3 perldelta - what's new for perl v5.6 (as of v5.005_64)
7 This is an unsupported alpha release, meant for intrepid Perl
8 developers only. The included sources may not even build correctly on
9 some platforms. Subscribing to perl5-porters is the best way to
10 monitor and contribute to the progress of development releases (see
11 http://www.hut.fi/~jhi/perl5-porters.html for info).
13 This document describes differences between the 5.005 release and this one.
15 =head1 Incompatible Changes
17 =head2 Perl Source Incompatibilities
19 Beware that any new warnings that have been added or old ones
20 that have been enhanced are B<not> considered incompatible changes.
22 Since all new warnings must be explicitly requested via the C<-w>
23 switch or the C<warnings> pragma, it is ultimately the programmer's
24 responsibility to ensure that warnings are enabled judiciously.
28 =item CHECK is a new keyword
30 In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
31 subroutines named C<CHECK> are now special. These are queued up during
32 compilation and behave similar to END blocks, except they are called at
33 the end of compilation rather than at the end of execution. They cannot
36 =item Treatment of list slices of undef has changed
38 When taking a slice of a literal list (as opposed to a slice of
39 an array or hash), Perl used to return an empty list if the
40 result happened to be composed of all undef values.
42 The new behavior is to produce an empty list if (and only if)
43 the original list was empty. Consider the following example:
45 @a = (1,undef,undef,2)[2,1,2];
47 The old behavior would have resulted in @a having no elements.
48 The new behavior ensures it has three undefined elements.
50 Note in particular that the behavior of slices of the following
51 cases remains unchanged:
55 @a = (anything_returning_empty_list())[2,1,2];
61 =head2 Perl's version numbering has changed
63 Beginning with Perl version 5.6, the version number convention has been
64 changed to a "dotted integer" scheme that is more commonly found in open
67 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
68 The next development series following v5.6 will be numbered v5.7.x,
69 beginning with v5.7.0, and the next major production release following
72 The English module now sets $PERL_VERSION to $^V (a string value) rather
73 than C<$]> (a numeric value). (This is a potential incompatibility.
74 Send us a report via perlbug if you are affected by this.)
76 The v1.2.3 syntax is also now legal in Perl.
77 See L<Support for strings represented as a vector of ordinals> for more on that.
79 To cope with the new versioning system's use of at least three significant
80 digits for each version component, the method used for incrementing the
81 subversion number has also changed slightly. We assume that versions older
82 than v5.6 have been incrementing the subversion component in multiples of
83 10. Versions after v5.6.0 will increment them by 1. Thus, using the new
84 notation, 5.005_03 is the same as v5.5.30, and the first maintenance
85 version following v5.6.0 will be v5.6.1, which amounts to a floating point
88 =item Literals of the form C<1.2.3> parse differently
90 Previously, numeric literals with more than one dot in them were
91 interpreted as a floating point number concatenated with one or more
92 numbers. Such "numbers" are now parsed as strings composed of the
95 For example, C<print 97.98.99> used to output C<97.9899> in earlier
96 versions, but now prints C<abc>.
98 See L<Support for strings represented as a vector of ordinals> below.
100 =item Possibly changed pseudo-random number generator
102 In 5.005_0x and earlier, perl's rand() function used the C library
103 rand(3) function. As of 5.005_52, Configure tests for drand48(),
104 random(), and rand() (in that order) and picks the first one it finds.
105 Perl programs that depend on reproducing a specific set of pseudo-random
106 numbers will now likely produce different output. You can use
107 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
109 =item Hashing function for hash keys has changed
111 Perl hashes are not order preserving. The apparently random order
112 encountered when iterating on the contents of a hash is determined
113 by the hashing algorithm used. To improve the distribution of lower
114 bits in the hashed value, the algorithm has changed slightly as of
115 5.005_52. When iterating over hashes, this may yield a random order
116 that is B<different> from that of previous versions.
118 =item C<undef> fails on read only values
120 Using the C<undef> operator on a readonly value (such as $1) has
121 the same effect as assigning C<undef> to the readonly value--it
124 =item Close-on-exec bit may be set on pipe and socket handles
126 On systems that support a close-on-exec flag on filehandles, the
127 flag will be set for any handles created by pipe(), socketpair(),
128 socket(), and accept(), if that is warranted by the value of $^F
129 that may be in effect. Earlier versions neglected to set the flag
130 for handles created with these operators. See L<perlfunc/pipe>,
131 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
134 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
136 Perl 5.004 deprecated the interpretation of C<$$1> and
137 similar within interpolated strings to mean C<$$ . "1">,
138 but still allowed it.
140 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
142 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
144 delete(), each(), values() and hashes in a list context return the actual
145 values in the hash, instead of copies (as they used to in earlier
146 versions). Typical idioms for using these constructs copy the
147 returned values, but this can make a significant difference when
148 creating references to the returned values.
150 Keys in the hash are still returned as copies when iterating on
153 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
155 vec() generates a run-time error if the BITS argument is not
156 a valid power-of-two integer.
158 =item Text of some diagnostic output has changed
160 Most references to internal Perl operations in diagnostics
161 have been changed to be more descriptive. This may be an
162 issue for programs that may incorrectly rely on the exact
163 text of diagnostics for proper functioning.
165 =item C<%@> has been removed
167 The undocumented special variable C<%@> that used to accumulate
168 "background" errors (such as those that happen in DESTROY())
169 has been removed, because it could potentially result in memory
172 =item Parenthesized not() behaves like a list operator
174 The C<not> operator now falls under the "if it looks like a function,
175 it behaves like a function" rule.
177 As a result, the parenthesized form can be used with C<grep> and C<map>.
178 The following construct used to be a syntax error before, but it works
181 grep not($_), @things;
183 On the other hand, using C<not> with a literal list slice may not
184 work. The following previously allowed construct:
186 print not (1,2,3)[0];
188 needs to be written with additional parentheses now:
190 print not((1,2,3)[0]);
192 The behavior remains unaffected when C<not> is not followed by parentheses.
194 =item Semantics of bareword prototype C<(*)> have changed
196 Arguments prototyped as C<*> will now be visible within the subroutine
197 as either a simple scalar or as a reference to a typeglob. Perl 5.005
198 always coerced simple scalar arguments to a typeglob, which wasn't useful
199 in situations where the subroutine must distinguish between a simple
200 scalar and a typeglob. See L<perlsub/Prototypes>.
204 =head2 C Source Incompatibilities
208 =item C<PERL_POLLUTE>
210 Release 5.005 grandfathered old global symbol names by providing preprocessor
211 macros for extension source compatibility. As of release 5.6, these
212 preprocessor definitions are not available by default. You need to explicitly
213 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
214 extensions still using the old symbols, this option can be
215 specified via MakeMaker:
217 perl Makefile.PL POLLUTE=1
219 =item C<PERL_IMPLICIT_CONTEXT>
221 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
222 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
223 intended to be enabled by users at this time.
225 This new build option provides a set of macros for all API functions
226 such that an implicit interpreter/thread context argument is passed to
227 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
228 amounts to a macro invocation that actually translates to something like
229 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
230 to not have any significant source compatibility issues, the difference
231 between a macro and a real function call will need to be considered.
233 This means that there B<is> a source compatibility issue as a result of
234 this if your extensions attempt to use pointers to any of the Perl API
237 Note that the above issue is not relevant to the default build of
238 Perl, whose interfaces continue to match those of prior versions
239 (but subject to the other options described here).
241 See L<perlguts/"The Perl API"> for detailed information on the
242 ramifications of building Perl using this option.
244 =item C<PERL_POLLUTE_MALLOC>
246 Enabling Perl's malloc in release 5.005 and earlier caused
247 the namespace of system versions of the malloc family of functions to
248 be usurped by the Perl versions, since by default they used the
251 Besides causing problems on platforms that do not allow these functions to
252 be cleanly replaced, this also meant that the system versions could not
253 be called in programs that used Perl's malloc. Previous versions of Perl
254 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
255 EMBEDMYMALLOC preprocessor definitions.
257 As of release 5.6, Perl's malloc family of functions have default names
258 distinct from the system versions. You need to explicitly compile perl with
259 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
260 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
263 Note that these functions do B<not> constitute Perl's memory allocation API.
264 See L<perlguts/"Memory Allocation"> for further information about that.
268 =head2 Compatible C Source API Changes
272 =item C<PATCHLEVEL> is now C<PERL_VERSION>
274 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
275 are now available by default from perl.h, and reflect the base revision,
276 patchlevel, and subversion respectively. C<PERL_REVISION> had no
277 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
278 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
280 The new names cause less pollution of the B<cpp> namespace and reflect what
281 the numbers have come to stand for in common practice. For compatibility,
282 the old names are still supported when F<patchlevel.h> is explicitly
283 included (as required before), so there is no source incompatibility
286 =item Support for C++ exceptions
288 change#3386, also needs perlguts documentation
289 [TODO - Chip Salzenberg <chip@perlsupport.com>]
293 =head2 Binary Incompatibilities
295 In general, the default build of this release is expected to be binary
296 compatible for extensions built with the 5.005 release or its maintenance
297 versions. However, specific platforms may have broken binary compatibility
298 due to changes in the defaults used in hints files. Therefore, please be
299 sure to always check the platform-specific README files for any notes to
302 The usethreads or usemultiplicity builds are B<not> binary compatible
303 with the corresponding builds in 5.005.
305 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
306 among others), purely internal symbols such as parser functions and the
307 run time opcodes are not exported by default. Perl 5.005 used to export
308 all functions irrespective of whether they were considered part of the
311 For the full list of public API functions, see L<perlapi>.
313 =head1 Installation and Configuration Improvements
315 =head2 -Dusethreads means something different
317 WARNING: Support for threads continues to be an experimental feature.
318 Interfaces and implementation are subject to sudden and drastic changes.
320 The -Dusethreads flag now enables the experimental interpreter-based thread
321 support by default. To get the flavor of experimental threads that was in
322 5.005 instead, you need to ask for -Duse5005threads.
324 As of v5.5.640, interpreter-threads support is still lacking a way to
325 create new threads from Perl (i.e., C<use Thread;> will not work with
326 interpreter threads). C<use Thread;> continues to be available when you
327 ask for -Duse5005threads, bugs and all.
329 =head2 New Configure flags
331 The following new flags may be enabled on the Configure command line
332 by running Configure with C<-Dflag>.
337 use64bitint (equal to now deprecated 'use64bits')
343 usesocks (only SOCKS v5 supported)
345 =head2 Threadedness and 64-bitness now more daring
347 The Configure options enabling the use of threads and the use of
348 64-bitness are now more daring in the sense that they no more have an
349 explicit list of operating systems of known threads/64-bit
350 capabilities. In other words: if your operating system has the
351 necessary APIs and datatypes, you should be able just to go ahead and
352 use them, for threads by Configure -Dusethreads, and for 64 bits
353 either explicitly by Configure -Duse64bitint or implicitly if your
354 system has 64 bit wide datatypes. See also L<"64-bit support">.
358 Some platforms have "long doubles", floating point numbers of even
359 larger range than ordinary "doubles". To enable using long doubles for
360 Perl's scalars, use -Duselongdouble.
364 You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
365 See also L<"64-bit support">.
367 =head2 -Duselargefiles
369 Some platforms support large files, files larger than two gigabytes.
370 See L<"Large file support"> for more information.
372 =head2 installusrbinperl
374 You can use "Configure -Uinstallusrbinperl" which causes installperl
375 to skip installing perl also as /usr/bin/perl. This is useful if you
376 prefer not to modify /usr/bin for some reason or another but harmful
377 because many scripts assume to find Perl in /usr/bin/perl.
381 You can use "Configure -Dusesocks" which causes Perl to probe
382 for the SOCKS (v5, not v4) proxy protocol library,
383 http://www.socks.nec.com/
387 You can "post-edit" the Configure variables using the Configure C<-A>
388 flag. The editing happens immediately after the platform specific
389 hints files have been processed but before the actual configuration
390 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
392 =head2 Enhanced Installation Directories
394 The installation structure has been enriched to improve the support
395 for maintaining multiple versions of perl, to provide locations for
396 vendor-supplied modules, scripts, and manpages, and to ease maintenance
397 of locally-added modules, scripts, and manpages. See the section on
398 Installation Directories in the INSTALL file for complete details.
399 For most users building and installing from source, the defaults should
402 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
403 special values for library directories, you might wish to consider using
404 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
405 config.sh file from an earlier version of perl, you should be sure to
406 check that Configure makes sensible choices for the new directories.
407 See INSTALL for complete details.
411 =head2 Unicode and UTF-8 support
413 Perl can optionally use UTF-8 as its internal representation for character
414 strings. The C<utf8> and C<bytes> pragmas are used to control this support
415 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
418 =head2 Interpreter cloning, threads, and concurrency
420 WARNING: This is an experimental feature in a pre-alpha state. Use
423 Perl 5.005_63 introduces the beginnings of support for running multiple
424 interpreters concurrently in different threads. In conjunction with
425 the perl_clone() API call, which can be used to selectively duplicate
426 the state of any given interpreter, it is possible to compile a
427 piece of code once in an interpreter, clone that interpreter
428 one or more times, and run all the resulting interpreters in distinct
431 On Windows, this feature is used to emulate fork() at the interpreter
432 level. See L<perlfork>.
434 This feature is still in evolution. It is eventually meant to be used
435 to selectively clone a subroutine and data reachable from that
436 subroutine in a separate interpreter and run the cloned subroutine
437 in a separate thread. Since there is no shared data between the
438 interpreters, little or no locking will be needed (unless parts of
439 the symbol table are explicitly shared). This is obviously intended
440 to be an easy-to-use replacement for the existing threads support.
442 Support for cloning interpreters and interpreter concurrency can be
443 enabled using the -Dusethreads Configure option (see win32/Makefile for
444 how to enable it on Windows.) The resulting perl executable will be
445 functionally identical to one that was built with -Dmultiplicity, but
446 the perl_clone() API call will only be available in the former.
448 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
449 Perl source code changes that provide a clear separation between the op tree
450 and the data it operates with. The former is considered immutable, and can
451 therefore be shared between an interpreter and all of its clones, while the
452 latter is considered local to each interpreter, and is therefore copied for
455 Note that building Perl with the -Dusemultiplicity Configure option
456 is adequate if you wish to run multiple B<independent> interpreters
457 concurrently in different threads. -Dusethreads only provides the
458 additional functionality of the perl_clone() API call and other
459 support for running B<cloned> interpreters concurrently.
461 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
464 =head2 Lexically scoped warning categories
466 You can now control the granularity of warnings emitted by perl at a finer
467 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
470 =head2 Lvalue subroutines
472 WARNING: This is an experimental feature.
475 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
476 Tuomas Lukka <lukka@iki.fi>)]
478 =head2 "our" declarations
480 An "our" declaration introduces a value that can be best understood
481 as a lexically scoped symbolic alias to a global variable in the
482 package that was current where the variable was declared. This is
483 mostly useful as an alternative to the C<vars> pragma, but also provides
484 the opportunity to introduce typing and other attributes for such
485 variables. See L<perlfunc/our>.
487 =head2 Support for strings represented as a vector of ordinals
489 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
490 of characters with the specified ordinals. This is an alternative, more
491 readable way to construct (possibly unicode) strings instead of
492 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
493 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
494 parsed the same as C<v1.2.3>.
496 Strings written in this form are also useful to represent version "numbers".
497 It is easy to compare such version "numbers" (which are really just plain
498 strings) using any of the usual string comparison operators C<eq>, C<ne>,
499 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
502 In conjunction with the new C<$^V> magic variable (which contains
503 the perl version as a string), such literals can be used as a readable way
504 to check if you're running a particular version of Perl:
506 # this will parse in older versions of Perl also
507 if ($^V and $^V gt v5.5.640) {
508 # new features supported
511 C<require> and C<use> also have some special magic to support such literals.
512 They will be interpreted as a version rather than as a module name:
514 require v5.6.0; # croak if $^V lt v5.6.0
515 use v5.6.0; # same, but croaks at compile-time
517 Alternatively, the C<v> may be omitted if there is more than one dot:
522 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
523 to print ordinals of characters in arbitrary strings:
525 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
526 printf "%*vX", ":", $addr; # formats IPv6 address
527 printf "%*vb", " ", $bits; # displays bitstring
529 See L<perlop/"Strings of Character"> for additional information.
531 =head2 Weak references
533 WARNING: This is an experimental feature.
535 In previous versions of Perl, you couldn't cache objects so as
536 to allow them to be deleted if the last reference from outside
537 the cache is deleted. The reference in the cache would hold a
538 reference count on the object and the objects would never be
541 Another familiar problem is with circular references. When an
542 object references itself, its reference count would never go
543 down to zero, and it would not get destroyed until the program
546 Weak references solve this by allowing you to "weaken" any
547 reference, that is, make it not count towards the reference count.
548 When the last non-weak reference to an object is deleted, the object
549 is destroyed and all the weak references to the object are
550 automatically undef-ed.
552 To use this feature, you need the WeakRef package from CPAN, which
553 contains additional documentation.
555 change#3385, also need perlguts documentation
556 [TODO - Tuomas Lukka <lukka@iki.fi>]
558 =head2 File globbing implemented internally
560 WARNING: This is currently an experimental feature. Interfaces and
561 implementation are likely to change.
563 Perl now uses the File::Glob implementation of the glob() operator
564 automatically. This avoids using an external csh process and the
565 problems associated with it.
567 =head2 Binary numbers supported
569 Binary numbers are now supported as literals, in s?printf formats, and
573 printf "The answer is: %b\n", oct("0b101010");
575 =head2 Some arrows may be omitted in calls through references
577 Perl now allows the arrow to be omitted in many constructs
578 involving subroutine calls through references. For example,
579 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
580 This is rather similar to how the arrow may be omitted from
581 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
582 required for C<foo(10)-E<gt>('bar')>.
584 =head2 exists() is supported on subroutine names
586 The exists() builtin now works on subroutine names. A subroutine
587 is considered to exist if it has been declared (even if implicitly).
588 See L<perlfunc/exists> for examples.
590 =head2 exists() and delete() are supported on array elements
592 The exists() and delete() builtins now work on simple arrays as well.
593 The behavior is similar to that on hash elements.
595 exists() can be used to check whether an array element has been
596 initialized. This avoids autovivifying array elements that don't exist.
597 If the array is tied, the EXISTS() method in the corresponding tied
598 package will be invoked.
600 delete() may be used to remove an element from the array and return
601 it. The array element at that position returns to its unintialized
602 state, so that testing for the same element with exists() will return
603 false. If the element happens to be the one at the end, the size of
604 the array also shrinks up to the highest element that tests true for
605 exists(), or 0 if none such is found. If the array is tied, the DELETE()
606 method in the corresponding tied package will be invoked.
608 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
610 =head2 syswrite() ease-of-use
612 The length argument of C<syswrite()> has become optional.
614 =head2 File and directory handles can be autovivified
616 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
617 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
618 socket(), and accept()) now autovivify a file or directory handle
619 if the handle passed to them is an uninitialized scalar variable. This
620 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
621 to be used to create filehandles that will conveniently be closed
622 automatically when the scope ends, provided there are no other references
623 to them. This largely eliminates the need for typeglobs when opening
624 filehandles that must be passed around, as in the following example:
628 or die "Can't open '@_': $!";
633 my $f = myopen("</etc/motd");
635 # $f implicitly closed here
638 [TODO - this idiom needs more pod penetration]
640 =head2 64-bit support
642 NOTE: The Configure flags -Duselonglong and -Duse64bits
643 have been deprecated. Use -Duse64bitint instead.
645 Any platform that has 64-bit integers either (a) natively as longs or
646 ints (b) via special compiler flags (c) using long long are able to
647 use "quads" (64-integers) as follows:
653 constants (decimal, hexadecimal, octal, binary) in the code
657 arguments to oct() and hex()
661 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
669 pack() and unpack() "q" and "Q" formats
673 in basic arithmetics: + - * / % (NOTE: operating close to the limits
674 of the integer values may produce surprising results)
678 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
687 Note that unless you have the case (a) you will have to configure
688 and compile Perl using the -Duse64bitint Configure flag.
690 There are actually two modes of 64-bitness: the first one is achieved
691 using Configure -Duse64bitint and the second one using Configure
692 -Duse64bitall. The difference is that the first one is minimal and
693 the second one maximal. The first one does only as much as is
694 required to get 64-bit integers into Perl (this may mean, for example,
695 using "long longs") while your memory may still be limited to 2
696 gigabytes (because your pointers most likely are 32-bit); the second
697 one goes all the way by attempting to switch also longs (and pointers)
698 being 64-bit. This may create an even more binary incompatible Perl
699 than -Duse64bitint: the resulting executable may not run at all in a
700 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
701 operating system to be 64-bit aware.
703 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
706 Last but not least: note that due to Perl's habit of always using
707 floating point numbers the quads are still not true integers.
708 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
709 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
710 are silently promoted to floating point numbers, after which they will
711 start losing precision (their lower digits).
713 =head2 Large file support
715 If you have filesystems that support "large files" (files larger than
716 2 gigabytes), you may now also be able to create and access them from
717 Perl. You have to use Configure -Duselargefiles. Turning on the
718 large file support turns on also the 64-bit support on many platforms.
719 Beware that unless your filesystem also supports "sparse files" seeking
720 to umpteen petabytes may be unadvisable.
722 Note that in addition to requiring a proper file system to do large
723 files you may also need to adjust your per-process (or your
724 per-system, or per-process-group, or per-user-group) maximum filesize
725 limits before running Perl scripts that try to handle large files,
726 especially if you intend to write such files.
728 Finally, in addition to your process/process group maximum filesize
729 limits, you may have quota limits on your filesystems that stop you
730 (your user id or your user group id) from using large files.
732 Adjusting your process/user/group/file system/operating system limits
733 is outside the scope of Perl core language. For process limits, you
734 may try increasing the limits using your shell's limits/limit/ulimit
735 command before running Perl. The BSD::Resource extension (not
736 included with the standard Perl distribution) may also be of use, it
737 offers the getrlimit/setrlimit interface that can be used to adjust
738 process resource usage limits, including the maximum filesize limit.
742 In some systems you may be able to use long doubles to enhance the
743 range and precision of your double precision floating point numbers
744 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
745 this support (if it is available).
749 You can "Configure -Dusemorebits" to turn on both the 64-bit support
750 and the long double support.
752 =head2 Enhanced support for sort() subroutines
754 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
755 now be used as sort subroutines. In either case, the two elements to
756 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
758 For unprototyped sort subroutines, the historical behavior of passing
759 the elements to be compared as the global variables $a and $b remains
762 =head2 Better syntax checks on parenthesized unary operators
766 print defined(&foo,&bar,&baz);
767 print uc("foo","bar","baz");
770 used to be accidentally allowed in earlier versions, and produced
771 unpredictable behaviour. Some produced ancillary warnings
772 when used in this way; others silently did the wrong thing.
774 The parenthesized forms of most unary operators that expect a single
775 argument now ensure that they are not called with more than one
776 argument, making the cases shown above syntax errors. The usual
779 print defined &foo, &bar, &baz;
780 print uc "foo", "bar", "baz";
783 remains unchanged. See L<perlop>.
785 =head2 POSIX character class syntax [: :] supported
787 For example to match alphabetic characters use /[[:alpha:]]/.
788 See L<perlre> for details.
790 =head2 Improved C<qw//> operator
792 The C<qw//> operator is now evaluated at compile time into a true list
793 instead of being replaced with a run time call to C<split()>. This
794 removes the confusing misbehaviour of C<qw//> in scalar context, which
795 had inherited that behaviour from split().
799 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
801 now correctly prints "3|a", instead of "2|a".
803 =head2 pack() format 'Z' supported
805 The new format type 'Z' is useful for packing and unpacking null-terminated
806 strings. See L<perlfunc/"pack">.
808 =head2 pack() format modifier '!' supported
810 The new format type modifier '!' is useful for packing and unpacking
811 native shorts, ints, and longs. See L<perlfunc/"pack">.
813 =head2 pack() and unpack() support counted strings
815 The template character '/' can be used to specify a counted string
816 type to be packed or unpacked. See L<perlfunc/"pack">.
818 =head2 Comments in pack() templates
820 The '#' character in a template introduces a comment up to
821 end of the line. This facilitates documentation of pack()
824 =head2 $^X variables may now have names longer than one character
826 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
827 error. Now variable names that begin with a control character may be
828 arbitrarily long. However, for compatibility reasons, these variables
829 I<must> be written with explicit braces, as C<${^XY}> for example.
830 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
831 than one control character, such as C<${^XY^Z}>, are illegal.
833 The old syntax has not changed. As before, `^X' may be either a
834 literal control-X character or the two-character sequence `caret' plus
835 `X'. When braces are omitted, the variable name stops after the
836 control character. Thus C<"$^XYZ"> continues to be synonymous with
837 C<$^X . "YZ"> as before.
839 As before, lexical variables may not have names beginning with control
840 characters. As before, variables whose names begin with a control
841 character are always forced to be in package `main'. All such variables
842 are reserved for future extensions, except those that begin with
843 C<^_>, which may be used by user programs and are guaranteed not to
844 acquire special meaning in any future version of Perl.
846 =head2 C<use attrs> implicit in subroutine attributes
848 Formerly, if you wanted to mark a subroutine as being a method call or
849 as requiring an automatic lock() when it is entered, you had to declare
850 that with a C<use attrs> pragma in the body of the subroutine.
851 That can now be accomplished with declaration syntax, like this:
853 sub mymethod : locked method ;
855 sub mymethod : locked method {
859 sub othermethod :locked :method ;
861 sub othermethod :locked :method {
866 (Note how only the first C<:> is mandatory, and whitespace surrounding
867 the C<:> is optional.)
869 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
870 with the stubs they provide. See L<attributes>.
872 =head2 Regular expression improvements
874 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
875 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
877 =head2 Overloading improvements
880 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
882 =head2 open() with more than two arguments
884 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
886 =head2 Support for interpolating named characters
889 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
891 =head2 Experimental support for user-hooks in @INC
893 [TODO - Ken Fox <kfox@ford.com>]
895 =head2 C<require> and C<do> may be overridden
897 C<require> and C<do 'file'> operations may be overridden locally
898 by importing subroutines of the same name into the current package
899 (or globally by importing them into the CORE::GLOBAL:: namespace).
900 Overriding C<require> will also affect C<use>, provided the override
901 is visible at compile-time.
902 See L<perlsub/"Overriding Built-in Functions">.
904 =head2 New variable $^C reflects C<-c> switch
906 C<$^C> has a boolean value that reflects whether perl is being run
907 in compile-only mode (i.e. via the C<-c> switch). Since
908 BEGIN blocks are executed under such conditions, this variable
909 enables perl code to determine whether actions that make sense
910 only during normal running are warranted. See L<perlvar>.
912 =head2 New variable $^V contains Perl version in v5.6.0 format
914 C<$^V> contains the Perl version number as a string composed of
915 characters whose ordinals match the version numbers, so that it may
916 be used in string comparisons.
918 See C<Support for strings represented as a vector of ordinals> for an
921 =head2 Optional Y2K warnings
923 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
924 it emits optional warnings when concatenating the number 19
927 This behavior must be specifically enabled when running Configure.
928 See F<INSTALL> and F<README.Y2K>.
930 =head1 Significant bug fixes
932 =head2 E<lt>HANDLEE<gt> on empty files
934 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
935 zero length (instead of C<undef>, as it used to) the first time the
936 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
939 This means that the following will append "foo" to an empty file (it used
942 perl -0777 -pi -e 's/^/foo/' empty_file
946 perl -pi -e 's/^/foo/' empty_file
948 is unchanged (it continues to leave the file empty).
950 =head2 C<eval '...'> improvements
952 Line numbers (as reflected by caller() and most diagnostics) within
953 C<eval '...'> were often incorrect when here documents were involved.
954 This has been corrected.
956 Lexical lookups for variables appearing in C<eval '...'> within
957 functions that were themselves called within an C<eval '...'> were
958 searching the wrong place for lexicals. The lexical search now
959 correctly ends at the subroutine's block boundary.
961 Parsing of here documents used to be flawed when they appeared as
962 the replacement expression in C<eval 's/.../.../e'>. This has
965 =head2 All compilation errors are true errors
967 Some "errors" encountered at compile time were by neccessity
968 generated as warnings followed by eventual termination of the
969 program. This enabled more such errors to be reported in a
970 single run, rather than causing a hard stop at the first error
971 that was encountered.
973 The mechanism for reporting such errors has been reimplemented
974 to queue compile-time errors and report them at the end of the
975 compilation as true errors rather than as warnings. This fixes
976 cases where error messages leaked through in the form of warnings
977 when code was compiled at run time using C<eval STRING>, and
978 also allows such errors to be reliably trapped using __DIE__ hooks.
980 =head2 Automatic flushing of output buffers
982 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
983 of all files opened for output when the operation
984 was attempted. This mostly eliminates confusing
985 buffering mishaps suffered by users unaware of how Perl internally
988 =head2 Better diagnostics on meaningless filehandle operations
990 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
991 are compile time errors. Attempting to read from filehandles that
992 were opened only for writing will now produce warnings (just as
993 writing to read-only filehandles does).
995 =head2 Where possible, buffered data discarded from duped input filehandle
997 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
998 was previously read and buffered in C<OLD> before duping the handle.
999 On platforms where doing this is allowed, the next read operation
1000 on C<NEW> will return the same data as the corresponding operation
1001 on C<OLD>. Formerly, it would have returned the data from the start
1002 of the following disk block instead.
1004 =head2 eof() has the same old magic as <>
1006 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
1007 yet been made. C<eof()> has been changed to have a little magic of its
1008 own, it now opens the C<E<lt>E<gt>> files.
1010 =head2 system(), backticks and pipe open now reflect exec() failure
1012 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1013 etc., are implemented via fork() and exec(). When the underlying
1014 exec() fails, earlier versions did not report the error properly,
1015 since the exec() happened to be in a different process.
1017 The child process now communicates with the parent about the
1018 error in launching the external command, which allows these
1019 constructs to return with their usual error value and set $!.
1021 =head2 Implicitly closed filehandles are safer
1023 Sometimes implicitly closed filehandles (as when they are localized,
1024 and Perl automatically closes them on exiting the scope) could
1025 inadvertently set $? or $!. This has been corrected.
1027 =head2 C<(\$)> prototype and C<$foo{a}>
1029 An scalar reference prototype now correctly allows a hash or
1030 array element in that slot.
1032 =head2 Pseudo-hashes work better
1034 Dereferencing some types of reference values in a pseudo-hash,
1035 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
1038 When applied to a pseudo-hash element, exists() now reports whether
1039 the specified value exists, not merely if the key is valid.
1041 delete() now works on pseudo-hashes. When given a pseudo-hash element
1042 or slice it deletes the values corresponding to the keys (but not the keys
1043 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1045 Pseudo-hash slices with constant keys are now optimized to array lookups
1048 The C<fields> pragma now provides ways to create pseudo-hashes, via
1049 fields::new() and fields::phash(). See L<fields>.
1051 =head2 C<goto &sub> and AUTOLOAD
1053 The C<goto &sub> construct works correctly when C<&sub> happens
1056 =head2 C<-bareword> allowed under C<use integer>
1058 The autoquoting of barewords preceded by C<-> did not work
1059 in prior versions when the C<integer> pragma was enabled.
1060 This has been fixed.
1062 =head2 Boolean assignment operators are legal lvalues
1064 Constructs such as C<($a ||= 2) += 1> are now allowed.
1066 =head2 C<sort $coderef @foo> allowed
1068 sort() did not accept a subroutine reference as the comparison
1069 function in earlier versions. This is now permitted.
1071 =head2 Failures in DESTROY()
1073 When code in a destructor threw an exception, it went unnoticed
1074 in earlier versions of Perl, unless someone happened to be
1075 looking in $@ just after the point the destructor happened to
1076 run. Such failures are now visible as warnings when warnings are
1079 =head2 Locale bugs fixed
1081 printf() and sprintf() previously reset the numeric locale
1082 back to the default "C" locale. This has been fixed.
1084 Numbers formatted according to the local numeric locale
1085 (such as using a decimal comma instead of a decimal dot) caused
1086 "isn't numeric" warnings, even while the operations accessing
1087 those numbers produced correct results. The warnings are gone.
1091 The C<eval 'return sub {...}'> construct could sometimes leak
1092 memory. This has been fixed.
1094 Operations that aren't filehandle constructors used to leak memory
1095 when used on invalid filehandles. This has been fixed.
1097 Constructs that modified C<@_> could fail to deallocate values
1098 in C<@_> and thus leak memory. This has been corrected.
1100 =head2 Spurious subroutine stubs after failed subroutine calls
1102 Perl could sometimes create empty subroutine stubs when a
1103 subroutine was not found in the package. Such cases stopped
1104 later method lookups from progressing into base packages.
1105 This has been corrected.
1107 =head2 Consistent numeric conversions
1110 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1112 =head2 Taint failures under C<-U>
1114 When running in unsafe mode, taint violations could sometimes
1115 cause silent failures. This has been fixed.
1117 =head2 END blocks and the C<-c> switch
1119 Prior versions used to run BEGIN B<and> END blocks when Perl was
1120 run in compile-only mode. Since this is typically not the expected
1121 behavior, END blocks are not executed anymore when the C<-c> switch
1124 See L<CHECK blocks> for how to run things when the compile phase ends.
1126 =head2 Potential to leak DATA filehandles
1128 Using the C<__DATA__> token creates an implicit filehandle to
1129 the file that contains the token. It is the program's
1130 responsibility to close it when it is done reading from it.
1132 This caveat is now better explained in the documentation.
1135 =head2 Diagnostics follow STDERR
1137 Diagnostic output now goes to whichever file the C<STDERR> handle
1138 is pointing at, instead of always going to the underlying C runtime
1139 library's C<stderr>.
1141 =head2 Other fixes for better diagnostics
1143 Line numbers are no longer suppressed (under most likely circumstances)
1144 during the global destruction phase.
1146 Diagnostics emitted from code running in threads other than the main
1147 thread are now accompanied by the thread ID.
1149 Embedded null characters in diagnostics now actually show up. They
1150 used to truncate the message in prior versions.
1152 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1153 if sort() is encountered in package foo.
1155 Unrecognized alphabetic escapes encountered when parsing quote
1156 constructs now generate a warning, since they may take on new
1157 semantics in later versions of Perl.
1159 =head1 Performance enhancements
1161 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1163 Many common sort() operations using a simple inlined block are now
1164 optimized for faster performance.
1166 =head2 Optimized assignments to lexical variables
1168 Certain operations in the RHS of assignment statements have been
1169 optimized to directly set the lexical variable on the LHS,
1170 eliminating redundant copying overheads.
1172 =head2 Method lookups optimized
1174 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1176 =head2 Faster mechanism to invoke XSUBs
1179 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1181 =head2 Perl_malloc() improvements
1184 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1186 =head2 Faster subroutine calls
1188 Minor changes in how subroutine calls are handled internally
1189 provide marginal improvements in performance.
1191 =head1 Platform specific changes
1193 =head2 Additional supported platforms
1199 VM/ESA is now supported.
1203 Siemens BS2000 is now supported under the POSIX Shell.
1207 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1212 GNU/Hurd is now supported.
1216 Rhapsody is now supported.
1220 EPOC is is now supported (on Psion 5).
1230 Perl now works with djgpp 2.02 (and 2.03 alpha).
1234 Environment variable names are not converted to uppercase any more.
1238 Wrong exit code from backticks now fixed.
1242 This port is still using its own builtin globbing.
1248 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1252 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1256 Site library searches failed to look for ".../site/5.XXX/lib"
1257 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1259 When given a pathname that consists only of a drivename, such
1260 as C<A:>, opendir() and stat() now use the current working
1261 directory for the drive rather than the drive root.
1263 The builtin XSUB functions in the Win32:: namespace are
1264 documented. See L<Win32>.
1266 $^X now contains the full path name of the running executable.
1268 A Win32::GetLongPathName() function is provided to complement
1269 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1271 POSIX::uname() is supported.
1273 system(1,...) now returns true process IDs rather than process
1274 handles. kill() accepts any real process id, rather than strictly
1275 return values from system(1,...).
1277 The C<Shell> module is supported.
1279 Rudimentary support for building under command.com in Windows 95
1282 Scripts are read in binary mode by default to allow ByteLoader (and
1283 the filter mechanism in general) to work properly. For compatibility,
1284 the DATA filehandle will be set to text mode if a carriage return is
1285 detected at the end of the line containing the __END__ or __DATA__
1286 token; if not, the DATA filehandle will be left open in binary mode.
1287 Earlier versions always opened the DATA filehandle in text mode.
1289 The glob() operator is implemented via the C<File::Glob> extension,
1290 which supports glob syntax of the C shell. This increases the flexibility
1291 of the glob() operator, but there may be compatibility issues for
1292 programs that relied on the older globbing syntax. If you want to
1293 preserve compatibility with the older syntax, you might want to put
1294 a C<use File::DosGlob;> in your program. For details and compatibility
1295 information, see L<File::Glob>.
1305 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1309 IO constants (SEEK_*, _IO*).
1313 Directory-related IO methods (new, read, close, rewind, tied delete).
1315 =item lib/io_multihomed
1317 INET sockets with multi-homed hosts.
1329 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1333 File test operators.
1337 Verify operations that access pad objects (lexicals and temporaries).
1341 Verify C<exists &sub> operations.
1345 =head1 Modules and Pragmata
1353 While used internally by Perl as a pragma, this module also
1354 provides a way to fetch subroutine and variable attributes.
1359 The Perl Compiler suite has been extensively reworked for this
1362 [TODO - Vishal Bhatia <vishal@gol.com>,
1363 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1367 The ByteLoader is a dedicated extension to generate and run
1368 Perl bytecode. See L<ByteLoader>.
1372 References can now be used.
1374 The new version also allows a leading underscore in constant names, but
1375 disallows a double leading underscore (as in "__LINE__"). Some other names
1376 are disallowed or warned against, including BEGIN, END, etc. Some names
1377 which were forced into main:: used to fail silently in some cases; now they're
1378 fatal (outside of main::) and an optional warning (inside of main::).
1379 The ability to detect whether a constant had been set with a given name has
1387 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1391 A C<Maxdepth> setting can be specified to avoid venturing
1392 too deeply into deep data structures. See L<Data::Dumper>.
1394 Dumping C<qr//> objects works correctly.
1398 C<DB> is an experimental module that exposes a clean abstraction
1399 to Perl's debugging API.
1403 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1404 See C<ext/DB_File/Changes>.
1408 Devel::DProf, a Perl source code profiler has been added. See
1409 L<Devel::DProf> and L<dprofpp>.
1413 The Dumpvalue module provides screen dumps of Perl data.
1417 Overall, Benchmark results exhibit lower average error and better timing
1420 You can now run tests for I<n> seconds instead of guessing the right
1421 number of tests to run: e.g. timethese(-5, ...) will run each
1422 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1423 means "for at least 3 CPU seconds". The output format has also
1424 changed. For example:
1426 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1428 will now output something like this:
1430 Benchmark: running a, b, each for at least 5 CPU seconds...
1431 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1432 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1434 New features: "each for at least N CPU seconds...", "wallclock secs",
1435 and the "@ operations/CPU second (n=operations)".
1437 timethese() now returns a reference to a hash of Benchmark objects containing
1438 the test results, keyed on the names of the tests.
1440 timethis() now returns the iterations field in the Benchmark result object
1443 timethese(), timethis(), and the new cmpthese() (see below) can also take
1444 a format specifier of 'none' to suppress output.
1446 A new function countit() is just like timeit() except that it takes a
1447 TIME instead of a COUNT.
1449 A new function cmpthese() prints a chart comparing the results of each test
1450 returned from a timethese() call. For each possible pair of tests, the
1451 percentage speed difference (iters/sec or seconds/iter) is shown.
1453 For other details, see L<Benchmark>.
1457 The Devel::Peek module provides access to the internal representation
1458 of Perl variables and data. It is a data debugging tool for the XS programmer.
1462 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1465 =item ExtUtils::MakeMaker
1467 change#4135, also needs docs in module pod
1468 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1472 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1473 large file (more than 4GB) access Note that the O_LARGEFILE is
1474 automatically/transparently added to sysopen() flags if large file
1475 support has been configured), Free/Net/OpenBSD locking behaviour flags
1476 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1477 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1478 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1479 The chmod()/stat() S_IF* constants and S_IS* functions are available
1480 via the C<:mode> tag.
1485 A compare_text() function has been added, which allows custom
1486 comparison functions. See L<File::Compare>.
1490 File::Find now works correctly when the wanted() function is either
1491 autoloaded or is a symbolic reference.
1493 A bug that caused File::Find to lose track of the working directory
1494 when pruning top-level directories has been fixed.
1496 File::Find now also supports several other options to control its
1497 behavior. It can follow symbolic links if the C<follow> option is
1498 specified. Enabling the C<no_chdir> option will make File::Find skip
1499 changing the current directory when walking directories. The C<untaint>
1500 flag can be useful when running with taint checks enabled.
1506 This extension implements BSD-style file globbing. By default,
1507 it will also be used for the internal implementation of the glob()
1508 operator. See L<File::Glob>.
1512 New methods have been added to the File::Spec module: devnull() returns
1513 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1514 the temp directory (normally /tmp on Unix). There are now also methods
1515 to convert between absolute and relative filenames: abs2rel() and
1516 rel2abs(). For compatibility with operating systems that specify volume
1517 names in file paths, the splitpath(), splitdir(), and catdir() methods
1520 =item File::Spec::Functions
1522 The new File::Spec::Functions modules provides a function interface
1523 to the File::Spec module. Allows shorthand
1525 $fullname = catfile($dir1, $dir2, $file);
1529 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1533 Getopt::Long licensing has changed to allow the Perl Artistic License
1534 as well as the GPL. It used to be GPL only, which got in the way of
1535 non-GPL applications that wanted to use Getopt::Long.
1537 Getopt::Long encourages the use of Pod::Usage to produce help
1538 messages. For example:
1544 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1545 pod2usage(1) if $help;
1546 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1552 sample - Using GetOpt::Long and Pod::Usage
1556 sample [options] [file ...]
1559 -help brief help message
1560 -man full documentation
1568 Print a brief help message and exits.
1572 Prints the manual page and exits.
1578 B<This program> will read the given input file(s) and do someting
1579 useful with the contents thereof.
1583 See L<Pod::Usage> for details.
1585 A bug that prevented the non-option call-back E<lt>E<gt> from being
1586 specified as the first argument has been fixed.
1588 To specify the characters E<lt> and E<gt> as option starters, use
1589 E<gt>E<lt>. Note, however, that changing option starters is strongly
1594 write() and syswrite() will now accept a single-argument
1595 form of the call, for consistency with Perl's syswrite().
1597 You can now create a TCP-based IO::Socket::INET without forcing
1598 a connect attempt. This allows you to configure its options
1599 (like making it non-blocking) and then call connect() manually.
1601 A bug that prevented the IO::Socket::protocol() accessor
1602 from ever returning the correct value has been corrected.
1606 Java Perl Lingo is now distributed with Perl. See jpl/README
1607 for more information.
1611 C<use lib> now weeds out any trailing duplicate entries.
1612 C<no lib> removes all named entries.
1616 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1617 and C<~> are now supported on bigints.
1621 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1622 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1626 A little bit of radial trigonometry (cylindrical and spherical),
1627 radial coordinate conversions, and the great circle distance were added.
1629 =item Pod::Parser, Pod::InputObjects
1631 Pod::Parser is a base class for parsing and selecting sections of
1632 pod documentation from an input stream. This module takes care of
1633 identifying pod paragraphs and commands in the input and hands off the
1634 parsed paragraphs and commands to user-defined methods which are free
1635 to interpret or translate them as they see fit.
1637 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1638 for advanced users of Pod::Parser that need more about a command besides
1641 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1642 "base parser code" recommended for use by all pod2xxx translators.
1643 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1644 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1645 underway. For any questions or comments about pod parsing and translating
1646 issues and utilities, please use the pod-people@perl.org mailing list.
1648 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1650 =item Pod::Checker, podchecker
1652 This utility checks pod files for correct syntax, according to
1653 L<perlpod>. Obvious errors are flagged as such, while warnings are
1654 printed for mistakes that can be handled gracefully. The checklist is
1655 not complete yet. See L<Pod::Checker>.
1657 =item Pod::ParseUtils, Pod::Find
1659 These modules provide a set of gizmos that are useful mainly for pod
1660 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1661 returns found pod files, along with their canonical names (like
1662 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1663 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1664 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1665 (for caching information about pod files, e.g. link nodes).
1667 =item Pod::Select, podselect
1669 Pod::Select is a subclass of Pod::Parser which provides a function
1670 named "podselect()" to filter out user-specified sections of raw pod
1671 documentation from an input stream. podselect is a script that provides
1672 access to Pod::Select from other scripts to be used as a filter.
1675 =item Pod::Usage, pod2usage
1677 Pod::Usage provides the function "pod2usage()" to print usage messages for
1678 a Perl script based on its embedded pod documentation. The pod2usage()
1679 function is generally useful to all script authors since it lets them
1680 write and maintain a single source (the pods) for documentation, thus
1681 removing the need to create and maintain redundant usage message text
1682 consisting of information already in the pods.
1684 There is also a pod2usage script which can be used from other kinds of
1685 scripts to print usage messages from pods (even for non-Perl scripts
1686 with pods embedded in comments).
1688 For details and examples, please see L<Pod::Usage>.
1690 =item Pod::Text and Pod::Man
1692 [TODO - Russ Allbery <rra@stanford.edu>]
1696 An EXISTS method has been added to this module (and sdbm_exists() has
1697 been added to the underlying sdbm library), so one can now call exists
1698 on an SDBM_File tied hash and get the correct result, rather than a
1701 A bug that may have caused data loss when more than one disk block
1702 happens to be read from the database in a single FETCH() has been
1707 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1708 no longer requires syslog.ph to exist.
1712 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1713 uname() if they exist.
1717 The timelocal() and timegm() functions used to silently return bogus
1718 results when the date fell outside the machine's integer range. They
1719 now consistently croak() if the date falls in an unsupported range.
1723 The error return value in list context has been changed for all functions
1724 that return a list of values. Previously these functions returned a list
1725 with a single element C<undef> if an error occurred. Now these functions
1726 return the empty list in these situations. This applies to the following
1732 The remaining functions are unchanged and continue to return C<undef> on
1733 error even in list context.
1735 The Win32::SetLastError(ERROR) function has been added as a complement
1736 to the Win32::GetLastError() function.
1738 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1739 pathname for FILENAME in scalar context. In list context it returns
1740 a two-element list containing the fully qualified directory name and
1741 the filename. See L<Win32>.
1745 A new feature called "DBM Filters" has been added to all the
1746 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1747 DBM Filters add four new methods to each DBM module:
1754 These can be used to filter key-value pairs before the pairs are
1755 written to the database or just after they are read from the database.
1756 See L<perldbmfilter> for further information.
1762 C<use attrs> is now obsolete, and is only provided for
1763 backward-compatibility. It's been replaced by the C<sub : attributes>
1764 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1766 C<use utf8> to enable UTF-8 and Unicode support.
1768 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1771 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1772 ...). Currently only one subpragma implemented, "use filetest
1773 'access';", that uses access(2) or equivalent to check permissions
1774 instead of using stat(2) as usual. This matters in filesystems
1775 where there are ACLs (access control lists): the stat(2) might lie,
1776 but access(2) knows better.
1778 =head1 Utility Changes
1782 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1786 C<perlcc> now supports the C and Bytecode backends. By default,
1787 it generates output from the simple C backend rather than the
1788 optimized C backend.
1790 Support for non-Unix platforms has been improved.
1795 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1797 =head1 Documentation Changes
1803 The official list of public Perl API functions.
1805 =item perlcompile.pod
1807 An introduction to using the Perl Compiler suite.
1809 =item perlfilter.pod
1811 An introduction to writing Perl source filters.
1815 Some guidelines for hacking the Perl source code.
1817 =item perlintern.pod
1819 A list of internal functions in the Perl source code.
1820 (List is currently empty.)
1822 =item perlopentut.pod
1824 A tutorial on using open() effectively.
1826 =item perlreftut.pod
1828 A tutorial that introduces the essentials of references.
1832 A tutorial on managing class data for object modules.
1834 =item perlunicode.pod
1836 An introduction to Unicode support features in Perl.
1840 =head1 New or Changed Diagnostics
1844 =item "%s" variable %s masks earlier declaration in same %s
1846 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1847 effectively eliminating all access to the previous instance. This is almost
1848 always a typographical error. Note that the earlier variable will still exist
1849 until the end of the scope or until all closure referents to it are
1852 =item "my sub" not yet implemented
1854 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1857 =item "our" variable %s redeclared
1859 (W) You seem to have already declared the same global once before in the
1860 current lexical scope.
1862 =item '!' allowed only after types %s
1864 (F) The '!' is allowed in pack() and unpack() only after certain types.
1865 See L<perlfunc/pack>.
1867 =item / cannot take a count
1869 (F) You had an unpack template indicating a counted-length string,
1870 but you have also specified an explicit size for the string.
1871 See L<perlfunc/pack>.
1873 =item / must be followed by a, A or Z
1875 (F) You had an unpack template indicating a counted-length string,
1876 which must be followed by one of the letters a, A or Z
1877 to indicate what sort of string is to be unpacked.
1878 See L<perlfunc/pack>.
1880 =item / must be followed by a*, A* or Z*
1882 (F) You had a pack template indicating a counted-length string,
1883 Currently the only things that can have their length counted are a*, A* or Z*.
1884 See L<perlfunc/pack>.
1886 =item / must follow a numeric type
1888 (F) You had an unpack template that contained a '#',
1889 but this did not follow some numeric unpack specification.
1890 See L<perlfunc/pack>.
1892 =item /%s/: Unrecognized escape \\%c passed through
1894 (W) You used a backslash-character combination which is not recognized
1895 by Perl. This combination appears in an interpolated variable or a
1896 C<'>-delimited regular expression. The character was understood literally.
1898 =item /%s/: Unrecognized escape \\%c in character class passed through
1900 (W) You used a backslash-character combination which is not recognized
1901 by Perl inside character classes. The character was understood literally.
1903 =item /%s/ should probably be written as "%s"
1905 (W) You have used a pattern where Perl expected to find a string,
1906 as in the first argument to C<join>. Perl will treat the true
1907 or false result of matching the pattern against $_ as the string,
1908 which is probably not what you had in mind.
1910 =item %s() called too early to check prototype
1912 (W) You've called a function that has a prototype before the parser saw a
1913 definition or declaration for it, and Perl could not check that the call
1914 conforms to the prototype. You need to either add an early prototype
1915 declaration for the subroutine in question, or move the subroutine
1916 definition ahead of the call to get proper prototype checking. Alternatively,
1917 if you are certain that you're calling the function correctly, you may put
1918 an ampersand before the name to avoid the warning. See L<perlsub>.
1920 =item %s argument is not a HASH or ARRAY element
1922 (F) The argument to exists() must be a hash or array element, such as:
1925 $ref->[12]->["susie"]
1927 =item %s argument is not a HASH or ARRAY element or slice
1929 (F) The argument to delete() must be either a hash or array element, such as:
1932 $ref->[12]->["susie"]
1934 or a hash or array slice, such as:
1936 @foo[$bar, $baz, $xyzzy]
1937 @{$ref->[12]}{"susie", "queue"}
1939 =item %s argument is not a subroutine name
1941 (F) The argument to exists() for C<exists &sub> must be a subroutine
1942 name, and not a subroutine call. C<exists &sub()> will generate this error.
1944 =item %s package attribute may clash with future reserved word: %s
1946 (W) A lowercase attribute name was used that had a package-specific handler.
1947 That name might have a meaning to Perl itself some day, even though it
1948 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1951 =item (in cleanup) %s
1953 (W) This prefix usually indicates that a DESTROY() method raised
1954 the indicated exception. Since destructors are usually called by
1955 the system at arbitrary points during execution, and often a vast
1956 number of times, the warning is issued only once for any number
1957 of failures that would otherwise result in the same message being
1960 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1961 could also result in this warning. See L<perlcall/G_KEEPERR>.
1963 =item <> should be quotes
1965 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1968 =item Attempt to join self
1970 (F) You tried to join a thread from within itself, which is an
1971 impossible task. You may be joining the wrong thread, or you may
1972 need to move the join() to some other thread.
1974 =item Bad evalled substitution pattern
1976 (F) You've used the /e switch to evaluate the replacement for a
1977 substitution, but perl found a syntax error in the code to evaluate,
1978 most likely an unexpected right brace '}'.
1980 =item Bad realloc() ignored
1982 (S) An internal routine called realloc() on something that had never been
1983 malloc()ed in the first place. Mandatory, but can be disabled by
1984 setting environment variable C<PERL_BADFREE> to 1.
1986 =item Bareword found in conditional
1988 (W) The compiler found a bareword where it expected a conditional,
1989 which often indicates that an || or && was parsed as part of the
1990 last argument of the previous construct, for example:
1994 It may also indicate a misspelled constant that has been interpreted
1997 use constant TYPO => 1;
1998 if (TYOP) { print "foo" }
2000 The C<strict> pragma is useful in avoiding such errors.
2002 =item Binary number > 0b11111111111111111111111111111111 non-portable
2004 (W) The binary number you specified is larger than 2**32-1
2005 (4294967295) and therefore non-portable between systems. See
2006 L<perlport> for more on portability concerns.
2008 =item Bit vector size > 32 non-portable
2010 (W) Using bit vector sizes larger than 32 is non-portable.
2012 =item Buffer overflow in prime_env_iter: %s
2014 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2015 %ENV, it encountered a logical name or symbol definition which was too long,
2016 so it was truncated to the string shown.
2018 =item Can't check filesystem of script "%s"
2020 (P) For some reason you can't check the filesystem of the script for nosuid.
2022 =item Can't declare class for non-scalar %s in "%s"
2024 (S) Currently, only scalar variables can declared with a specific class
2025 qualifier in a "my" or "our" declaration. The semantics may be extended
2026 for other types of variables in future.
2028 =item Can't declare %s in "%s"
2030 (F) Only scalar, array, and hash variables may be declared as "my" or
2031 "our" variables. They must have ordinary identifiers as names.
2033 =item Can't ignore signal CHLD, forcing to default
2035 (W) Perl has detected that it is being run with the SIGCHLD signal
2036 (sometimes known as SIGCLD) disabled. Since disabling this signal
2037 will interfere with proper determination of exit status of child
2038 processes, Perl has reset the signal to its default value.
2039 This situation typically indicates that the parent program under
2040 which Perl may be running (e.g. cron) is being very careless.
2042 =item Can't modify non-lvalue subroutine call
2044 (F) Subroutines meant to be used in lvalue context should be declared as
2045 such, see L<perlsub/"Lvalue subroutines">.
2047 =item Can't read CRTL environ
2049 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2050 from the CRTL's internal environment array and discovered the array was
2051 missing. You need to figure out where your CRTL misplaced its environ
2052 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2054 =item Can't remove %s: %s, skipping file
2056 (S) You requested an inplace edit without creating a backup file. Perl
2057 was unable to remove the original file to replace it with the modified
2058 file. The file was left unmodified.
2060 =item Can't return %s from lvalue subroutine
2062 (F) Perl detected an attempt to return illegal lvalues (such
2063 as temporary or readonly values) from a subroutine used as an lvalue.
2064 This is not allowed.
2066 =item Can't weaken a nonreference
2068 (F) You attempted to weaken something that was not a reference. Only
2069 references can be weakened.
2071 =item Character class [:%s:] unknown
2073 (F) The class in the character class [: :] syntax is unknown.
2076 =item Character class syntax [%s] belongs inside character classes
2078 (W) The character class constructs [: :], [= =], and [. .] go
2079 I<inside> character classes, the [] are part of the construct,
2080 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2081 are not currently implemented; they are simply placeholders for
2084 =item Constant is not %s reference
2086 (F) A constant value (perhaps declared using the C<use constant> pragma)
2087 is being dereferenced, but it amounts to the wrong type of reference. The
2088 message indicates the type of reference that was expected. This usually
2089 indicates a syntax error in dereferencing the constant value.
2090 See L<perlsub/"Constant Functions"> and L<constant>.
2092 =item constant(%s): %%^H is not localized
2094 (F) When setting compile-time-lexicalized hash %^H one should set the
2095 corresponding bit of $^H as well.
2097 =item constant(%s): %s
2099 (F) Compile-time-substitutions (such as overloaded constants and
2100 character names) were not correctly set up.
2102 =item defined(@array) is deprecated
2104 (D) defined() is not usually useful on arrays because it checks for an
2105 undefined I<scalar> value. If you want to see if the array is empty,
2106 just use C<if (@array) { # not empty }> for example.
2108 =item defined(%hash) is deprecated
2110 (D) defined() is not usually useful on hashes because it checks for an
2111 undefined I<scalar> value. If you want to see if the hash is empty,
2112 just use C<if (%hash) { # not empty }> for example.
2114 =item Did not produce a valid header
2118 =item Did you mean "local" instead of "our"?
2120 (W) Remember that "our" does not localize the declared global variable.
2121 You have declared it again in the same lexical scope, which seems superfluous.
2123 =item Document contains no data
2127 =item entering effective %s failed
2129 (F) While under the C<use filetest> pragma, switching the real and
2130 effective uids or gids failed.
2132 =item false [] range "%s" in regexp
2134 (W) A character class range must start and end at a literal character, not
2135 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2136 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2139 =item Filehandle %s opened only for output
2141 (W) You tried to read from a filehandle opened only for writing. If you
2142 intended it to be a read/write filehandle, you needed to open it with
2143 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2144 you intended only to read from the file, use "E<lt>". See
2147 =item flock() on closed filehandle %s
2149 (W) The filehandle you're attempting to flock() got itself closed some
2150 time before now. Check your logic flow. flock() operates on filehandles.
2151 Are you attempting to call flock() on a dirhandle by the same name?
2153 =item Global symbol "%s" requires explicit package name
2155 (F) You've said "use strict vars", which indicates that all variables
2156 must either be lexically scoped (using "my"), declared beforehand using
2157 "our", or explicitly qualified to say which package the global variable
2160 =item Hexadecimal number > 0xffffffff non-portable
2162 (W) The hexadecimal number you specified is larger than 2**32-1
2163 (4294967295) and therefore non-portable between systems. See
2164 L<perlport> for more on portability concerns.
2166 =item Ill-formed CRTL environ value "%s"
2168 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2169 environ array, and encountered an element without the C<=> delimiter
2170 used to spearate keys from values. The element is ignored.
2172 =item Ill-formed message in prime_env_iter: |%s|
2174 (W) A warning peculiar to VMS. Perl tried to read a logical name
2175 or CLI symbol definition when preparing to iterate over %ENV, and
2176 didn't see the expected delimiter between key and value, so the
2179 =item Illegal binary digit %s
2181 (F) You used a digit other than 0 or 1 in a binary number.
2183 =item Illegal binary digit %s ignored
2185 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2186 Interpretation of the binary number stopped before the offending digit.
2188 =item Illegal number of bits in vec
2190 (F) The number of bits in vec() (the third argument) must be a power of
2191 two from 1 to 32 (or 64, if your platform supports that).
2193 =item Integer overflow in %s number
2195 (W) The hexadecimal, octal or binary number you have specified either
2196 as a literal or as an argument to hex() or oct() is too big for your
2197 architecture, and has been converted to a floating point number. On a
2198 32-bit architecture the largest hexadecimal, octal or binary number
2199 representable without overflow is 0xFFFFFFFF, 037777777777, or
2200 0b11111111111111111111111111111111 respectively. Note that Perl
2201 transparently promotes all numbers to a floating point representation
2202 internally--subject to loss of precision errors in subsequent
2205 =item Invalid %s attribute: %s
2207 The indicated attribute for a subroutine or variable was not recognized
2208 by Perl or by a user-supplied handler. See L<attributes>.
2210 =item Invalid %s attributes: %s
2212 The indicated attributes for a subroutine or variable were not recognized
2213 by Perl or by a user-supplied handler. See L<attributes>.
2215 =item invalid [] range "%s" in regexp
2217 The offending range is now explicitly displayed.
2219 =item Invalid separator character %s in attribute list
2221 (F) Something other than a colon or whitespace was seen between the
2222 elements of an attribute list. If the previous attribute
2223 had a parenthesised parameter list, perhaps that list was terminated
2224 too soon. See L<attributes>.
2226 =item Invalid separator character %s in subroutine attribute list
2228 (F) Something other than a colon or whitespace was seen between the
2229 elements of a subroutine attribute list. If the previous attribute
2230 had a parenthesised parameter list, perhaps that list was terminated
2233 =item leaving effective %s failed
2235 (F) While under the C<use filetest> pragma, switching the real and
2236 effective uids or gids failed.
2238 =item Lvalue subs returning %s not implemented yet
2240 (F) Due to limitations in the current implementation, array and hash
2241 values cannot be returned in subroutines used in lvalue context.
2242 See L<perlsub/"Lvalue subroutines">.
2244 =item Method %s not permitted
2248 =item Missing %sbrace%s on \N{}
2250 (F) Wrong syntax of character name literal C<\N{charname}> within
2251 double-quotish context.
2253 =item Missing command in piped open
2255 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2256 construction, but the command was missing or blank.
2258 =item Missing name in "my sub"
2260 (F) The reserved syntax for lexically scoped subroutines requires that they
2261 have a name with which they can be found.
2263 =item No %s specified for -%c
2265 (F) The indicated command line switch needs a mandatory argument, but
2266 you haven't specified one.
2268 =item No package name allowed for variable %s in "our"
2270 (F) Fully qualified variable names are not allowed in "our" declarations,
2271 because that doesn't make much sense under existing semantics. Such
2272 syntax is reserved for future extensions.
2274 =item No space allowed after -%c
2276 (F) The argument to the indicated command line switch must follow immediately
2277 after the switch, without intervening spaces.
2279 =item no UTC offset information; assuming local time is UTC
2281 (S) A warning peculiar to VMS. Perl was unable to find the local
2282 timezone offset, so it's assuming that local system time is equivalent
2283 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2284 to translate to the number of seconds which need to be added to UTC to
2287 =item Octal number > 037777777777 non-portable
2289 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2290 and therefore non-portable between systems. See L<perlport> for more
2291 on portability concerns.
2293 See also L<perlport> for writing portable code.
2295 =item panic: del_backref
2297 (P) Failed an internal consistency check while trying to reset a weak
2300 =item panic: kid popen errno read
2302 (F) forked child returned an incomprehensible message about its errno.
2304 =item panic: magic_killbackrefs
2306 (P) Failed an internal consistency check while trying to reset all weak
2307 references to an object.
2309 =item Parentheses missing around "%s" list
2311 (W) You said something like
2317 my ($foo, $bar) = @_;
2319 Remember that "my", "our", and "local" bind tighter than comma.
2321 =item Possible Y2K bug: %s
2323 (W) You are concatenating the number 19 with another number, which
2324 could be a potential Year 2000 problem.
2326 =item Premature end of script headers
2330 =item Repeat count in pack overflows
2332 (F) You can't specify a repeat count so large that it overflows
2333 your signed integers. See L<perlfunc/pack>.
2335 =item Repeat count in unpack overflows
2337 (F) You can't specify a repeat count so large that it overflows
2338 your signed integers. See L<perlfunc/unpack>.
2340 =item realloc() of freed memory ignored
2342 (S) An internal routine called realloc() on something that had already
2345 =item Reference is already weak
2347 (W) You have attempted to weaken a reference that is already weak.
2348 Doing so has no effect.
2350 =item setpgrp can't take arguments
2352 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2353 unlike POSIX setpgid(), which takes a process ID and process group ID.
2355 =item Strange *+?{} on zero-length expression
2357 (W) You applied a regular expression quantifier in a place where it
2358 makes no sense, such as on a zero-width assertion.
2359 Try putting the quantifier inside the assertion instead. For example,
2360 the way to match "abc" provided that it is followed by three
2361 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2363 =item switching effective %s is not implemented
2365 (F) While under the C<use filetest> pragma, we cannot switch the
2366 real and effective uids or gids.
2368 =item This Perl can't reset CRTL environ elements (%s)
2370 =item This Perl can't set CRTL environ elements (%s=%s)
2372 (W) Warnings peculiar to VMS. You tried to change or delete an element
2373 of the CRTL's internal environ array, but your copy of Perl wasn't
2374 built with a CRTL that contained the setenv() function. You'll need to
2375 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2376 L<perlvms>) so that the environ array isn't the target of the change to
2377 %ENV which produced the warning.
2379 =item Unknown open() mode '%s'
2381 (F) The second argument of 3-argument open() is not among the list
2382 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2383 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2385 =item Unknown process %x sent message to prime_env_iter: %s
2387 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2388 iterating over it, and someone else stuck a message in the stream of
2389 data Perl expected. Someone's very confused, or perhaps trying to
2390 subvert Perl's population of %ENV for nefarious purposes.
2392 =item Unrecognized escape \\%c passed through
2394 (W) You used a backslash-character combination which is not recognized
2395 by Perl. The character was understood literally.
2397 =item Unterminated attribute parameter in attribute list
2399 (F) The lexer saw an opening (left) parenthesis character while parsing an
2400 attribute list, but the matching closing (right) parenthesis
2401 character was not found. You may need to add (or remove) a backslash
2402 character to get your parentheses to balance. See L<attributes>.
2404 =item Unterminated attribute list
2406 (F) The lexer found something other than a simple identifier at the start
2407 of an attribute, and it wasn't a semicolon or the start of a
2408 block. Perhaps you terminated the parameter list of the previous attribute
2409 too soon. See L<attributes>.
2411 =item Unterminated attribute parameter in subroutine attribute list
2413 (F) The lexer saw an opening (left) parenthesis character while parsing a
2414 subroutine attribute list, but the matching closing (right) parenthesis
2415 character was not found. You may need to add (or remove) a backslash
2416 character to get your parentheses to balance.
2418 =item Unterminated subroutine attribute list
2420 (F) The lexer found something other than a simple identifier at the start
2421 of a subroutine attribute, and it wasn't a semicolon or the start of a
2422 block. Perhaps you terminated the parameter list of the previous attribute
2425 =item Value of CLI symbol "%s" too long
2427 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2428 element from a CLI symbol table, and found a resultant string longer
2429 than 1024 characters. The return value has been truncated to 1024
2432 =item Version number must be a constant number
2434 (P) The attempt to translate a C<use Module n.n LIST> statement into
2435 its equivalent C<BEGIN> block found an internal inconsistency with
2440 =head1 Obsolete Diagnostics
2444 =item Character class syntax [: :] is reserved for future extensions
2446 (W) Within regular expression character classes ([]) the syntax beginning
2447 with "[:" and ending with ":]" is reserved for future extensions.
2448 If you need to represent those character sequences inside a regular
2449 expression character class, just quote the square brackets with the
2450 backslash: "\[:" and ":\]".
2452 =item Ill-formed logical name |%s| in prime_env_iter
2454 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2455 to iterate over %ENV which violates the syntactic rules governing logical
2456 names. Because it cannot be translated normally, it is skipped, and will not
2457 appear in %ENV. This may be a benign occurrence, as some software packages
2458 might directly modify logical name tables and introduce nonstandard names,
2459 or it may indicate that a logical name table has been corrupted.
2461 =item Probable precedence problem on %s
2463 (W) The compiler found a bareword where it expected a conditional,
2464 which often indicates that an || or && was parsed as part of the
2465 last argument of the previous construct, for example:
2469 =item regexp too big
2471 (F) The current implementation of regular expressions uses shorts as
2472 address offsets within a string. Unfortunately this means that if
2473 the regular expression compiles to longer than 32767, it'll blow up.
2474 Usually when you want a regular expression this big, there is a better
2475 way to do it with multiple statements. See L<perlre>.
2477 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2479 (D) Perl versions before 5.004 misinterpreted any type marker followed
2480 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2481 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2483 However, the developers of Perl 5.004 could not fix this bug completely,
2484 because at least two widely-used modules depend on the old meaning of
2485 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2486 old (broken) way inside strings; but it generates this message as a
2487 warning. And in Perl 5.005, this special treatment will cease.
2493 If you find what you think is a bug, you might check the
2494 articles recently posted to the comp.lang.perl.misc newsgroup.
2495 There may also be information at http://www.perl.com/perl/, the Perl
2498 If you believe you have an unreported bug, please run the B<perlbug>
2499 program included with your release. Make sure to trim your bug down
2500 to a tiny but sufficient test case. Your bug report, along with the
2501 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2502 analysed by the Perl porting team.
2506 The F<Changes> file for exhaustive details on what changed.
2508 The F<INSTALL> file for how to build Perl.
2510 The F<README> file for general stuff.
2512 The F<Artistic> and F<Copying> files for copyright information.
2516 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2517 contributions from The Perl Porters.
2519 Send omissions or corrections to <F<perlbug@perl.com>>.