin with a control
14218588
GS
864character are always forced to be in package `main'. All such variables
865are reserved for future extensions, except those that begin with
09bef843 866C<^_>, which may be used by user programs and are guaranteed not to
14218588 867acquire special meaning in any future version of Perl.
2b92dfce 868
09bef843
SB
869=head2 C<use attrs> implicit in subroutine attributes
870
871Formerly, if you wanted to mark a subroutine as being a method call or
872as requiring an automatic lock() when it is entered, you had to declare
873that with a C<use attrs> pragma in the body of the subroutine.
16070b82 874That can now be accomplished with declaration syntax, like this:
09bef843 875
0120eecf 876 sub mymethod : locked method ;
09bef843 877 ...
16070b82
GS
878 sub mymethod : locked method {
879 ...
880 }
881
882 sub othermethod :locked :method ;
883 ...
884 sub othermethod :locked :method {
09bef843
SB
885 ...
886 }
887
16070b82
GS
888
889(Note how only the first C<:> is mandatory, and whitespace surrounding
890the C<:> is optional.)
891
09bef843
SB
892F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
893with the stubs they provide. See L<attributes>.
894
a5222a85
GS
895=head2 Support for interpolating named characters
896
21bad921
GS
897The new C<\N> escape interpolates named characters within strings.
898For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
899with a unicode smiley face at the end.
a5222a85 900
a5222a85
GS
901=head2 C<require> and C<do> may be overridden
902
903C<require> and C<do 'file'> operations may be overridden locally
904by importing subroutines of the same name into the current package
905(or globally by importing them into the CORE::GLOBAL:: namespace).
906Overriding C<require> will also affect C<use>, provided the override
907is visible at compile-time.
908See L<perlsub/"Overriding Built-in Functions">.
909
910=head2 New variable $^C reflects C<-c> switch
911
08cd8952 912C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
913in compile-only mode (i.e. via the C<-c> switch). Since
914BEGIN blocks are executed under such conditions, this variable
915enables perl code to determine whether actions that make sense
916only during normal running are warranted. See L<perlvar>.
917
063663a9 918=head2 New variable $^V contains Perl version as a string
16070b82 919
da2094fd 920C<$^V> contains the Perl version number as a string composed of
642f9deb 921characters whose ordinals match the version numbers, i.e. v5.6.0.
063663a9 922This may be used in string comparisons.
44dcb63b
GS
923
924See C<Support for strings represented as a vector of ordinals> for an
925example.
16070b82 926
a5222a85
GS
927=head2 Optional Y2K warnings
928
929If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
930it emits optional warnings when concatenating the number 19
931with another number.
932
933This behavior must be specifically enabled when running Configure.
b4bc034f 934See F<INSTALL> and F<README.Y2K>.
a5222a85 935
fbad3eb5
GS
936=head1 Significant bug fixes
937
c47ff5f1 938=head2 <HANDLE> on empty files
fbad3eb5 939
191f2cf3 940With C<$/> set to C<undef>, "slurping" an empty file returns a string of
14218588 941zero length (instead of C<undef>, as it used to) the first time the
191f2cf3
GS
942HANDLE is read after C<$/> is set to C<undef>. Further reads yield
943C<undef>.
fbad3eb5
GS
944
945This means that the following will append "foo" to an empty file (it used
14218588 946to do nothing):
fbad3eb5
GS
947
948 perl -0777 -pi -e 's/^/foo/' empty_file
949
14218588 950The behaviour of:
fbad3eb5
GS
951
952 perl -pi -e 's/^/foo/' empty_file
953
954is unchanged (it continues to leave the file empty).
955
0244c3a4
GS
956=head2 C<eval '...'> improvements
957
958Line numbers (as reflected by caller() and most diagnostics) within
642f9deb 959C<eval '...'> were often incorrect where here documents were involved.
0244c3a4
GS
960This has been corrected.
961
962Lexical lookups for variables appearing in C<eval '...'> within
963functions that were themselves called within an C<eval '...'> were
14218588
GS
964searching the wrong place for lexicals. The lexical search now
965correctly ends at the subroutine's block boundary.
0244c3a4
GS
966
967Parsing of here documents used to be flawed when they appeared as
968the replacement expression in C<eval 's/.../.../e'>. This has
969been fixed.
970
a5222a85
GS
971=head2 All compilation errors are true errors
972
973Some "errors" encountered at compile time were by neccessity
974generated as warnings followed by eventual termination of the
975program. This enabled more such errors to be reported in a
976single run, rather than causing a hard stop at the first error
977that was encountered.
978
979The mechanism for reporting such errors has been reimplemented
980to queue compile-time errors and report them at the end of the
981compilation as true errors rather than as warnings. This fixes
08cd8952
GS
982cases where error messages leaked through in the form of warnings
983when code was compiled at run time using C<eval STRING>, and
642f9deb 984also allows such errors to be reliably trapped using C<eval "...">.
a5222a85 985
45bc9206
GS
986=head2 Automatic flushing of output buffers
987
14218588 988fork(), exec(), system(), qx//, and pipe open()s now flush buffers
642f9deb
GS
989of all files opened for output when the operation was attempted. This
990mostly eliminates confusing buffering mishaps suffered by users unaware
991of how Perl internally handles I/O.
45bc9206 992
023ceb80
GS
993This is not supported on some platforms like Solaris where a suitably
994correct implementation of fflush(NULL) isn't available.
995
af8c498a
GS
996=head2 Better diagnostics on meaningless filehandle operations
997
c47ff5f1 998Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
af8c498a
GS
999are compile time errors. Attempting to read from filehandles that
1000were opened only for writing will now produce warnings (just as
1001writing to read-only filehandles does).
1002
a5222a85
GS
1003=head2 Where possible, buffered data discarded from duped input filehandle
1004
c47ff5f1 1005C<< open(NEW, "<&OLD") >> now attempts to discard any data that
a5222a85
GS
1006was previously read and buffered in C<OLD> before duping the handle.
1007On platforms where doing this is allowed, the next read operation
1008on C<NEW> will return the same data as the corresponding operation
1009on C<OLD>. Formerly, it would have returned the data from the start
1010of the following disk block instead.
1011
820475bd
GS
1012=head2 eof() has the same old magic as <>
1013
c47ff5f1 1014C<eof()> would return true if no attempt to read from C<< <> >> had
820475bd 1015yet been made. C<eof()> has been changed to have a little magic of its
c47ff5f1 1016own, it now opens the C<< <> >> files.
820475bd 1017
a5222a85
GS
1018=head2 system(), backticks and pipe open now reflect exec() failure
1019
1020On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1021etc., are implemented via fork() and exec(). When the underlying
1022exec() fails, earlier versions did not report the error properly,
1023since the exec() happened to be in a different process.
1024
1025The child process now communicates with the parent about the
437784d6 1026error in launching the external command, which allows these
a5222a85
GS
1027constructs to return with their usual error value and set $!.
1028
1029=head2 Implicitly closed filehandles are safer
1030
1031Sometimes implicitly closed filehandles (as when they are localized,
1032and Perl automatically closes them on exiting the scope) could
1033inadvertently set $? or $!. This has been corrected.
1034
1035=head2 C<(\$)> prototype and C<$foo{a}>
1036
642f9deb 1037A scalar reference prototype now correctly allows a hash or
a5222a85
GS
1038array element in that slot.
1039
1040=head2 Pseudo-hashes work better
1041
1042Dereferencing some types of reference values in a pseudo-hash,
c47ff5f1 1043such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
a5222a85
GS
1044been corrected.
1045
1046When applied to a pseudo-hash element, exists() now reports whether
1047the specified value exists, not merely if the key is valid.
1048
01020589
GS
1049delete() now works on pseudo-hashes. When given a pseudo-hash element
1050or slice it deletes the values corresponding to the keys (but not the keys
1051themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1052
479ba383
GS
1053Pseudo-hash slices with constant keys are now optimized to array lookups
1054at compile-time.
1055
1056The C<fields> pragma now provides ways to create pseudo-hashes, via
1057fields::new() and fields::phash(). See L<fields>.
1058
a5222a85
GS
1059=head2 C<goto &sub> and AUTOLOAD
1060
08cd8952 1061The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
1062to be autoloaded.
1063
1064=head2 C<-bareword> allowed under C<use integer>
1065
1066The autoquoting of barewords preceded by C<-> did not work
1067in prior versions when the C<integer> pragma was enabled.
1068This has been fixed.
1069
1070=head2 Boolean assignment operators are legal lvalues
1071
1072Constructs such as C<($a ||= 2) += 1> are now allowed.
1073
1074=head2 C<sort $coderef @foo> allowed
1075
1076sort() did not accept a subroutine reference as the comparison
08cd8952 1077function in earlier versions. This is now permitted.
a5222a85
GS
1078
1079=head2 Failures in DESTROY()
1080
1081When code in a destructor threw an exception, it went unnoticed
1082in earlier versions of Perl, unless someone happened to be
1083looking in $@ just after the point the destructor happened to
1084run. Such failures are now visible as warnings when warnings are
1085enabled.
1086
1087=head2 Locale bugs fixed
54195c32 1088
437784d6 1089printf() and sprintf() previously reset the numeric locale
67d3893f
JH
1090back to the default "C" locale. This has been fixed.
1091
1092Numbers formatted according to the local numeric locale
1093(such as using a decimal comma instead of a decimal dot) caused
1094"isn't numeric" warnings, even while the operations accessing
642f9deb
GS
1095those numbers produced correct results. These warnings have been
1096discontinued.
54195c32 1097
a5222a85
GS
1098=head2 Memory leaks
1099
1100The C<eval 'return sub {...}'> construct could sometimes leak
1101memory. This has been fixed.
1102
1103Operations that aren't filehandle constructors used to leak memory
1104when used on invalid filehandles. This has been fixed.
1105
1106Constructs that modified C<@_> could fail to deallocate values
1107in C<@_> and thus leak memory. This has been corrected.
1108
1109=head2 Spurious subroutine stubs after failed subroutine calls
1110
1111Perl could sometimes create empty subroutine stubs when a
1112subroutine was not found in the package. Such cases stopped
1113later method lookups from progressing into base packages.
1114This has been corrected.
1115
a5222a85
GS
1116=head2 Taint failures under C<-U>
1117
1118When running in unsafe mode, taint violations could sometimes
1119cause silent failures. This has been fixed.
1120
1121=head2 END blocks and the C<-c> switch
1122
1123Prior versions used to run BEGIN B<and> END blocks when Perl was
1124run in compile-only mode. Since this is typically not the expected
08cd8952 1125behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
1126is used.
1127
7d30b5c4 1128See L<CHECK blocks> for how to run things when the compile phase ends.
a5222a85
GS
1129
1130=head2 Potential to leak DATA filehandles
1131
1132Using the C<__DATA__> token creates an implicit filehandle to
1133the file that contains the token. It is the program's
1134responsibility to close it when it is done reading from it.
1135
1136This caveat is now better explained in the documentation.
1137See L<perldata>.
1138
1139=head2 Diagnostics follow STDERR
1140
1141Diagnostic output now goes to whichever file the C<STDERR> handle
1142is pointing at, instead of always going to the underlying C runtime
1143library's C<stderr>.
1144
1145=head2 Other fixes for better diagnostics
1146
437784d6 1147Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
1148during the global destruction phase.
1149
1150Diagnostics emitted from code running in threads other than the main
1151thread are now accompanied by the thread ID.
1152
1153Embedded null characters in diagnostics now actually show up. They
1154used to truncate the message in prior versions.
1155
1156$foo::a and $foo::b are now exempt from "possible typo" warnings only
642f9deb 1157if sort() is encountered in package C<foo>.
a5222a85 1158
501fbaef 1159Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
1160constructs now generate a warning, since they may take on new
1161semantics in later versions of Perl.
1162
a398b1cd
GS
1163Many diagnostics now report the internal operation in which the warning
1164was provoked, like so:
1165
1166 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1167 Use of uninitialized value in print at (eval 1) line 1.
1168
1169Diagnostics that occur within eval may also report the file and line
1170number where the eval is located, in addition to the eval sequence
1171number and the line number within the evaluated text itself. For
1172example:
1173
1174 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1175
a5222a85
GS
1176=head1 Performance enhancements
1177
1178=head2 Simple sort() using { $a <=> $b } and the like are optimized
1179
08cd8952 1180Many common sort() operations using a simple inlined block are now
a5222a85
GS
1181optimized for faster performance.
1182
1183=head2 Optimized assignments to lexical variables
1184
1185Certain operations in the RHS of assignment statements have been
1186optimized to directly set the lexical variable on the LHS,
1187eliminating redundant copying overheads.
1188
a5222a85
GS
1189=head2 Faster subroutine calls
1190
1191Minor changes in how subroutine calls are handled internally
1192provide marginal improvements in performance.
1193
1194=head1 Platform specific changes
1195
063663a9 1196=head2 Supported platforms
ba8251e8 1197
5fdc711f
GS
1198=over 4
1199
1200=item *
1201
6c67e1bb
TC
1202VM/ESA is now supported.
1203
5fdc711f
GS
1204=item *
1205
ee3907e2
JH
1206Siemens BS2000 is now supported under the POSIX Shell.
1207
1208=item *
1209
2bb14304
JH
1210The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1211extension.
6c67e1bb 1212
5fdc711f
GS
1213=item *
1214
ee3907e2 1215GNU/Hurd is now supported.
6c67e1bb 1216
00ad96e1
JH
1217=item *
1218
063663a9 1219Rhapsody/Darwin is now supported.
00ad96e1 1220
27806c82
JH
1221=item *
1222
1223EPOC is is now supported (on Psion 5).
1224
5fdc711f
GS
1225=back
1226
a5222a85
GS
1227=head2 DOS
1228
d524f05e
LM
1229=over 4
1230
1231=item *
1232
1233Perl now works with djgpp 2.02 (and 2.03 alpha).
1234
1235=item *
1236
1237Environment variable names are not converted to uppercase any more.
1238
1239=item *
1240
642f9deb 1241Incorrect exit codes from backticks have been fixed.
d524f05e
LM
1242
1243=item *
1244
642f9deb 1245This port continues to use its own builtin globbing (not File::Glob).
d524f05e
LM
1246
1247=back
a5222a85 1248
c6018dae 1249=head2 OS390 (OpenEdition MVS)
063663a9
GS
1250
1251Support for this EBCDIC platform has not been renewed in this release.
1252There are difficulties in reconciling Perl's standardization on UTF-8
1253as its internal representation for characters with the EBCDIC character
1254set, because the two are incompatible.
1255
1256It is unclear whether future versions will renew support for this
1257platform, but the possibility exists.
1258
a5222a85
GS
1259=head2 VMS
1260
c93fa817 1261Numerous revisions and extensions to configuration, build, testing, and
642f9deb 1262installation process to accomodate core changes and VMS-specific options.
c93fa817
GS
1263
1264Expand %ENV-handling code to allow runtime mapping to logical names,
642f9deb 1265CLI symbols, and CRTL environ array.
c93fa817 1266
642f9deb
GS
1267Extension of subprocess invocation code to accept filespecs as command
1268"verbs".
c93fa817
GS
1269
1270Add to Perl command line processing the ability to use default file types and
642f9deb 1271to recognize Unix-style C<2E<gt>&1>.
c93fa817 1272
642f9deb 1273Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
c93fa817 1274
642f9deb 1275Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
c93fa817
GS
1276
1277Barewords at start of Unix-syntax paths may be treated as text rather than
642f9deb 1278only as logical names.
c93fa817 1279
642f9deb 1280Optional secure translation of several logical names used internally by Perl.
c93fa817 1281
642f9deb 1282Miscellaneous bugfixing and porting of new core code to VMS.
c93fa817
GS
1283
1284Thanks are gladly extended to the many people who have contributed VMS
1285patches, testing, and ideas.
a5222a85
GS
1286
1287=head2 Win32
1288
642f9deb
GS
1289Perl can now emulate fork() internally, using multiple interpreters running
1290in different concurrent threads. This support must be enabled at build
1291time. See L<perlfork> for detailed information.
a5222a85 1292
642f9deb
GS
1293When given a pathname that consists only of a drivename, such as C<A:>,
1294opendir() and stat() now use the current working directory for the drive
1295rather than the drive root.
a5222a85 1296
642f9deb
GS
1297The builtin XSUB functions in the Win32:: namespace are documented. See
1298L<Win32>.
a5222a85
GS
1299
1300$^X now contains the full path name of the running executable.
1301
1302A Win32::GetLongPathName() function is provided to complement
1303Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1304
1305POSIX::uname() is supported.
1306
1307system(1,...) now returns true process IDs rather than process
1308handles. kill() accepts any real process id, rather than strictly
1309return values from system(1,...).
1310
42b8b86c
GS
1311For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1312test whether a process exists.
1313
a5222a85
GS
1314The C<Shell> module is supported.
1315
642f9deb 1316Better support for building Perl under command.com in Windows 95
883d36a6
GS
1317has been added.
1318
c39cd008
GS
1319Scripts are read in binary mode by default to allow ByteLoader (and
1320the filter mechanism in general) to work properly. For compatibility,
53129d29
GS
1321the DATA filehandle will be set to text mode if a carriage return is
1322detected at the end of the line containing the __END__ or __DATA__
1323token; if not, the DATA filehandle will be left open in binary mode.
1324Earlier versions always opened the DATA filehandle in text mode.
c39cd008 1325
3a4b19e4 1326The glob() operator is implemented via the C<File::Glob> extension,
8004f2ac 1327which supports glob syntax of the C shell. This increases the flexibility
16070b82
GS
1328of the glob() operator, but there may be compatibility issues for
1329programs that relied on the older globbing syntax. If you want to
642f9deb
GS
1330preserve compatibility with the older syntax, you might want to run
1331perl with C<-MFile::DosGlob>. For details and compatibility information,
1332see L<File::Glob>.
16070b82 1333
6c67e1bb
TC
1334=head1 New tests
1335
1336=over 4
1337
09bef843
SB
1338=item lib/attrs
1339
1340Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1341
2675e62c
GS
1342=item lib/env
1343
1344Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1345
1346=item lib/env-array
1347
1348Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1349
09bef843 1350=item lib/io_const
6c67e1bb
TC
1351
1352IO constants (SEEK_*, _IO*).
14218588 1353
09bef843 1354=item lib/io_dir
6c67e1bb
TC
1355
1356Directory-related IO methods (new, read, close, rewind, tied delete).
1357
09bef843 1358=item lib/io_multihomed
6c67e1bb
TC
1359
1360INET sockets with multi-homed hosts.
1361
09bef843 1362=item lib/io_poll
6c67e1bb
TC
1363
1364IO poll().
1365
09bef843 1366=item lib/io_unix
6c67e1bb
TC
1367
1368UNIX sockets.
1369
09bef843
SB
1370=item op/attrs
1371
1372Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1373
6c67e1bb
TC
1374=item op/filetest
1375
1376File test operators.
1377
1378=item op/lex_assign
1379
5fdc711f 1380Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb 1381
afebc493
GS
1382=item op/exists_sub
1383
1384Verify C<exists &sub> operations.
1385
6c67e1bb 1386=back
e02fdbd2 1387
ba8251e8
GS
1388=head1 Modules and Pragmata
1389
3e8c4fa0
JH
1390=head2 Modules
1391
b7d8191e
JH
1392=over 4
1393
09bef843
SB
1394=item attributes
1395
1396While used internally by Perl as a pragma, this module also
1397provides a way to fetch subroutine and variable attributes.
1398See L<attributes>.
1399
a5222a85
GS
1400=item B
1401
642f9deb
GS
1402 WARNING: The Compiler suite remains highly experimental. The
1403 generated code may not be correct, even it manages to execute
1404 without errors.
501fbaef 1405
c6018dae
GS
1406The Perl Compiler suite has been extensively reworked for this
1407release. More of the standard Perl testsuite passes when run
1408under the Compiler, but there is still a significant way to
1409go to achieve production quality compiled executables.
a5222a85 1410
f29c64d6
GS
1411=item ByteLoader
1412
a5222a85 1413The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1414Perl bytecode. See L<ByteLoader>.
1415
a5222a85
GS
1416=item constant
1417
83763826
GS
1418References can now be used.
1419
1420The new version also allows a leading underscore in constant names, but
1421disallows a double leading underscore (as in "__LINE__"). Some other names
1422are disallowed or warned against, including BEGIN, END, etc. Some names
1423which were forced into main:: used to fail silently in some cases; now they're
1424fatal (outside of main::) and an optional warning (inside of main::).
1425The ability to detect whether a constant had been set with a given name has
1426been added.
1427
1428See L<constant>.
a5222a85
GS
1429
1430=item charnames
1431
21bad921 1432This pragma implements the C<\N> string escape. See L<charnames>.
a5222a85
GS
1433
1434=item Data::Dumper
1435
1436A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1437too deeply into deep data structures. See L<Data::Dumper>.
a5222a85 1438
0f1923bd
GS
1439The XSUB implementation of Dump() is now automatically called if the
1440C<Useqq> setting is not in use.
1441
a5222a85
GS
1442Dumping C<qr//> objects works correctly.
1443
1444=item DB
1445
1446C<DB> is an experimental module that exposes a clean abstraction
1447to Perl's debugging API.
1448
1449=item DB_File
1450
0536e0eb
GS
1451DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1452See C<ext/DB_File/Changes>.
a5222a85 1453
f29c64d6
GS
1454=item Devel::DProf
1455
9e107c59
GS
1456Devel::DProf, a Perl source code profiler has been added. See
1457L<Devel::DProf> and L<dprofpp>.
f29c64d6 1458
b7d8191e
JH
1459=item Dumpvalue
1460
437784d6 1461The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1462
1463=item Benchmark
1464
54e82ce5
GS
1465Overall, Benchmark results exhibit lower average error and better timing
1466accuracy.
1467
868cb350 1468You can now run tests for I<n> seconds instead of guessing the right
642f9deb 1469number of tests to run: e.g., timethese(-5, ...) will run each
14218588 1470code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1471means "for at least 3 CPU seconds". The output format has also
14218588 1472changed. For example:
155776c0 1473
54e82ce5 1474 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1475
1476will now output something like this:
1477
54e82ce5
GS
1478 Benchmark: running a, b, each for at least 5 CPU seconds...
1479 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1480 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1481
1482New features: "each for at least N CPU seconds...", "wallclock secs",
1483and the "@ operations/CPU second (n=operations)".
b7d8191e 1484
54e82ce5
GS
1485timethese() now returns a reference to a hash of Benchmark objects containing
1486the test results, keyed on the names of the tests.
1487
1488timethis() now returns the iterations field in the Benchmark result object
1489instead of 0.
1490
1491timethese(), timethis(), and the new cmpthese() (see below) can also take
1492a format specifier of 'none' to suppress output.
1493
1494A new function countit() is just like timeit() except that it takes a
1495TIME instead of a COUNT.
1496
1497A new function cmpthese() prints a chart comparing the results of each test
1498returned from a timethese() call. For each possible pair of tests, the
1499percentage speed difference (iters/sec or seconds/iter) is shown.
1500
1501For other details, see L<Benchmark>.
a5222a85 1502
f505c983
GS
1503=item Devel::Peek
1504
1505The Devel::Peek module provides access to the internal representation
14218588 1506of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1507
44dcb63b
GS
1508=item English
1509
1510$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1511(a numeric value).
1512
2675e62c
GS
1513=item Env
1514
1515Env now supports accessing environment variables like PATH as array
1516variables.
1517
b7d8191e
JH
1518=item Fcntl
1519
1520More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
55f6b6ec
JH
1521large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1522automatically added to sysopen() flags if large file support has been
1523configured, as is the default), Free/Net/OpenBSD locking behaviour
1524flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1525mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1526constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1527C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1528are available via the C<:mode> tag.
b7d8191e 1529
a5222a85
GS
1530=item File::Compare
1531
1532A compare_text() function has been added, which allows custom
1533comparison functions. See L<File::Compare>.
1534
1535=item File::Find
1536
1537File::Find now works correctly when the wanted() function is either
1538autoloaded or is a symbolic reference.
1539
08cd8952 1540A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1541when pruning top-level directories has been fixed.
1542
81793b90
GS
1543File::Find now also supports several other options to control its
1544behavior. It can follow symbolic links if the C<follow> option is
1545specified. Enabling the C<no_chdir> option will make File::Find skip
1546changing the current directory when walking directories. The C<untaint>
1547flag can be useful when running with taint checks enabled.
1548
1549See L<File::Find>.
1550
becf2bd3
GS
1551=item File::Glob
1552
52bb0670
GS
1553This extension implements BSD-style file globbing. By default,
1554it will also be used for the internal implementation of the glob()
1555operator. See L<File::Glob>.
becf2bd3 1556
f505c983
GS
1557=item File::Spec
1558
1559New methods have been added to the File::Spec module: devnull() returns
19799a22 1560the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1561the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1562to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1563rel2abs(). For compatibility with operating systems that specify volume
1564names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1565have been added.
1566
1567=item File::Spec::Functions
1568
1569The new File::Spec::Functions modules provides a function interface
14218588 1570to the File::Spec module. Allows shorthand
f505c983 1571
14218588 1572 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1573
1574instead of
1575
14218588 1576 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1577
a5222a85
GS
1578=item Getopt::Long
1579
c6edd1b7
GS
1580Getopt::Long licensing has changed to allow the Perl Artistic License
1581as well as the GPL. It used to be GPL only, which got in the way of
1582non-GPL applications that wanted to use Getopt::Long.
1583
1584Getopt::Long encourages the use of Pod::Usage to produce help
1585messages. For example:
1586
1587 use Getopt::Long;
1588 use Pod::Usage;
1589 my $man = 0;
1590 my $help = 0;
1591 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1592 pod2usage(1) if $help;
1593 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1594
1595 __END__
1596
1597 =head1 NAME
1598
1599 sample - Using GetOpt::Long and Pod::Usage
1600
1601 =head1 SYNOPSIS
1602
1603 sample [options] [file ...]
1604
1605 Options:
1606 -help brief help message
1607 -man full documentation
1608
1609 =head1 OPTIONS
1610
1611 =over 8
1612
1613 =item B<-help>
1614
1615 Print a brief help message and exits.
1616
1617 =item B<-man>
1618
1619 Prints the manual page and exits.
1620
1621 =back
1622
1623 =head1 DESCRIPTION
1624
1625 B<This program> will read the given input file(s) and do someting
1626 useful with the contents thereof.
1627
1628 =cut
1629
1630See L<Pod::Usage> for details.
1631
c47ff5f1 1632A bug that prevented the non-option call-back <> from being
c6edd1b7
GS
1633specified as the first argument has been fixed.
1634
c47ff5f1
GS
1635To specify the characters < and > as option starters, use ><. Note,
1636however, that changing option starters is strongly deprecated.
a5222a85
GS
1637
1638=item IO
1639
1640write() and syswrite() will now accept a single-argument
1641form of the call, for consistency with Perl's syswrite().
1642
1643You can now create a TCP-based IO::Socket::INET without forcing
1644a connect attempt. This allows you to configure its options
1645(like making it non-blocking) and then call connect() manually.
1646
1647A bug that prevented the IO::Socket::protocol() accessor
1648from ever returning the correct value has been corrected.
1649
36f31b50
GS
1650IO::Socket::connect now uses non-blocking IO instead of alarm()
1651to do connect timeouts.
1652
1653IO::Socket::accept now uses select() instead of alarm() for doing
1654timeouts.
1655
1656IO::Socket::INET->new now sets $! correctly on failure. $@ is
1657still set for backwards compatability.
1658
a5222a85
GS
1659=item JPL
1660
1661Java Perl Lingo is now distributed with Perl. See jpl/README
1662for more information.
1663
883d36a6
GS
1664=item lib
1665
1666C<use lib> now weeds out any trailing duplicate entries.
1667C<no lib> removes all named entries.
1668
e16b8f49
WM
1669=item Math::BigInt
1670
c47ff5f1 1671The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
e16b8f49
WM
1672and C<~> are now supported on bigints.
1673
b7d8191e 1674=item Math::Complex
7711098a 1675
14218588 1676The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1677act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e 1678
16357284
JH
1679The class method C<display_format> and the corresponding object method
1680C<display_format>, in addition to accepting just one argument, now can
1681also accept a parameter hash. Recognized keys of a parameter hash are
1682C<"style">, which corresponds to the old one parameter case, and two
1683new parameters: C<"format">, which is a printf()-style format string
1684(defaults usually to C<"%.15g">, you can revert to the default by
1685setting the format string to C<undef>) used for both parts of a
1686complex number, and C<"polar_pretty_print"> (defaults to true),
1687which controls whether an attempt is made to try to recognize small
1688multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1689polar complex number.
1690
1691The potentially disruptive change is that in list context both methods
1692now I<return the parameter hash>, instead of only the value of the
1693C<"style"> parameter.
1694
b7d8191e
JH
1695=item Math::Trig
1696
14218588
GS
1697A little bit of radial trigonometry (cylindrical and spherical),
1698radial coordinate conversions, and the great circle distance were added.
b7d8191e 1699
1761cee5 1700=item Pod::Parser, Pod::InputObjects
d4629d6a 1701
1761cee5
JH
1702Pod::Parser is a base class for parsing and selecting sections of
1703pod documentation from an input stream. This module takes care of
1704identifying pod paragraphs and commands in the input and hands off the
1705parsed paragraphs and commands to user-defined methods which are free
1706to interpret or translate them as they see fit.
d4629d6a
GS
1707
1708Pod::InputObjects defines some input objects needed by Pod::Parser, and
1709for advanced users of Pod::Parser that need more about a command besides
1761cee5 1710its name and text.
d4629d6a 1711
21bad921 1712As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
d4629d6a
GS
1713"base parser code" recommended for use by all pod2xxx translators.
1714Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1761cee5
JH
1715to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1716underway. For any questions or comments about pod parsing and translating
1717issues and utilities, please use the pod-people@perl.org mailing list.
d4629d6a 1718
1761cee5 1719For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
d4629d6a 1720
1761cee5 1721=item Pod::Checker, podchecker
d4629d6a 1722
1761cee5
JH
1723This utility checks pod files for correct syntax, according to
1724L<perlpod>. Obvious errors are flagged as such, while warnings are
1725printed for mistakes that can be handled gracefully. The checklist is
1726not complete yet. See L<Pod::Checker>.
d4629d6a 1727
1761cee5 1728=item Pod::ParseUtils, Pod::Find
d4629d6a 1729
1761cee5
JH
1730These modules provide a set of gizmos that are useful mainly for pod
1731translators. L<Pod::Find|Pod::Find> traverses directory structures and
1732returns found pod files, along with their canonical names (like
1733C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1734B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
c47ff5f1 1735(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
642f9deb 1736(for caching information about pod files, e.g., link nodes).
d4629d6a 1737
1761cee5 1738=item Pod::Select, podselect
d4629d6a 1739
1761cee5
JH
1740Pod::Select is a subclass of Pod::Parser which provides a function
1741named "podselect()" to filter out user-specified sections of raw pod
1742documentation from an input stream. podselect is a script that provides
1743access to Pod::Select from other scripts to be used as a filter.
1744See L<Pod::Select>.
d4629d6a 1745
1761cee5 1746=item Pod::Usage, pod2usage
d4629d6a 1747
1761cee5
JH
1748Pod::Usage provides the function "pod2usage()" to print usage messages for
1749a Perl script based on its embedded pod documentation. The pod2usage()
1750function is generally useful to all script authors since it lets them
1751write and maintain a single source (the pods) for documentation, thus
1752removing the need to create and maintain redundant usage message text
1753consisting of information already in the pods.
d4629d6a 1754
1761cee5
JH
1755There is also a pod2usage script which can be used from other kinds of
1756scripts to print usage messages from pods (even for non-Perl scripts
1757with pods embedded in comments).
a5222a85 1758
1761cee5 1759For details and examples, please see L<Pod::Usage>.
a5222a85
GS
1760
1761=item Pod::Text and Pod::Man
1762
e3e5e1ea
GS
1763Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1764still available for backwards compatibility, the module now has a new
1765preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1766module is easily subclassed for tweaks to the output, and two such
1767subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1768using termcap information, and Pod::Text::Color for markup with ANSI color
1769sequences) are now standard.
1770
1771pod2man has been turned into a module, Pod::Man, which also uses
1772Pod::Parser. In the process, several outstanding bugs related to quotes
1773in section headers, quoting of code escapes, and nested lists have been
1774fixed. pod2man is now a wrapper script around this module.
a5222a85 1775
f4b9d880
RA
1776=item SDBM_File
1777
1778An EXISTS method has been added to this module (and sdbm_exists() has
1779been added to the underlying sdbm library), so one can now call exists
14218588 1780on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1781runtime error.
1782
a5222a85
GS
1783A bug that may have caused data loss when more than one disk block
1784happens to be read from the database in a single FETCH() has been
1785fixed.
1786
8ce86de8
GS
1787=item Sys::Syslog
1788
1789Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1790no longer requires syslog.ph to exist.
1791
f91101c9
GS
1792=item Sys::Hostname
1793
1794Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1795uname() if they exist.
1796
e3e5e1ea
GS
1797=item Term::ANSIColor
1798
1799Term::ANSIColor is a very simple module to provide easy and readable
1800access to the ANSI color and highlighting escape sequences, supported by
1801most ANSI terminal emulators. It is now included standard.
1802
06ef4121
PC
1803=item Time::Local
1804
1805The timelocal() and timegm() functions used to silently return bogus
437784d6 1806results when the date fell outside the machine's integer range. They
a5222a85 1807now consistently croak() if the date falls in an unsupported range.
06ef4121 1808
8fe0a5c4
JD
1809=item Win32
1810
1811The error return value in list context has been changed for all functions
14218588
GS
1812that return a list of values. Previously these functions returned a list
1813with a single element C<undef> if an error occurred. Now these functions
1814return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1815functions:
1816
14218588
GS
1817 Win32::FsType
1818 Win32::GetOSVersion
8fe0a5c4
JD
1819
1820The remaining functions are unchanged and continue to return C<undef> on
1821error even in list context.
1822
1823The Win32::SetLastError(ERROR) function has been added as a complement
1824to the Win32::GetLastError() function.
1825
1826The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1827pathname for FILENAME in scalar context. In list context it returns
1828a two-element list containing the fully qualified directory name and
501fbaef 1829the filename. See L<Win32>.
8fe0a5c4 1830
9fe6733a
PM
1831=item DBM Filters
1832
1833A new feature called "DBM Filters" has been added to all the
14218588
GS
1834DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1835DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1836
1837 filter_store_key
1838 filter_store_value
1839 filter_fetch_key
1840 filter_fetch_value
1841
14218588 1842These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1843written to the database or just after they are read from the database.
1844See L<perldbmfilter> for further information.
1845
b7d8191e 1846=back
3e8c4fa0
JH
1847
1848=head2 Pragmata
1849
437784d6 1850C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1851backward-compatibility. It's been replaced by the C<sub : attributes>
1852syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1853
4438c4b7 1854Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1855See L<perllexwarn>.
6c67e1bb 1856
67d3893f
JH
1857C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1858...). Currently only one subpragma implemented, "use filetest
1859'access';", that uses access(2) or equivalent to check permissions
1860instead of using stat(2) as usual. This matters in filesystems
1861where there are ACLs (access control lists): the stat(2) might lie,
1862but access(2) knows better.
6c67e1bb 1863
ba8251e8
GS
1864=head1 Utility Changes
1865
a5222a85
GS
1866=head2 perlcc
1867
1868C<perlcc> now supports the C and Bytecode backends. By default,
1869it generates output from the simple C backend rather than the
1870optimized C backend.
1871
1872Support for non-Unix platforms has been improved.
1873
055fd3a9
GS
1874=head2 perldoc
1875
1876C<perldoc> has been reworked to avoid possible security holes.
1877It will not by default let itself be run as the superuser, but you
1878may still use the B<-U> switch to try to make it drop privileges
1879first.
1880
1881=head2 The Perl Debugger
1882
1883Many bug fixes and enhancements were added to F<perl5db.pl>, the
1884Perl debugger. The help documentation was rearranged. New commands
1885include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1886actions, C<man I<docpage>> to run your doc viewer on some perl
1887docset, and support for quoted options. The help information was
1888rearranged, and should be viewable once again if you're using B<less>
1889as your pager. A serious security hole was plugged--you should
1890immediately remove all older versions of the Perl debugger as
1891installed in previous releases, all the way back to perl3, from
1892your system to avoid being bitten by this.
1893
ba8251e8
GS
1894=head1 Documentation Changes
1895
5fdc711f
GS
1896=over 4
1897
954c1994
GS
1898=item perlapi.pod
1899
1900The official list of public Perl API functions.
1901
883d36a6
GS
1902=item perlcompile.pod
1903
1904An introduction to using the Perl Compiler suite.
1905
055fd3a9
GS
1906=item perldebug.pod
1907
1908All material unrelated to running the Perl debugger, plus all
1909low-level guts-like details that risked crushing the casual user
1910of the debugger, have been relocated from the old manpage to the
1911next entry below.
1912
1913=item perldebguts.pod
1914
1915This new manpage contains excessively low-level material not related
1916to the Perl debugger, but slightly related to debugging Perl itself.
1917It also contains some arcane internal details of how the debugging
1918process works that may only be of interest to developers of Perl
1919debuggers.
1920
c7c04614
GS
1921=item perlfilter.pod
1922
1923An introduction to writing Perl source filters.
1924
883d36a6
GS
1925=item perlhack.pod
1926
1927Some guidelines for hacking the Perl source code.
1928
954c1994
GS
1929=item perlintern.pod
1930
1931A list of internal functions in the Perl source code.
1932(List is currently empty.)
1933
5fdc711f 1934=item perlopentut.pod
f8284313 1935
5fdc711f
GS
1936A tutorial on using open() effectively.
1937
1938=item perlreftut.pod
1939
1940A tutorial that introduces the essentials of references.
1941
694468e3
GS
1942=item perlboot.pod
1943
1944A tutorial for beginners on object-oriented Perl.
1945
14218588
GS
1946=item perltootc.pod
1947
1948A tutorial on managing class data for object modules.
1949
393fec97
GS
1950=item perlunicode.pod
1951
1952An introduction to Unicode support features in Perl.
1953
5fdc711f 1954=back
e02fdbd2 1955
73b437c8 1956=head1 New or Changed Diagnostics
ba8251e8 1957
a99ba403
GS
1958=over 4
1959
56e90b21
GS
1960=item "%s" variable %s masks earlier declaration in same %s
1961
ddda08b7 1962(W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
56e90b21
GS
1963effectively eliminating all access to the previous instance. This is almost
1964always a typographical error. Note that the earlier variable will still exist
1965until the end of the scope or until all closure referents to it are
1966destroyed.
1967
33633739
GS
1968=item "my sub" not yet implemented
1969
1970(F) Lexically scoped subroutines are not yet implemented. Don't try that
1971yet.
1972
1973=item "our" variable %s redeclared
1974
ddda08b7 1975(W misc) You seem to have already declared the same global once before in the
33633739
GS
1976current lexical scope.
1977
a99ba403
GS
1978=item '!' allowed only after types %s
1979
1980(F) The '!' is allowed in pack() and unpack() only after certain types.
1981See L<perlfunc/pack>.
1982
1983=item / cannot take a count
1984
1985(F) You had an unpack template indicating a counted-length string,
1986but you have also specified an explicit size for the string.
1987See L<perlfunc/pack>.
1988
1989=item / must be followed by a, A or Z
1990
1991(F) You had an unpack template indicating a counted-length string,
1992which must be followed by one of the letters a, A or Z
1993to indicate what sort of string is to be unpacked.
1994See L<perlfunc/pack>.
1995
1996=item / must be followed by a*, A* or Z*
1997
437784d6 1998(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1999Currently the only things that can have their length counted are a*, A* or Z*.
2000See L<perlfunc/pack>.
2001
2002=item / must follow a numeric type
2003
2004(F) You had an unpack template that contained a '#',
2005but this did not follow some numeric unpack specification.
2006See L<perlfunc/pack>.
2007
a99ba403
GS
2008=item /%s/: Unrecognized escape \\%c passed through
2009
ddda08b7 2010(W regexp) You used a backslash-character combination which is not recognized
a99ba403 2011by Perl. This combination appears in an interpolated variable or a
1028017a
JH
2012C<'>-delimited regular expression. The character was understood literally.
2013
2014=item /%s/: Unrecognized escape \\%c in character class passed through
2015
ddda08b7 2016(W regexp) You used a backslash-character combination which is not recognized
1028017a 2017by Perl inside character classes. The character was understood literally.
a99ba403
GS
2018
2019=item /%s/ should probably be written as "%s"
2020
ddda08b7 2021(W syntax) You have used a pattern where Perl expected to find a string,
437784d6 2022as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
2023or false result of matching the pattern against $_ as the string,
2024which is probably not what you had in mind.
2025
2026=item %s() called too early to check prototype
2027
ddda08b7 2028(W prototype) You've called a function that has a prototype before the parser saw a
a99ba403
GS
2029definition or declaration for it, and Perl could not check that the call
2030conforms to the prototype. You need to either add an early prototype
2031declaration for the subroutine in question, or move the subroutine
2032definition ahead of the call to get proper prototype checking. Alternatively,
2033if you are certain that you're calling the function correctly, you may put
2034an ampersand before the name to avoid the warning. See L<perlsub>.
2035
56e90b21
GS
2036=item %s argument is not a HASH or ARRAY element
2037
2038(F) The argument to exists() must be a hash or array element, such as:
2039
2040 $foo{$bar}
2041 $ref->[12]->["susie"]
2042
2043=item %s argument is not a HASH or ARRAY element or slice
2044
2045(F) The argument to delete() must be either a hash or array element, such as:
2046
2047 $foo{$bar}
2048 $ref->[12]->["susie"]
2049
2050or a hash or array slice, such as:
2051
2052 @foo[$bar, $baz, $xyzzy]
2053 @{$ref->[12]}{"susie", "queue"}
2054
afebc493
GS
2055=item %s argument is not a subroutine name
2056
2057(F) The argument to exists() for C<exists &sub> must be a subroutine
2058name, and not a subroutine call. C<exists &sub()> will generate this error.
2059
09bef843
SB
2060=item %s package attribute may clash with future reserved word: %s
2061
ddda08b7 2062(W reserved) A lowercase attribute name was used that had a package-specific handler.
09bef843
SB
2063That name might have a meaning to Perl itself some day, even though it
2064doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2065See L<attributes>.
2066
a99ba403 2067=item (in cleanup) %s
6b121555 2068
ddda08b7 2069(W misc) This prefix usually indicates that a DESTROY() method raised
a99ba403
GS
2070the indicated exception. Since destructors are usually called by
2071the system at arbitrary points during execution, and often a vast
2072number of times, the warning is issued only once for any number
2073of failures that would otherwise result in the same message being
2074repeated.
2075
2076Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2077could also result in this warning. See L<perlcall/G_KEEPERR>.
2078
2079=item <> should be quotes
2080
c47ff5f1 2081(F) You wrote C<< require <file> >> when you should have written
a99ba403
GS
2082C<require 'file'>.
2083
2084=item Attempt to join self
2085
2086(F) You tried to join a thread from within itself, which is an
2087impossible task. You may be joining the wrong thread, or you may
2088need to move the join() to some other thread.
2089
2090=item Bad evalled substitution pattern
2091
2092(F) You've used the /e switch to evaluate the replacement for a
2093substitution, but perl found a syntax error in the code to evaluate,
2094most likely an unexpected right brace '}'.
2095
2096=item Bad realloc() ignored
2097
2098(S) An internal routine called realloc() on something that had never been
2099malloc()ed in the first place. Mandatory, but can be disabled by
2100setting environment variable C<PERL_BADFREE> to 1.
2101
34d09196
GS
2102=item Bareword found in conditional
2103
ddda08b7 2104(W bareword) The compiler found a bareword where it expected a conditional,
34d09196
GS
2105which often indicates that an || or && was parsed as part of the
2106last argument of the previous construct, for example:
2107
2108 open FOO || die;
2109
2110It may also indicate a misspelled constant that has been interpreted
2111as a bareword:
2112
2113 use constant TYPO => 1;
2114 if (TYOP) { print "foo" }
2115
2116The C<strict> pragma is useful in avoiding such errors.
2117
a99ba403
GS
2118=item Binary number > 0b11111111111111111111111111111111 non-portable
2119
ddda08b7 2120(W portable) The binary number you specified is larger than 2**32-1
a99ba403
GS
2121(4294967295) and therefore non-portable between systems. See
2122L<perlport> for more on portability concerns.
2123
2124=item Bit vector size > 32 non-portable
2125
ddda08b7 2126(W portable) Using bit vector sizes larger than 32 is non-portable.
a99ba403
GS
2127
2128=item Buffer overflow in prime_env_iter: %s
2129
ddda08b7 2130(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
a99ba403
GS
2131%ENV, it encountered a logical name or symbol definition which was too long,
2132so it was truncated to the string shown.
2133
2134=item Can't check filesystem of script "%s"
2135
2136(P) For some reason you can't check the filesystem of the script for nosuid.
2137
56e90b21
GS
2138=item Can't declare class for non-scalar %s in "%s"
2139
2140(S) Currently, only scalar variables can declared with a specific class
2141qualifier in a "my" or "our" declaration. The semantics may be extended
2142for other types of variables in future.
2143
2144=item Can't declare %s in "%s"
2145
2146(F) Only scalar, array, and hash variables may be declared as "my" or
2147"our" variables. They must have ordinary identifiers as names.
2148
0b5b802d
GS
2149=item Can't ignore signal CHLD, forcing to default
2150
ddda08b7 2151(W signal) Perl has detected that it is being run with the SIGCHLD signal
0b5b802d
GS
2152(sometimes known as SIGCLD) disabled. Since disabling this signal
2153will interfere with proper determination of exit status of child
2154processes, Perl has reset the signal to its default value.
2155This situation typically indicates that the parent program under
642f9deb 2156which Perl may be running (e.g., cron) is being very careless.
0b5b802d 2157
a99ba403
GS
2158=item Can't modify non-lvalue subroutine call
2159
437784d6
GS
2160(F) Subroutines meant to be used in lvalue context should be declared as
2161such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
2162
2163=item Can't read CRTL environ
2164
2165(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2166from the CRTL's internal environment array and discovered the array was
2167missing. You need to figure out where your CRTL misplaced its environ
2168or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2169
2170=item Can't remove %s: %s, skipping file
2171
2172(S) You requested an inplace edit without creating a backup file. Perl
2173was unable to remove the original file to replace it with the modified
2174file. The file was left unmodified.
2175
2176=item Can't return %s from lvalue subroutine
2177
2178(F) Perl detected an attempt to return illegal lvalues (such
2179as temporary or readonly values) from a subroutine used as an lvalue.
2180This is not allowed.
2181
2182=item Can't weaken a nonreference
2183
2184(F) You attempted to weaken something that was not a reference. Only
2185references can be weakened.
2186
2187=item Character class [:%s:] unknown
2188
2189(F) The class in the character class [: :] syntax is unknown.
437784d6 2190See L<perlre>.
a99ba403
GS
2191
2192=item Character class syntax [%s] belongs inside character classes
2193
ddda08b7 2194(W unsafe) The character class constructs [: :], [= =], and [. .] go
a99ba403 2195I<inside> character classes, the [] are part of the construct,
437784d6
GS
2196for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2197are not currently implemented; they are simply placeholders for
2198future extensions.
a99ba403
GS
2199
2200=item Constant is not %s reference
2201
2202(F) A constant value (perhaps declared using the C<use constant> pragma)
2203is being dereferenced, but it amounts to the wrong type of reference. The
2204message indicates the type of reference that was expected. This usually
2205indicates a syntax error in dereferencing the constant value.
2206See L<perlsub/"Constant Functions"> and L<constant>.
2207
a99ba403
GS
2208=item constant(%s): %s
2209
f0af216f
GS
2210(F) The parser found inconsistencies either while attempting to define an
2211overloaded constant, or when trying to find the character name specified
2212in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
2213C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
a99ba403 2214
6798c92b
GS
2215=item CORE::%s is not a keyword
2216
2217(F) The CORE:: namespace is reserved for Perl keywords.
2218
a99ba403
GS
2219=item defined(@array) is deprecated
2220
2221(D) defined() is not usually useful on arrays because it checks for an
2222undefined I<scalar> value. If you want to see if the array is empty,
2223just use C<if (@array) { # not empty }> for example.
2224
2225=item defined(%hash) is deprecated
2226
2227(D) defined() is not usually useful on hashes because it checks for an
2228undefined I<scalar> value. If you want to see if the hash is empty,
2229just use C<if (%hash) { # not empty }> for example.
2230
2231=item Did not produce a valid header
2232
2233See Server error.
2234
33633739
GS
2235=item Did you mean "local" instead of "our"?
2236
ddda08b7 2237(W misc) Remember that "our" does not localize the declared global variable.
33633739
GS
2238You have declared it again in the same lexical scope, which seems superfluous.
2239
a99ba403
GS
2240=item Document contains no data
2241
2242See Server error.
2243
2244=item entering effective %s failed
2245
2246(F) While under the C<use filetest> pragma, switching the real and
2247effective uids or gids failed.
6b121555 2248
73b437c8
JH
2249=item false [] range "%s" in regexp
2250
ddda08b7 2251(W regexp) A character class range must start and end at a literal character, not
73b437c8
JH
2252another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2253range is interpreted as a literal "-". Consider quoting the "-", "\-".
2254See L<perlre>.
2255
af8c498a 2256=item Filehandle %s opened only for output
6b121555 2257
ddda08b7 2258(W io) You tried to read from a filehandle opened only for writing. If you
437784d6 2259intended it to be a read/write filehandle, you needed to open it with
c47ff5f1
GS
2260"+<" or "+>" or "+>>" instead of with "<" or nothing. If
2261you intended only to read from the file, use "<". See
af8c498a 2262L<perlfunc/open>.
e02fdbd2 2263
56e90b21
GS
2264=item flock() on closed filehandle %s
2265
ddda08b7 2266(W closed) The filehandle you're attempting to flock() got itself closed some
56e90b21
GS
2267time before now. Check your logic flow. flock() operates on filehandles.
2268Are you attempting to call flock() on a dirhandle by the same name?
2269
2270=item Global symbol "%s" requires explicit package name
2271
2272(F) You've said "use strict vars", which indicates that all variables
2273must either be lexically scoped (using "my"), declared beforehand using
2274"our", or explicitly qualified to say which package the global variable
2275is in (using "::").
2276
a99ba403
GS
2277=item Hexadecimal number > 0xffffffff non-portable
2278
ddda08b7 2279(W portable) The hexadecimal number you specified is larger than 2**32-1
a99ba403
GS
2280(4294967295) and therefore non-portable between systems. See
2281L<perlport> for more on portability concerns.
2282
2283=item Ill-formed CRTL environ value "%s"
2284
ddda08b7 2285(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
a99ba403
GS
2286environ array, and encountered an element without the C<=> delimiter
2287used to spearate keys from values. The element is ignored.
2288
2289=item Ill-formed message in prime_env_iter: |%s|
2290
ddda08b7 2291(W internal) A warning peculiar to VMS. Perl tried to read a logical name
a99ba403
GS
2292or CLI symbol definition when preparing to iterate over %ENV, and
2293didn't see the expected delimiter between key and value, so the
2294line was ignored.
2295
2296=item Illegal binary digit %s
2297
437784d6 2298(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
2299
2300=item Illegal binary digit %s ignored
2301
ddda08b7 2302(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
a99ba403
GS
2303Interpretation of the binary number stopped before the offending digit.
2304
2305=item Illegal number of bits in vec
2306
2307(F) The number of bits in vec() (the third argument) must be a power of
2308two from 1 to 32 (or 64, if your platform supports that).
2309
2310=item Integer overflow in %s number
2311
ddda08b7 2312(W overflow) The hexadecimal, octal or binary number you have specified either
c6edd1b7 2313as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
2314architecture, and has been converted to a floating point number. On a
231532-bit architecture the largest hexadecimal, octal or binary number
2316representable without overflow is 0xFFFFFFFF, 037777777777, or
23170b11111111111111111111111111111111 respectively. Note that Perl
2318transparently promotes all numbers to a floating point representation
2319internally--subject to loss of precision errors in subsequent
2320operations.
2321
09bef843
SB
2322=item Invalid %s attribute: %s
2323
2324The indicated attribute for a subroutine or variable was not recognized
2325by Perl or by a user-supplied handler. See L<attributes>.
2326
2327=item Invalid %s attributes: %s
2328
2329The indicated attributes for a subroutine or variable were not recognized
2330by Perl or by a user-supplied handler. See L<attributes>.
2331
73b437c8
JH
2332=item invalid [] range "%s" in regexp
2333
2334The offending range is now explicitly displayed.
2335
09bef843
SB
2336=item Invalid separator character %s in attribute list
2337
0120eecf 2338(F) Something other than a colon or whitespace was seen between the
09bef843
SB
2339elements of an attribute list. If the previous attribute
2340had a parenthesised parameter list, perhaps that list was terminated
2341too soon. See L<attributes>.
2342
a99ba403
GS
2343=item Invalid separator character %s in subroutine attribute list
2344
0120eecf 2345(F) Something other than a colon or whitespace was seen between the
a99ba403
GS
2346elements of a subroutine attribute list. If the previous attribute
2347had a parenthesised parameter list, perhaps that list was terminated
2348too soon.
2349
2350=item leaving effective %s failed
2351
2352(F) While under the C<use filetest> pragma, switching the real and
2353effective uids or gids failed.
2354
2355=item Lvalue subs returning %s not implemented yet
2356
2357(F) Due to limitations in the current implementation, array and hash
2358values cannot be returned in subroutines used in lvalue context.
2359See L<perlsub/"Lvalue subroutines">.
2360
2361=item Method %s not permitted
2362
2363See Server error.
2364
2365=item Missing %sbrace%s on \N{}
2366
2367(F) Wrong syntax of character name literal C<\N{charname}> within
2368double-quotish context.
2369
06eaf0bc
GS
2370=item Missing command in piped open
2371
ddda08b7 2372(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
06eaf0bc
GS
2373construction, but the command was missing or blank.
2374
09bef843
SB
2375=item Missing name in "my sub"
2376
2377(F) The reserved syntax for lexically scoped subroutines requires that they
2378have a name with which they can be found.
2379
56e90b21
GS
2380=item No %s specified for -%c
2381
2382(F) The indicated command line switch needs a mandatory argument, but
2383you haven't specified one.
2384
2385=item No package name allowed for variable %s in "our"
2386
2387(F) Fully qualified variable names are not allowed in "our" declarations,
2388because that doesn't make much sense under existing semantics. Such
2389syntax is reserved for future extensions.
2390
2391=item No space allowed after -%c
2392
2393(F) The argument to the indicated command line switch must follow immediately
2394after the switch, without intervening spaces.
2395
a99ba403
GS
2396=item no UTC offset information; assuming local time is UTC
2397
2398(S) A warning peculiar to VMS. Perl was unable to find the local
2399timezone offset, so it's assuming that local system time is equivalent
2400to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2401to translate to the number of seconds which need to be added to UTC to
2402get local time.
2403
2404=item Octal number > 037777777777 non-portable
2405
ddda08b7 2406(W portable) The octal number you specified is larger than 2**32-1 (4294967295)
a99ba403
GS
2407and therefore non-portable between systems. See L<perlport> for more
2408on portability concerns.
2409
2410See also L<perlport> for writing portable code.
2411
2412=item panic: del_backref
2413
2414(P) Failed an internal consistency check while trying to reset a weak
2415reference.
2416
2417=item panic: kid popen errno read
2418
2419(F) forked child returned an incomprehensible message about its errno.
2420
2421=item panic: magic_killbackrefs
2422
2423(P) Failed an internal consistency check while trying to reset all weak
2424references to an object.
2425
56e90b21
GS
2426=item Parentheses missing around "%s" list
2427
ddda08b7 2428(W parenthesis) You said something like
56e90b21
GS
2429
2430 my $foo, $bar = @_;
2431
2432when you meant
2433
2434 my ($foo, $bar) = @_;
2435
54884818 2436Remember that "my", "our", and "local" bind tighter than comma.
56e90b21 2437
a99ba403
GS
2438=item Possible Y2K bug: %s
2439
ddda08b7 2440(W y2k) You are concatenating the number 19 with another number, which
a99ba403
GS
2441could be a potential Year 2000 problem.
2442
8cd79558
GS
2443=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2444
ddda08b7 2445(W deprecated) You have written somehing like this:
8cd79558
GS
2446
2447 sub doit
2448 {
2449 use attrs qw(locked);
2450 }
2451
2452You should use the new declaration syntax instead.
2453
2454 sub doit : locked
2455 {
2456 ...
2457
2458The C<use attrs> pragma is now obsolete, and is only provided for
2459backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2460
2461
a99ba403
GS
2462=item Premature end of script headers
2463
2464See Server error.
2465
0b5b802d
GS
2466=item Repeat count in pack overflows
2467
2468(F) You can't specify a repeat count so large that it overflows
2469your signed integers. See L<perlfunc/pack>.
2470
2471=item Repeat count in unpack overflows
2472
2473(F) You can't specify a repeat count so large that it overflows
2474your signed integers. See L<perlfunc/unpack>.
2475
a99ba403
GS
2476=item realloc() of freed memory ignored
2477
2478(S) An internal routine called realloc() on something that had already
2479been freed.
2480
2481=item Reference is already weak
2482
ddda08b7 2483(W misc) You have attempted to weaken a reference that is already weak.
a99ba403
GS
2484Doing so has no effect.
2485
2486=item setpgrp can't take arguments
2487
2488(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2489unlike POSIX setpgid(), which takes a process ID and process group ID.
2490
2491=item Strange *+?{} on zero-length expression
2492
ddda08b7 2493(W regexp) You applied a regular expression quantifier in a place where it
a99ba403
GS
2494makes no sense, such as on a zero-width assertion.
2495Try putting the quantifier inside the assertion instead. For example,
2496the way to match "abc" provided that it is followed by three
2497repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2498
2499=item switching effective %s is not implemented
2500
2501(F) While under the C<use filetest> pragma, we cannot switch the
2502real and effective uids or gids.
2503
437784d6 2504=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
2505
2506=item This Perl can't set CRTL environ elements (%s=%s)
2507
ddda08b7 2508(W internal) Warnings peculiar to VMS. You tried to change or delete an element
a99ba403
GS
2509of the CRTL's internal environ array, but your copy of Perl wasn't
2510built with a CRTL that contained the setenv() function. You'll need to
2511rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2512L<perlvms>) so that the environ array isn't the target of the change to
2513%ENV which produced the warning.
2514
ddda08b7
GS
2515=item Too late to run %s block
2516
2517(W void) A CHECK or INIT block is being defined during run time proper,
2518when the opportunity to run them has already passed. Perhaps you are
2519loading a file with C<require> or C<do> when you should be using
2520C<use> instead. Or perhaps you should put the C<require> or C<do>
2521inside a BEGIN block.
2522
a99ba403
GS
2523=item Unknown open() mode '%s'
2524
437784d6 2525(F) The second argument of 3-argument open() is not among the list
c47ff5f1
GS
2526of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2527C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
a99ba403
GS
2528
2529=item Unknown process %x sent message to prime_env_iter: %s
2530
2531(P) An error peculiar to VMS. Perl was reading values for %ENV before
2532iterating over it, and someone else stuck a message in the stream of
2533data Perl expected. Someone's very confused, or perhaps trying to
2534subvert Perl's population of %ENV for nefarious purposes.
2535
af8c498a
GS
2536=item Unrecognized escape \\%c passed through
2537
ddda08b7 2538(W misc) You used a backslash-character combination which is not recognized
1028017a 2539by Perl. The character was understood literally.
af8c498a 2540
09bef843
SB
2541=item Unterminated attribute parameter in attribute list
2542
2543(F) The lexer saw an opening (left) parenthesis character while parsing an
2544attribute list, but the matching closing (right) parenthesis
2545character was not found. You may need to add (or remove) a backslash
2546character to get your parentheses to balance. See L<attributes>.
2547
2548=item Unterminated attribute list
2549
2550(F) The lexer found something other than a simple identifier at the start
2551of an attribute, and it wasn't a semicolon or the start of a
2552block. Perhaps you terminated the parameter list of the previous attribute
2553too soon. See L<attributes>.
2554
09bef843
SB
2555=item Unterminated attribute parameter in subroutine attribute list
2556
2557(F) The lexer saw an opening (left) parenthesis character while parsing a
2558subroutine attribute list, but the matching closing (right) parenthesis
2559character was not found. You may need to add (or remove) a backslash
2560character to get your parentheses to balance.
2561
2562=item Unterminated subroutine attribute list
2563
2564(F) The lexer found something other than a simple identifier at the start
2565of a subroutine attribute, and it wasn't a semicolon or the start of a
2566block. Perhaps you terminated the parameter list of the previous attribute
2567too soon.
2568
a99ba403 2569=item Value of CLI symbol "%s" too long
eb6e2d6f 2570
ddda08b7 2571(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
a99ba403
GS
2572element from a CLI symbol table, and found a resultant string longer
2573than 1024 characters. The return value has been truncated to 1024
2574characters.
eb6e2d6f 2575
a99ba403 2576=item Version number must be a constant number
ba8251e8 2577
a99ba403
GS
2578(P) The attempt to translate a C<use Module n.n LIST> statement into
2579its equivalent C<BEGIN> block found an internal inconsistency with
2580the version number.
2581
2582=back
27806c82 2583
a5222a85 2584=head1 Obsolete Diagnostics
3175b8cd 2585
a99ba403
GS
2586=over 4
2587
2588=item Character class syntax [: :] is reserved for future extensions
2589
2590(W) Within regular expression character classes ([]) the syntax beginning
2591with "[:" and ending with ":]" is reserved for future extensions.
2592If you need to represent those character sequences inside a regular
2593expression character class, just quote the square brackets with the
2594backslash: "\[:" and ":\]".
2595
2596=item Ill-formed logical name |%s| in prime_env_iter
2597
2598(W) A warning peculiar to VMS. A logical name was encountered when preparing
2599to iterate over %ENV which violates the syntactic rules governing logical
2600names. Because it cannot be translated normally, it is skipped, and will not
2601appear in %ENV. This may be a benign occurrence, as some software packages
2602might directly modify logical name tables and introduce nonstandard names,
2603or it may indicate that a logical name table has been corrupted.
2604
34d09196
GS
2605=item Probable precedence problem on %s
2606
2607(W) The compiler found a bareword where it expected a conditional,
2608which often indicates that an || or && was parsed as part of the
2609last argument of the previous construct, for example:
2610
2611 open FOO || die;
2612
a99ba403
GS
2613=item regexp too big
2614
2615(F) The current implementation of regular expressions uses shorts as
2616address offsets within a string. Unfortunately this means that if
2617the regular expression compiles to longer than 32767, it'll blow up.
2618Usually when you want a regular expression this big, there is a better
2619way to do it with multiple statements. See L<perlre>.
2620
2621=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2622
2623(D) Perl versions before 5.004 misinterpreted any type marker followed
2624by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2625"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2626
2627However, the developers of Perl 5.004 could not fix this bug completely,
2628because at least two widely-used modules depend on the old meaning of
2629"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2630old (broken) way inside strings; but it generates this message as a
2631warning. And in Perl 5.005, this special treatment will cease.
2632
2633=back
3175b8cd 2634
ba8251e8
GS
2635=head1 BUGS
2636
437784d6 2637If you find what you think is a bug, you might check the
14218588 2638articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
GS
2639There may also be information at http://www.perl.com/perl/, the Perl
2640Home Page.
2641
2642If you believe you have an unreported bug, please run the B<perlbug>
642f9deb 2643program included with your release. Be sure to trim your bug down
ba8251e8 2644to a tiny but sufficient test case. Your bug report, along with the
14218588 2645output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
GS
2646analysed by the Perl porting team.
2647
2648=head1 SEE ALSO
2649
2650The F<Changes> file for exhaustive details on what changed.
2651
2652The F<INSTALL> file for how to build Perl.
2653
2654The F<README> file for general stuff.
2655
2656The F<Artistic> and F<Copying> files for copyright information.
2657
2658=head1 HISTORY
2659
a5222a85
GS
2660Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2661contributions from The Perl Porters.
ba8251e8
GS
2662
2663Send omissions or corrections to <F<perlbug@perl.com>>.
2664
2665=cut