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 developers
8 only. The included sources may not even build correctly on some platforms.
9 Subscribing to perl5-porters is the best way to monitor and contribute
10 to the progress of development releases (see www.perl.org for info).
12 This document describes differences between the 5.005 release and this one.
14 =head1 Incompatible Changes
16 =head2 Perl Source Incompatibilities
18 Beware that any new warnings that have been added or old ones
19 that have been enhanced are B<not> considered incompatible changes.
21 Since all new warnings must be explicitly requested via the C<-w>
22 switch or the C<warnings> pragma, it is ultimately the programmer's
23 responsibility to ensure that warnings are enabled judiciously.
27 =item CHECK is a new keyword
29 In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
30 subroutines named C<CHECK> are now special. These are queued up during
31 compilation and behave similar to END blocks, except they are called at
32 the end of compilation rather than at the end of execution. They cannot
35 =item Treatment of list slices of undef has changed
37 When taking a slice of a literal list (as opposed to a slice of
38 an array or hash), Perl used to return an empty list if the
39 result happened to be composed of all undef values.
41 The new behavior is to produce an empty list if (and only if)
42 the original list was empty. Consider the following example:
44 @a = (1,undef,undef,2)[2,1,2];
46 The old behavior would have resulted in @a having no elements.
47 The new behavior ensures it has three undefined elements.
49 Note in particular that the behavior of slices of the following
50 cases remains unchanged:
54 @a = (anything_returning_empty_list())[2,1,2];
60 =item Possibly changed pseudo-random number generator
62 In 5.005_0x and earlier, perl's rand() function used the C library
63 rand(3) function. As of 5.005_52, Configure tests for drand48(),
64 random(), and rand() (in that order) and picks the first one it finds.
65 Perl programs that depend on reproducing a specific set of pseudo-random
66 numbers will now likely produce different output. You can use
67 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
69 =item Hashing function for hash keys has changed
71 Perl hashes are not order preserving. The apparently random order
72 encountered when iterating on the contents of a hash is determined
73 by the hashing algorithm used. To improve the distribution of lower
74 bits in the hashed value, the algorithm has changed slightly as of
75 5.005_52. When iterating over hashes, this may yield a random order
76 that is B<different> from that of previous versions.
78 =item C<undef> fails on read only values
80 Using the C<undef> operator on a readonly value (such as $1) has
81 the same effect as assigning C<undef> to the readonly value--it
84 =item Close-on-exec bit may be set on pipe and socket handles
86 On systems that support a close-on-exec flag on filehandles, the
87 flag will be set for any handles created by pipe(), socketpair(),
88 socket(), and accept(), if that is warranted by the value of $^F
89 that may be in effect. Earlier versions neglected to set the flag
90 for handles created with these operators. See L<perlfunc/pipe>,
91 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
94 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
96 Perl 5.004 deprecated the interpretation of C<$$1> and
97 similar within interpolated strings to mean C<$$ . "1">,
100 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
102 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
104 delete(), each(), values() and hashes in a list context return the actual
105 values in the hash, instead of copies (as they used to in earlier
106 versions). Typical idioms for using these constructs copy the
107 returned values, but this can make a significant difference when
108 creating references to the returned values.
110 Keys in the hash are still returned as copies when iterating on
113 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
115 vec() generates a run-time error if the BITS argument is not
116 a valid power-of-two integer.
118 =item Text of some diagnostic output has changed
120 Most references to internal Perl operations in diagnostics
121 have been changed to be more descriptive. This may be an
122 issue for programs that may incorrectly rely on the exact
123 text of diagnostics for proper functioning.
125 =item C<%@> has been removed
127 The undocumented special variable C<%@> that used to accumulate
128 "background" errors (such as those that happen in DESTROY())
129 has been removed, because it could potentially result in memory
132 =item Parenthesized not() behaves like a list operator
134 The C<not> operator now falls under the "if it looks like a function,
135 it behaves like a function" rule.
137 As a result, the parenthesized form can be used with C<grep> and C<map>.
138 The following construct used to be a syntax error before, but it works
141 grep not($_), @things;
143 On the other hand, using C<not> with a literal list slice may not
144 work. The following previously allowed construct:
146 print not (1,2,3)[0];
148 needs to be written with additional parentheses now:
150 print not((1,2,3)[0]);
152 The behavior remains unaffected when C<not> is not followed by parentheses.
154 =item Semantics of bareword prototype C<(*)> have changed
156 Arguments prototyped as C<*> will now be visible within the subroutine
157 as either a simple scalar or as a reference to a typeglob. Perl 5.005
158 always coerced simple scalar arguments to a typeglob, which wasn't useful
159 in situations where the subroutine must distinguish between a simple
160 scalar and a typeglob. See L<perlsub/Prototypes>.
164 =head2 C Source Incompatibilities
168 =item C<PERL_POLLUTE>
170 Release 5.005 grandfathered old global symbol names by providing preprocessor
171 macros for extension source compatibility. As of release 5.6, these
172 preprocessor definitions are not available by default. You need to explicitly
173 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
174 extensions still using the old symbols, this option can be
175 specified via MakeMaker:
177 perl Makefile.PL POLLUTE=1
179 =item C<PERL_IMPLICIT_CONTEXT>
181 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
182 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
183 intended to be enabled by users at this time.
185 This new build option provides a set of macros for all API functions
186 such that an implicit interpreter/thread context argument is passed to
187 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
188 amounts to a macro invocation that actually translates to something like
189 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
190 to not have any significant source compatibility issues, the difference
191 between a macro and a real function call will need to be considered.
193 This means that there B<is> a source compatibility issue as a result of
194 this if your extensions attempt to use pointers to any of the Perl API
197 Note that the above issue is not relevant to the default build of
198 Perl, whose interfaces continue to match those of prior versions
199 (but subject to the other options described here).
201 See L<perlguts/"The Perl API"> for detailed information on the
202 ramifications of building Perl using this option.
204 =item C<PERL_POLLUTE_MALLOC>
206 Enabling Perl's malloc in release 5.005 and earlier caused
207 the namespace of system versions of the malloc family of functions to
208 be usurped by the Perl versions, since by default they used the
211 Besides causing problems on platforms that do not allow these functions to
212 be cleanly replaced, this also meant that the system versions could not
213 be called in programs that used Perl's malloc. Previous versions of Perl
214 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
215 EMBEDMYMALLOC preprocessor definitions.
217 As of release 5.6, Perl's malloc family of functions have default names
218 distinct from the system versions. You need to explicitly compile perl with
219 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
220 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
223 Note that these functions do B<not> constitute Perl's memory allocation API.
224 See L<perlguts/"Memory Allocation"> for further information about that.
228 =head2 Compatible C Source API Changes
232 =item C<PATCHLEVEL> is now C<PERL_VERSION>
234 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
235 are now available by default from perl.h, and reflect the base revision,
236 patchlevel, and subversion respectively. C<PERL_REVISION> had no
237 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
238 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
240 The new names cause less pollution of the B<cpp> namespace and reflect what
241 the numbers have come to stand for in common practice. For compatibility,
242 the old names are still supported when F<patchlevel.h> is explicitly
243 included (as required before), so there is no source incompatibility
246 =item Support for C++ exceptions
248 change#3386, also needs perlguts documentation
249 [TODO - Chip Salzenberg <chip@perlsupport.com>]
253 =head2 Binary Incompatibilities
255 In general, the default build of this release is expected to be binary
256 compatible for extensions built with the 5.005 release or its maintenance
257 versions. However, specific platforms may have broken binary compatibility
258 due to changes in the defaults used in hints files. Therefore, please be
259 sure to always check the platform-specific README files for any notes to
262 The usethreads or usemultiplicity builds are B<not> binary compatible
263 with the corresponding builds in 5.005.
265 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
266 among others), purely internal symbols such as parser functions and the
267 run time opcodes are not exported by default. Perl 5.005 used to export
268 all functions irrespective of whether they were considered part of the
271 For the full list of public API functions, see L<perlapi>.
273 =head1 Installation and Configuration Improvements
275 =head2 -Dusethreads means something different
277 WARNING: Support for threads continues to be an experimental feature.
278 Interfaces and implementation are subject to sudden and drastic changes.
280 The -Dusethreads flag now enables the experimental interpreter-based thread
281 support by default. To get the flavor of experimental threads that was in
282 5.005 instead, you need to ask for -Duse5005threads.
284 As of v5.5.640, interpreter-threads support is still lacking a way to
285 create new threads from Perl (i.e., C<use Thread;> will not work with
286 interpreter threads). C<use Thread;> continues to be available when you
287 ask for -Duse5005threads, bugs and all.
289 =head2 Perl's version numbering has changed
291 Beginning with Perl version 5.6, the version number convention has been
292 changed to a "dotted tuple" scheme that is more commonly found in open
295 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
296 The next development series following v5.6 will be numbered v5.7.x,
297 beginning with v5.7.0, and the next major production release following
300 The v1.2.3 syntax is also now legal in Perl. See L<Support for version tuples>
303 To cope with the new versioning system's use of at least three significant
304 digits for each version component, the method used for incrementing the
305 subversion number has also changed slightly. We assume that versions older
306 than v5.6 have been incrementing the subversion component in multiples of
307 10. Versions after v5.6 will increment them by 1. Thus, using the new
308 notation, 5.005_03 is the same as v5.5.30, and the first maintenance
309 version following v5.6 will be v5.6.1, which amounts to a floating point
312 =head2 New Configure flags
314 The following new flags may be enabled on the Configure command line
315 by running Configure with C<-Dflag>.
324 =head2 -Dusethreads and -Duse64bits now more daring
326 The Configure options enabling the use of threads and the use of
327 64-bitness are now more daring in the sense that they no more have an
328 explicit list of operating systems of known threads/64-bit
329 capabilities. In other words: if your operating system has the
330 necessary APIs and datatypes, you should be able just to go ahead and
331 use them, for threads by Configure -Dusethreads, and for 64 bits
332 either explicitly by Configure -Duse64bits or implicitly if your
333 system has 64 bit wide datatypes. See also L<"64-bit support">.
337 Some platforms have "long doubles", floating point numbers of even
338 larger range than ordinary "doubles". To enable using long doubles for
339 Perl's scalars, use -Duselongdouble.
343 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
344 See also L<"64-bit support">.
346 =head2 -Duselargefiles
348 Some platforms support large files, files larger than two gigabytes.
349 See L<"Large file support"> for more information.
351 =head2 installusrbinperl
353 You can use "Configure -Uinstallusrbinperl" which causes installperl
354 to skip installing perl also as /usr/bin/perl. This is useful if you
355 prefer not to modify /usr/bin for some reason or another but harmful
356 because many scripts assume to find Perl in /usr/bin/perl.
360 You can use "Configure -Dusesocks" which causes Perl to probe
361 for the SOCKS (v5, not v4) proxy protocol library,
362 http://www.socks.nec.com/
366 You can "post-edit" the Configure variables using the Configure C<-A>
367 flag. The editing happens immediately after the platform specific
368 hints files have been processed but before the actual configuration
369 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
371 =head2 Enhanced Installation Directories
373 The installation structure has been enriched to improve the support for
374 maintaining multiple versions of perl, to provide locations for
375 vendor-supplied modules and scripts, and to ease maintenance of
376 locally-added modules and scripts. See the section on Installation
377 Directories in the INSTALL file for complete details. For most users
378 building and installing from source, the defaults should be fine.
382 =head2 Unicode and UTF-8 support
384 Perl can optionally use UTF-8 as its internal representation for character
385 strings. The C<utf8> and C<bytes> pragmas are used to control this support
386 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
389 =head2 Interpreter cloning, threads, and concurrency
391 WARNING: This is an experimental feature in a pre-alpha state. Use
394 Perl 5.005_63 introduces the beginnings of support for running multiple
395 interpreters concurrently in different threads. In conjunction with
396 the perl_clone() API call, which can be used to selectively duplicate
397 the state of any given interpreter, it is possible to compile a
398 piece of code once in an interpreter, clone that interpreter
399 one or more times, and run all the resulting interpreters in distinct
402 On Windows, this feature is used to emulate fork() at the interpreter
403 level. See L<perlfork>.
405 This feature is still in evolution. It is eventually meant to be used
406 to selectively clone a subroutine and data reachable from that
407 subroutine in a separate interpreter and run the cloned subroutine
408 in a separate thread. Since there is no shared data between the
409 interpreters, little or no locking will be needed (unless parts of
410 the symbol table are explicitly shared). This is obviously intended
411 to be an easy-to-use replacement for the existing threads support.
413 Support for cloning interpreters and interpreter concurrency can be
414 enabled using the -Dusethreads Configure option (see win32/Makefile for
415 how to enable it on Windows.) The resulting perl executable will be
416 functionally identical to one that was built with -Dmultiplicity, but
417 the perl_clone() API call will only be available in the former.
419 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
420 Perl source code changes that provide a clear separation between the op tree
421 and the data it operates with. The former is considered immutable, and can
422 therefore be shared between an interpreter and all of its clones, while the
423 latter is considered local to each interpreter, and is therefore copied for
426 Note that building Perl with the -Dusemultiplicity Configure option
427 is adequate if you wish to run multiple B<independent> interpreters
428 concurrently in different threads. -Dusethreads only provides the
429 additional functionality of the perl_clone() API call and other
430 support for running B<cloned> interpreters concurrently.
432 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
435 =head2 Lexically scoped warning categories
437 You can now control the granularity of warnings emitted by perl at a finer
438 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
441 =head2 Lvalue subroutines
443 WARNING: This is an experimental feature.
446 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
447 Tuomas Lukka <lukka@iki.fi>)]
449 =head2 "our" declarations
451 An "our" declaration introduces a value that can be best understood
452 as a lexically scoped symbolic alias to a global variable in the
453 package that was current where the variable was declared. This is
454 mostly useful as an alternative to the C<vars> pragma, but also provides
455 the opportunity to introduce typing and other attributes for such
456 variables. See L<perlfunc/our>.
458 =head2 Support for version tuples
460 Literals of the form v1.2.3.4 are now parsed as the utf8 string
461 C<"\x{1}\x{2}\x{3}\x{4}">. This allows comparing version numbers using
462 regular string comparison operators C<eq>, C<ne>, C<lt>, C<gt> etc.
464 These "dotted tuples" are dual-valued. They are both strings of utf8
465 characters, and floating point numbers. Thus v1.2.3.4 has the string
466 value C<"\x{1}\x{2}\x{3}\x{4}"> and the numeric value 1.002_003_004.
467 As another example, v5.5.640 has the string value C<"\x{5}\x{5}\x{280}">
468 (remember 280 hexadecimal is 640 decimal) and the numeric value
471 In conjunction with the new C<$^V> magic variable (which contains
472 the perl version in this format), such literals can be used to
473 check if you're running a particular version of Perl.
475 if ($^V and $^V gt v5.5.640) {
476 # new style version numbers are supported
479 C<require> and C<use> also support such literals:
481 require v5.6.0; # croak if $^V lt v5.6.0
482 use v5.6.0; # same, but croaks at compile-time
484 C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
485 to print ordinals of characters in arbitrary strings:
487 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
488 printf "%*vX", ":", $addr; # formats IPv6 address
489 printf "%*vb", "", $bits; # displays bitstring as contiguous 0's and 1's
491 =head2 Weak references
493 WARNING: This is an experimental feature.
495 In previous versions of Perl, you couldn't cache objects so as
496 to allow them to be deleted if the last reference from outside
497 the cache is deleted. The reference in the cache would hold a
498 reference count on the object and the objects would never be
501 Another familiar problem is with circular references. When an
502 object references itself, its reference count would never go
503 down to zero, and it would not get destroyed until the program
506 Weak references solve this by allowing you to "weaken" any
507 reference, that is, make it not count towards the reference count.
508 When the last non-weak reference to an object is deleted, the object
509 is destroyed and all the weak references to the object are
510 automatically undef-ed.
512 To use this feature, you need the WeakRef package from CPAN, which
513 contains additional documentation.
515 change#3385, also need perlguts documentation
516 [TODO - Tuomas Lukka <lukka@iki.fi>]
518 =head2 File globbing implemented internally
520 WARNING: This is currently an experimental feature. Interfaces and
521 implementation are likely to change.
523 Perl now uses the File::Glob implementation of the glob() operator
524 automatically. This avoids using an external csh process and the
525 problems associated with it.
527 =head2 Binary numbers supported
529 Binary numbers are now supported as literals, in s?printf formats, and
533 printf "The answer is: %b\n", oct("0b101010");
535 =head2 Some arrows may be omitted in calls through references
537 Perl now allows the arrow to be omitted in many constructs
538 involving subroutine calls through references. For example,
539 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
540 This is rather similar to how the arrow may be omitted from
541 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
542 required for C<foo(10)-E<gt>('bar')>.
544 =head2 exists() is supported on subroutine names
546 The exists() builtin now works on subroutine names. A subroutine
547 is considered to exist if it has been declared (even if implicitly).
548 See L<perlfunc/exists> for examples.
550 =head2 exists() and delete() are supported on array elements
552 The exists() and delete() builtins now work on simple arrays as well.
553 The behavior is similar to that on hash elements.
555 exists() can be used to check whether an array element has been
556 initialized. This avoids autovivifying array elements that don't exist.
557 If the array is tied, the EXISTS() method in the corresponding tied
558 package will be invoked.
560 delete() may be used to remove an element from the array and return
561 it. The array element at that position returns to its unintialized
562 state, so that testing for the same element with exists() will return
563 false. If the element happens to be the one at the end, the size of
564 the array also shrinks up to the highest element that tests true for
565 exists(), or 0 if none such is found. If the array is tied, the DELETE()
566 method in the corresponding tied package will be invoked.
568 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
570 =head2 syswrite() ease-of-use
572 The length argument of C<syswrite()> has become optional.
574 =head2 File and directory handles can be autovivified
576 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
577 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
578 socket(), and accept()) now autovivify a file or directory handle
579 if the handle passed to them is an uninitialized scalar variable. This
580 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
581 to be used to create filehandles that will conveniently be closed
582 automatically when the scope ends, provided there are no other references
583 to them. This largely eliminates the need for typeglobs when opening
584 filehandles that must be passed around, as in the following example:
588 or die "Can't open '@_': $!";
593 my $f = myopen("</etc/motd");
595 # $f implicitly closed here
598 [TODO - this idiom needs more pod penetration]
600 =head2 64-bit support
602 All platforms that have 64-bit integers either (a) natively as longs
603 or ints (b) via special compiler flags (c) using long long are able to
604 use "quads" (64-integers) as follows:
610 constants (decimal, hexadecimal, octal, binary) in the code
614 arguments to oct() and hex()
618 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
626 pack() and unpack() "q" and "Q" formats
630 in basic arithmetics: + - * / %
634 vec() (but see the below note about bit arithmetics)
638 Note that unless you have the case (a) you will have to configure
639 and compile Perl using the -Duse64bits Configure flag.
641 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
642 64-bit clean, they are explictly forced to be 32-bit because of
643 tangled backward compatibility issues. This limitation is subject to
644 change. Bit arithmetics for bit vector scalars (created by vec()) are
645 not limited in their width.
647 Last but not least: note that due to Perl's habit of always using
648 floating point numbers the quads are still not true integers.
649 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
650 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
651 are silently promoted to floating point numbers, after which they will
652 start losing precision (their lower digits).
654 =head2 Large file support
656 If you have filesystems that support "large files" (files larger than
657 2 gigabytes), you may now also be able to create and access them from
658 Perl. You have to use Configure -Duselargefiles. Turning on the
659 large file support turns on also the 64-bit support on many platforms.
660 Beware that unless your filesystem also supports "sparse files" seeking
661 to umpteen petabytes may be unadvisable.
663 Note that in addition to requiring a proper file system to do large
664 files you may also need to adjust your per-process (or your
665 per-system, or per-process-group, or per-user-group) maximum filesize
666 limits before running Perl scripts that try to handle large files,
667 especially if you intend to write such files.
669 Finally, in addition to your process/process group maximum filesize
670 limits, you may have quota limits on your filesystems that stop you
671 (your user id or your user group id) from using large files.
673 Adjusting your process/user/group/file system/operating system limits
674 is outside the scope of Perl core language. For process limits, you
675 may try increasing the limits using your shell's limits/limit/ulimit
676 command before running Perl. The BSD::Resource extension (not
677 included with the standard Perl distribution) may also be of use, it
678 offers the getrlimit/setrlimit interface that can be used to adjust
679 process resource usage limits, including the maximum filesize limit.
683 In some systems you may be able to use long doubles to enhance the
684 range and precision of your double precision floating point numbers
685 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
686 this support (if it is available).
690 You can "Configure -Dusemorebits" to turn on both the 64-bit support
691 and the long double support.
693 =head2 Enhanced support for sort() subroutines
695 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
696 now be used as sort subroutines. In either case, the two elements to
697 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
699 For unprototyped sort subroutines, the historical behavior of passing
700 the elements to be compared as the global variables $a and $b remains
703 =head2 Better syntax checks on parenthesized unary operators
707 print defined(&foo,&bar,&baz);
708 print uc("foo","bar","baz");
711 used to be accidentally allowed in earlier versions, and produced
712 unpredictable behaviour. Some produced ancillary warnings
713 when used in this way; others silently did the wrong thing.
715 The parenthesized forms of most unary operators that expect a single
716 argument now ensure that they are not called with more than one
717 argument, making the cases shown above syntax errors. The usual
720 print defined &foo, &bar, &baz;
721 print uc "foo", "bar", "baz";
724 remains unchanged. See L<perlop>.
726 =head2 POSIX character class syntax [: :] supported
728 For example to match alphabetic characters use /[[:alpha:]]/.
729 See L<perlre> for details.
731 =head2 Improved C<qw//> operator
733 The C<qw//> operator is now evaluated at compile time into a true list
734 instead of being replaced with a run time call to C<split()>. This
735 removes the confusing misbehaviour of C<qw//> in scalar context, which
736 had inherited that behaviour from split().
740 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
742 now correctly prints "3|a", instead of "2|a".
744 =head2 pack() format 'Z' supported
746 The new format type 'Z' is useful for packing and unpacking null-terminated
747 strings. See L<perlfunc/"pack">.
749 =head2 pack() format modifier '!' supported
751 The new format type modifier '!' is useful for packing and unpacking
752 native shorts, ints, and longs. See L<perlfunc/"pack">.
754 =head2 pack() and unpack() support counted strings
756 The template character '/' can be used to specify a counted string
757 type to be packed or unpacked. See L<perlfunc/"pack">.
759 =head2 Comments in pack() templates
761 The '#' character in a template introduces a comment up to
762 end of the line. This facilitates documentation of pack()
765 =head2 $^X variables may now have names longer than one character
767 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
768 error. Now variable names that begin with a control character may be
769 arbitrarily long. However, for compatibility reasons, these variables
770 I<must> be written with explicit braces, as C<${^XY}> for example.
771 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
772 than one control character, such as C<${^XY^Z}>, are illegal.
774 The old syntax has not changed. As before, `^X' may be either a
775 literal control-X character or the two-character sequence `caret' plus
776 `X'. When braces are omitted, the variable name stops after the
777 control character. Thus C<"$^XYZ"> continues to be synonymous with
778 C<$^X . "YZ"> as before.
780 As before, lexical variables may not have names beginning with control
781 characters. As before, variables whose names begin with a control
782 character are always forced to be in package `main'. All such variables
783 are reserved for future extensions, except those that begin with
784 C<^_>, which may be used by user programs and are guaranteed not to
785 acquire special meaning in any future version of Perl.
787 =head2 C<use attrs> implicit in subroutine attributes
789 Formerly, if you wanted to mark a subroutine as being a method call or
790 as requiring an automatic lock() when it is entered, you had to declare
791 that with a C<use attrs> pragma in the body of the subroutine.
792 That can now be accomplished with declaration syntax, like this:
794 sub mymethod : locked method ;
796 sub mymethod : locked method {
800 sub othermethod :locked :method ;
802 sub othermethod :locked :method {
807 (Note how only the first C<:> is mandatory, and whitespace surrounding
808 the C<:> is optional.)
810 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
811 with the stubs they provide. See L<attributes>.
813 =head2 Regular expression improvements
815 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
816 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
818 =head2 Overloading improvements
821 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
823 =head2 open() with more than two arguments
825 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
827 =head2 Support for interpolating named characters
830 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
832 =head2 Experimental support for user-hooks in @INC
834 [TODO - Ken Fox <kfox@ford.com>]
836 =head2 C<require> and C<do> may be overridden
838 C<require> and C<do 'file'> operations may be overridden locally
839 by importing subroutines of the same name into the current package
840 (or globally by importing them into the CORE::GLOBAL:: namespace).
841 Overriding C<require> will also affect C<use>, provided the override
842 is visible at compile-time.
843 See L<perlsub/"Overriding Built-in Functions">.
845 =head2 New variable $^C reflects C<-c> switch
847 C<$^C> has a boolean value that reflects whether perl is being run
848 in compile-only mode (i.e. via the C<-c> switch). Since
849 BEGIN blocks are executed under such conditions, this variable
850 enables perl code to determine whether actions that make sense
851 only during normal running are warranted. See L<perlvar>.
853 =head2 New variable $^V contains Perl version in v5.6.0 format
855 C<$^V> contains the Perl version number as a version tuple that
856 can be used in string or numeric comparisons. See
857 C<Support for version tuples> for an example.
859 =head2 Optional Y2K warnings
861 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
862 it emits optional warnings when concatenating the number 19
865 This behavior must be specifically enabled when running Configure.
866 See F<INSTALL> and F<README.Y2K>.
868 =head1 Significant bug fixes
870 =head2 E<lt>HANDLEE<gt> on empty files
872 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
873 zero length (instead of C<undef>, as it used to) the first time the
874 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
877 This means that the following will append "foo" to an empty file (it used
880 perl -0777 -pi -e 's/^/foo/' empty_file
884 perl -pi -e 's/^/foo/' empty_file
886 is unchanged (it continues to leave the file empty).
888 =head2 C<eval '...'> improvements
890 Line numbers (as reflected by caller() and most diagnostics) within
891 C<eval '...'> were often incorrect when here documents were involved.
892 This has been corrected.
894 Lexical lookups for variables appearing in C<eval '...'> within
895 functions that were themselves called within an C<eval '...'> were
896 searching the wrong place for lexicals. The lexical search now
897 correctly ends at the subroutine's block boundary.
899 Parsing of here documents used to be flawed when they appeared as
900 the replacement expression in C<eval 's/.../.../e'>. This has
903 =head2 All compilation errors are true errors
905 Some "errors" encountered at compile time were by neccessity
906 generated as warnings followed by eventual termination of the
907 program. This enabled more such errors to be reported in a
908 single run, rather than causing a hard stop at the first error
909 that was encountered.
911 The mechanism for reporting such errors has been reimplemented
912 to queue compile-time errors and report them at the end of the
913 compilation as true errors rather than as warnings. This fixes
914 cases where error messages leaked through in the form of warnings
915 when code was compiled at run time using C<eval STRING>, and
916 also allows such errors to be reliably trapped using __DIE__ hooks.
918 =head2 Automatic flushing of output buffers
920 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
921 of all files opened for output when the operation
922 was attempted. This mostly eliminates confusing
923 buffering mishaps suffered by users unaware of how Perl internally
926 =head2 Better diagnostics on meaningless filehandle operations
928 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
929 are compile time errors. Attempting to read from filehandles that
930 were opened only for writing will now produce warnings (just as
931 writing to read-only filehandles does).
933 =head2 Where possible, buffered data discarded from duped input filehandle
935 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
936 was previously read and buffered in C<OLD> before duping the handle.
937 On platforms where doing this is allowed, the next read operation
938 on C<NEW> will return the same data as the corresponding operation
939 on C<OLD>. Formerly, it would have returned the data from the start
940 of the following disk block instead.
942 =head2 eof() has the same old magic as <>
944 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
945 yet been made. C<eof()> has been changed to have a little magic of its
946 own, it now opens the C<E<lt>E<gt>> files.
948 =head2 system(), backticks and pipe open now reflect exec() failure
950 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
951 etc., are implemented via fork() and exec(). When the underlying
952 exec() fails, earlier versions did not report the error properly,
953 since the exec() happened to be in a different process.
955 The child process now communicates with the parent about the
956 error in launching the external command, which allows these
957 constructs to return with their usual error value and set $!.
959 =head2 Implicitly closed filehandles are safer
961 Sometimes implicitly closed filehandles (as when they are localized,
962 and Perl automatically closes them on exiting the scope) could
963 inadvertently set $? or $!. This has been corrected.
965 =head2 C<(\$)> prototype and C<$foo{a}>
967 An scalar reference prototype now correctly allows a hash or
968 array element in that slot.
970 =head2 Pseudo-hashes work better
972 Dereferencing some types of reference values in a pseudo-hash,
973 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
976 When applied to a pseudo-hash element, exists() now reports whether
977 the specified value exists, not merely if the key is valid.
979 delete() now works on pseudo-hashes. When given a pseudo-hash element
980 or slice it deletes the values corresponding to the keys (but not the keys
981 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
983 =head2 C<goto &sub> and AUTOLOAD
985 The C<goto &sub> construct works correctly when C<&sub> happens
988 =head2 C<-bareword> allowed under C<use integer>
990 The autoquoting of barewords preceded by C<-> did not work
991 in prior versions when the C<integer> pragma was enabled.
994 =head2 Boolean assignment operators are legal lvalues
996 Constructs such as C<($a ||= 2) += 1> are now allowed.
998 =head2 C<sort $coderef @foo> allowed
1000 sort() did not accept a subroutine reference as the comparison
1001 function in earlier versions. This is now permitted.
1003 =head2 Failures in DESTROY()
1005 When code in a destructor threw an exception, it went unnoticed
1006 in earlier versions of Perl, unless someone happened to be
1007 looking in $@ just after the point the destructor happened to
1008 run. Such failures are now visible as warnings when warnings are
1011 =head2 Locale bugs fixed
1013 printf() and sprintf() previously reset the numeric locale
1014 back to the default "C" locale. This has been fixed.
1016 Numbers formatted according to the local numeric locale
1017 (such as using a decimal comma instead of a decimal dot) caused
1018 "isn't numeric" warnings, even while the operations accessing
1019 those numbers produced correct results. The warnings are gone.
1023 The C<eval 'return sub {...}'> construct could sometimes leak
1024 memory. This has been fixed.
1026 Operations that aren't filehandle constructors used to leak memory
1027 when used on invalid filehandles. This has been fixed.
1029 Constructs that modified C<@_> could fail to deallocate values
1030 in C<@_> and thus leak memory. This has been corrected.
1032 =head2 Spurious subroutine stubs after failed subroutine calls
1034 Perl could sometimes create empty subroutine stubs when a
1035 subroutine was not found in the package. Such cases stopped
1036 later method lookups from progressing into base packages.
1037 This has been corrected.
1039 =head2 Consistent numeric conversions
1042 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1044 =head2 Taint failures under C<-U>
1046 When running in unsafe mode, taint violations could sometimes
1047 cause silent failures. This has been fixed.
1049 =head2 END blocks and the C<-c> switch
1051 Prior versions used to run BEGIN B<and> END blocks when Perl was
1052 run in compile-only mode. Since this is typically not the expected
1053 behavior, END blocks are not executed anymore when the C<-c> switch
1056 See L<CHECK blocks> for how to run things when the compile phase ends.
1058 =head2 Potential to leak DATA filehandles
1060 Using the C<__DATA__> token creates an implicit filehandle to
1061 the file that contains the token. It is the program's
1062 responsibility to close it when it is done reading from it.
1064 This caveat is now better explained in the documentation.
1067 =head2 Diagnostics follow STDERR
1069 Diagnostic output now goes to whichever file the C<STDERR> handle
1070 is pointing at, instead of always going to the underlying C runtime
1071 library's C<stderr>.
1073 =head2 Other fixes for better diagnostics
1075 Line numbers are no longer suppressed (under most likely circumstances)
1076 during the global destruction phase.
1078 Diagnostics emitted from code running in threads other than the main
1079 thread are now accompanied by the thread ID.
1081 Embedded null characters in diagnostics now actually show up. They
1082 used to truncate the message in prior versions.
1084 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1085 if sort() is encountered in package foo.
1087 Unrecognized alphabetic escapes encountered when parsing quote
1088 constructs now generate a warning, since they may take on new
1089 semantics in later versions of Perl.
1091 =head1 Performance enhancements
1093 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1095 Many common sort() operations using a simple inlined block are now
1096 optimized for faster performance.
1098 =head2 Optimized assignments to lexical variables
1100 Certain operations in the RHS of assignment statements have been
1101 optimized to directly set the lexical variable on the LHS,
1102 eliminating redundant copying overheads.
1104 =head2 Method lookups optimized
1106 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1108 =head2 Faster mechanism to invoke XSUBs
1111 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1113 =head2 Perl_malloc() improvements
1116 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1118 =head2 Faster subroutine calls
1120 Minor changes in how subroutine calls are handled internally
1121 provide marginal improvements in performance.
1123 =head1 Platform specific changes
1125 =head2 Additional supported platforms
1131 VM/ESA is now supported.
1135 Siemens BS2000 is now supported under the POSIX Shell.
1139 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1144 GNU/Hurd is now supported.
1148 Rhapsody is now supported.
1152 EPOC is is now supported (on Psion 5).
1162 Perl now works with djgpp 2.02 (and 2.03 alpha).
1166 Environment variable names are not converted to uppercase any more.
1170 Wrong exit code from backticks now fixed.
1174 This port is still using its own builtin globbing.
1180 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1184 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1188 Site library searches failed to look for ".../site/5.XXX/lib"
1189 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1191 When given a pathname that consists only of a drivename, such
1192 as C<A:>, opendir() and stat() now use the current working
1193 directory for the drive rather than the drive root.
1195 The builtin XSUB functions in the Win32:: namespace are
1196 documented. See L<Win32>.
1198 $^X now contains the full path name of the running executable.
1200 A Win32::GetLongPathName() function is provided to complement
1201 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1203 POSIX::uname() is supported.
1205 system(1,...) now returns true process IDs rather than process
1206 handles. kill() accepts any real process id, rather than strictly
1207 return values from system(1,...).
1209 The C<Shell> module is supported.
1211 Rudimentary support for building under command.com in Windows 95
1214 Scripts are read in binary mode by default to allow ByteLoader (and
1215 the filter mechanism in general) to work properly. For compatibility,
1216 the DATA filehandle will be set to text mode if a carriage return is
1217 detected at the end of the line containing the __END__ or __DATA__
1218 token; if not, the DATA filehandle will be left open in binary mode.
1219 Earlier versions always opened the DATA filehandle in text mode.
1221 The glob() operator is implemented via the L<File::Glob> extension,
1222 which supports glob syntax of the C shell. This increases the flexibility
1223 of the glob() operator, but there may be compatibility issues for
1224 programs that relied on the older globbing syntax. If you want to
1225 preserve compatibility with the older syntax, you might want to put
1226 a C<use File::DosGlob;> in your program. For details and compatibility
1227 information, see L<File::Glob>.
1237 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1241 IO constants (SEEK_*, _IO*).
1245 Directory-related IO methods (new, read, close, rewind, tied delete).
1247 =item lib/io_multihomed
1249 INET sockets with multi-homed hosts.
1261 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1265 File test operators.
1269 Verify operations that access pad objects (lexicals and temporaries).
1273 Verify C<exists &sub> operations.
1277 =head1 Modules and Pragmata
1285 While used internally by Perl as a pragma, this module also
1286 provides a way to fetch subroutine and variable attributes.
1291 The Perl Compiler suite has been extensively reworked for this
1294 [TODO - Vishal Bhatia <vishal@gol.com>,
1295 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1299 The ByteLoader is a dedicated extension to generate and run
1300 Perl bytecode. See L<ByteLoader>.
1304 References can now be used.
1306 The new version also allows a leading underscore in constant names, but
1307 disallows a double leading underscore (as in "__LINE__"). Some other names
1308 are disallowed or warned against, including BEGIN, END, etc. Some names
1309 which were forced into main:: used to fail silently in some cases; now they're
1310 fatal (outside of main::) and an optional warning (inside of main::).
1311 The ability to detect whether a constant had been set with a given name has
1319 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1323 A C<Maxdepth> setting can be specified to avoid venturing
1324 too deeply into deep data structures. See L<Data::Dumper>.
1326 Dumping C<qr//> objects works correctly.
1330 C<DB> is an experimental module that exposes a clean abstraction
1331 to Perl's debugging API.
1335 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1336 See C<ext/DB_File/Changes>.
1340 Devel::DProf, a Perl source code profiler has been added. See
1341 L<Devel::DProf> and L<dprofpp>.
1345 The Dumpvalue module provides screen dumps of Perl data.
1349 Overall, Benchmark results exhibit lower average error and better timing
1352 You can now run tests for I<n> seconds instead of guessing the right
1353 number of tests to run: e.g. timethese(-5, ...) will run each
1354 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1355 means "for at least 3 CPU seconds". The output format has also
1356 changed. For example:
1358 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1360 will now output something like this:
1362 Benchmark: running a, b, each for at least 5 CPU seconds...
1363 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1364 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1366 New features: "each for at least N CPU seconds...", "wallclock secs",
1367 and the "@ operations/CPU second (n=operations)".
1369 timethese() now returns a reference to a hash of Benchmark objects containing
1370 the test results, keyed on the names of the tests.
1372 timethis() now returns the iterations field in the Benchmark result object
1375 timethese(), timethis(), and the new cmpthese() (see below) can also take
1376 a format specifier of 'none' to suppress output.
1378 A new function countit() is just like timeit() except that it takes a
1379 TIME instead of a COUNT.
1381 A new function cmpthese() prints a chart comparing the results of each test
1382 returned from a timethese() call. For each possible pair of tests, the
1383 percentage speed difference (iters/sec or seconds/iter) is shown.
1385 For other details, see L<Benchmark>.
1389 The Devel::Peek module provides access to the internal representation
1390 of Perl variables and data. It is a data debugging tool for the XS programmer.
1392 =item ExtUtils::MakeMaker
1394 change#4135, also needs docs in module pod
1395 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1399 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1400 large file (more than 4GB) access Note that the O_LARGEFILE is
1401 automatically/transparently added to sysopen() flags if large file
1402 support has been configured), Free/Net/OpenBSD locking behaviour flags
1403 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1404 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1405 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1406 The chmod()/stat() S_IF* constants and S_IS* functions are available
1407 via the C<:mode> tag.
1412 A compare_text() function has been added, which allows custom
1413 comparison functions. See L<File::Compare>.
1417 File::Find now works correctly when the wanted() function is either
1418 autoloaded or is a symbolic reference.
1420 A bug that caused File::Find to lose track of the working directory
1421 when pruning top-level directories has been fixed.
1423 File::Find now also supports several other options to control its
1424 behavior. It can follow symbolic links if the C<follow> option is
1425 specified. Enabling the C<no_chdir> option will make File::Find skip
1426 changing the current directory when walking directories. The C<untaint>
1427 flag can be useful when running with taint checks enabled.
1433 This extension implements BSD-style file globbing. By default,
1434 it will also be used for the internal implementation of the glob()
1435 operator. See L<File::Glob>.
1439 New methods have been added to the File::Spec module: devnull() returns
1440 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1441 the temp directory (normally /tmp on Unix). There are now also methods
1442 to convert between absolute and relative filenames: abs2rel() and
1443 rel2abs(). For compatibility with operating systems that specify volume
1444 names in file paths, the splitpath(), splitdir(), and catdir() methods
1447 =item File::Spec::Functions
1449 The new File::Spec::Functions modules provides a function interface
1450 to the File::Spec module. Allows shorthand
1452 $fullname = catfile($dir1, $dir2, $file);
1456 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1460 Getopt::Long licensing has changed to allow the Perl Artistic License
1461 as well as the GPL. It used to be GPL only, which got in the way of
1462 non-GPL applications that wanted to use Getopt::Long.
1464 Getopt::Long encourages the use of Pod::Usage to produce help
1465 messages. For example:
1471 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1472 pod2usage(1) if $help;
1473 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1479 sample - Using GetOpt::Long and Pod::Usage
1483 sample [options] [file ...]
1486 -help brief help message
1487 -man full documentation
1495 Print a brief help message and exits.
1499 Prints the manual page and exits.
1505 B<This program> will read the given input file(s) and do someting
1506 useful with the contents thereof.
1510 See L<Pod::Usage> for details.
1512 A bug that prevented the non-option call-back E<lt>E<gt> from being
1513 specified as the first argument has been fixed.
1515 To specify the characters E<lt> and E<gt> as option starters, use
1516 E<gt>E<lt>. Note, however, that changing option starters is strongly
1521 write() and syswrite() will now accept a single-argument
1522 form of the call, for consistency with Perl's syswrite().
1524 You can now create a TCP-based IO::Socket::INET without forcing
1525 a connect attempt. This allows you to configure its options
1526 (like making it non-blocking) and then call connect() manually.
1528 A bug that prevented the IO::Socket::protocol() accessor
1529 from ever returning the correct value has been corrected.
1533 Java Perl Lingo is now distributed with Perl. See jpl/README
1534 for more information.
1538 C<use lib> now weeds out any trailing duplicate entries.
1539 C<no lib> removes all named entries.
1543 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1544 and C<~> are now supported on bigints.
1548 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1549 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1553 A little bit of radial trigonometry (cylindrical and spherical),
1554 radial coordinate conversions, and the great circle distance were added.
1556 =item Pod::Parser, Pod::InputObjects
1558 Pod::Parser is a base class for parsing and selecting sections of
1559 pod documentation from an input stream. This module takes care of
1560 identifying pod paragraphs and commands in the input and hands off the
1561 parsed paragraphs and commands to user-defined methods which are free
1562 to interpret or translate them as they see fit.
1564 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1565 for advanced users of Pod::Parser that need more about a command besides
1568 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1569 "base parser code" recommended for use by all pod2xxx translators.
1570 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1571 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1572 underway. For any questions or comments about pod parsing and translating
1573 issues and utilities, please use the pod-people@perl.org mailing list.
1575 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1577 =item Pod::Checker, podchecker
1579 This utility checks pod files for correct syntax, according to
1580 L<perlpod>. Obvious errors are flagged as such, while warnings are
1581 printed for mistakes that can be handled gracefully. The checklist is
1582 not complete yet. See L<Pod::Checker>.
1584 =item Pod::ParseUtils, Pod::Find
1586 These modules provide a set of gizmos that are useful mainly for pod
1587 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1588 returns found pod files, along with their canonical names (like
1589 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1590 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1591 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1592 (for caching information about pod files, e.g. link nodes).
1594 =item Pod::Select, podselect
1596 Pod::Select is a subclass of Pod::Parser which provides a function
1597 named "podselect()" to filter out user-specified sections of raw pod
1598 documentation from an input stream. podselect is a script that provides
1599 access to Pod::Select from other scripts to be used as a filter.
1602 =item Pod::Usage, pod2usage
1604 Pod::Usage provides the function "pod2usage()" to print usage messages for
1605 a Perl script based on its embedded pod documentation. The pod2usage()
1606 function is generally useful to all script authors since it lets them
1607 write and maintain a single source (the pods) for documentation, thus
1608 removing the need to create and maintain redundant usage message text
1609 consisting of information already in the pods.
1611 There is also a pod2usage script which can be used from other kinds of
1612 scripts to print usage messages from pods (even for non-Perl scripts
1613 with pods embedded in comments).
1615 For details and examples, please see L<Pod::Usage>.
1617 =item Pod::Text and Pod::Man
1619 [TODO - Russ Allbery <rra@stanford.edu>]
1623 An EXISTS method has been added to this module (and sdbm_exists() has
1624 been added to the underlying sdbm library), so one can now call exists
1625 on an SDBM_File tied hash and get the correct result, rather than a
1628 A bug that may have caused data loss when more than one disk block
1629 happens to be read from the database in a single FETCH() has been
1634 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1635 no longer requires syslog.ph to exist.
1639 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1640 uname() if they exist.
1644 The timelocal() and timegm() functions used to silently return bogus
1645 results when the date fell outside the machine's integer range. They
1646 now consistently croak() if the date falls in an unsupported range.
1650 The error return value in list context has been changed for all functions
1651 that return a list of values. Previously these functions returned a list
1652 with a single element C<undef> if an error occurred. Now these functions
1653 return the empty list in these situations. This applies to the following
1659 The remaining functions are unchanged and continue to return C<undef> on
1660 error even in list context.
1662 The Win32::SetLastError(ERROR) function has been added as a complement
1663 to the Win32::GetLastError() function.
1665 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1666 pathname for FILENAME in scalar context. In list context it returns
1667 a two-element list containing the fully qualified directory name and
1668 the filename. See L<Win32>.
1672 A new feature called "DBM Filters" has been added to all the
1673 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1674 DBM Filters add four new methods to each DBM module:
1681 These can be used to filter key-value pairs before the pairs are
1682 written to the database or just after they are read from the database.
1683 See L<perldbmfilter> for further information.
1689 C<use attrs> is now obsolete, and is only provided for
1690 backward-compatibility. It's been replaced by the C<sub : attributes>
1691 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1693 C<use utf8> to enable UTF-8 and Unicode support.
1695 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1698 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1699 ...). Currently only one subpragma implemented, "use filetest
1700 'access';", that uses access(2) or equivalent to check permissions
1701 instead of using stat(2) as usual. This matters in filesystems
1702 where there are ACLs (access control lists): the stat(2) might lie,
1703 but access(2) knows better.
1705 =head1 Utility Changes
1709 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1713 C<perlcc> now supports the C and Bytecode backends. By default,
1714 it generates output from the simple C backend rather than the
1715 optimized C backend.
1717 Support for non-Unix platforms has been improved.
1722 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1724 =head1 Documentation Changes
1730 The official list of public Perl API functions.
1732 =item perlcompile.pod
1734 An introduction to using the Perl Compiler suite.
1736 =item perlfilter.pod
1738 An introduction to writing Perl source filters.
1742 Some guidelines for hacking the Perl source code.
1744 =item perlintern.pod
1746 A list of internal functions in the Perl source code.
1747 (List is currently empty.)
1749 =item perlopentut.pod
1751 A tutorial on using open() effectively.
1753 =item perlreftut.pod
1755 A tutorial that introduces the essentials of references.
1759 A tutorial on managing class data for object modules.
1761 =item perlunicode.pod
1763 An introduction to Unicode support features in Perl.
1767 =head1 New or Changed Diagnostics
1771 =item "%s" variable %s masks earlier declaration in same %s
1773 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1774 effectively eliminating all access to the previous instance. This is almost
1775 always a typographical error. Note that the earlier variable will still exist
1776 until the end of the scope or until all closure referents to it are
1779 =item "my sub" not yet implemented
1781 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1784 =item "our" variable %s redeclared
1786 (W) You seem to have already declared the same global once before in the
1787 current lexical scope.
1789 =item '!' allowed only after types %s
1791 (F) The '!' is allowed in pack() and unpack() only after certain types.
1792 See L<perlfunc/pack>.
1794 =item / cannot take a count
1796 (F) You had an unpack template indicating a counted-length string,
1797 but you have also specified an explicit size for the string.
1798 See L<perlfunc/pack>.
1800 =item / must be followed by a, A or Z
1802 (F) You had an unpack template indicating a counted-length string,
1803 which must be followed by one of the letters a, A or Z
1804 to indicate what sort of string is to be unpacked.
1805 See L<perlfunc/pack>.
1807 =item / must be followed by a*, A* or Z*
1809 (F) You had a pack template indicating a counted-length string,
1810 Currently the only things that can have their length counted are a*, A* or Z*.
1811 See L<perlfunc/pack>.
1813 =item / must follow a numeric type
1815 (F) You had an unpack template that contained a '#',
1816 but this did not follow some numeric unpack specification.
1817 See L<perlfunc/pack>.
1819 =item /%s/: Unrecognized escape \\%c passed through
1821 (W) You used a backslash-character combination which is not recognized
1822 by Perl. This combination appears in an interpolated variable or a
1823 C<'>-delimited regular expression. The character was understood literally.
1825 =item /%s/: Unrecognized escape \\%c in character class passed through
1827 (W) You used a backslash-character combination which is not recognized
1828 by Perl inside character classes. The character was understood literally.
1830 =item /%s/ should probably be written as "%s"
1832 (W) You have used a pattern where Perl expected to find a string,
1833 as in the first argument to C<join>. Perl will treat the true
1834 or false result of matching the pattern against $_ as the string,
1835 which is probably not what you had in mind.
1837 =item %s() called too early to check prototype
1839 (W) You've called a function that has a prototype before the parser saw a
1840 definition or declaration for it, and Perl could not check that the call
1841 conforms to the prototype. You need to either add an early prototype
1842 declaration for the subroutine in question, or move the subroutine
1843 definition ahead of the call to get proper prototype checking. Alternatively,
1844 if you are certain that you're calling the function correctly, you may put
1845 an ampersand before the name to avoid the warning. See L<perlsub>.
1847 =item %s argument is not a HASH or ARRAY element
1849 (F) The argument to exists() must be a hash or array element, such as:
1852 $ref->[12]->["susie"]
1854 =item %s argument is not a HASH or ARRAY element or slice
1856 (F) The argument to delete() must be either a hash or array element, such as:
1859 $ref->[12]->["susie"]
1861 or a hash or array slice, such as:
1863 @foo[$bar, $baz, $xyzzy]
1864 @{$ref->[12]}{"susie", "queue"}
1866 =item %s argument is not a subroutine name
1868 (F) The argument to exists() for C<exists &sub> must be a subroutine
1869 name, and not a subroutine call. C<exists &sub()> will generate this error.
1871 =item %s package attribute may clash with future reserved word: %s
1873 (W) A lowercase attribute name was used that had a package-specific handler.
1874 That name might have a meaning to Perl itself some day, even though it
1875 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1878 =item (in cleanup) %s
1880 (W) This prefix usually indicates that a DESTROY() method raised
1881 the indicated exception. Since destructors are usually called by
1882 the system at arbitrary points during execution, and often a vast
1883 number of times, the warning is issued only once for any number
1884 of failures that would otherwise result in the same message being
1887 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1888 could also result in this warning. See L<perlcall/G_KEEPERR>.
1890 =item <> should be quotes
1892 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1895 =item Attempt to join self
1897 (F) You tried to join a thread from within itself, which is an
1898 impossible task. You may be joining the wrong thread, or you may
1899 need to move the join() to some other thread.
1901 =item Bad evalled substitution pattern
1903 (F) You've used the /e switch to evaluate the replacement for a
1904 substitution, but perl found a syntax error in the code to evaluate,
1905 most likely an unexpected right brace '}'.
1907 =item Bad realloc() ignored
1909 (S) An internal routine called realloc() on something that had never been
1910 malloc()ed in the first place. Mandatory, but can be disabled by
1911 setting environment variable C<PERL_BADFREE> to 1.
1913 =item Bareword found in conditional
1915 (W) The compiler found a bareword where it expected a conditional,
1916 which often indicates that an || or && was parsed as part of the
1917 last argument of the previous construct, for example:
1921 It may also indicate a misspelled constant that has been interpreted
1924 use constant TYPO => 1;
1925 if (TYOP) { print "foo" }
1927 The C<strict> pragma is useful in avoiding such errors.
1929 =item Binary number > 0b11111111111111111111111111111111 non-portable
1931 (W) The binary number you specified is larger than 2**32-1
1932 (4294967295) and therefore non-portable between systems. See
1933 L<perlport> for more on portability concerns.
1935 =item Bit vector size > 32 non-portable
1937 (W) Using bit vector sizes larger than 32 is non-portable.
1939 =item Buffer overflow in prime_env_iter: %s
1941 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
1942 %ENV, it encountered a logical name or symbol definition which was too long,
1943 so it was truncated to the string shown.
1945 =item Can't check filesystem of script "%s"
1947 (P) For some reason you can't check the filesystem of the script for nosuid.
1949 =item Can't declare class for non-scalar %s in "%s"
1951 (S) Currently, only scalar variables can declared with a specific class
1952 qualifier in a "my" or "our" declaration. The semantics may be extended
1953 for other types of variables in future.
1955 =item Can't declare %s in "%s"
1957 (F) Only scalar, array, and hash variables may be declared as "my" or
1958 "our" variables. They must have ordinary identifiers as names.
1960 =item Can't ignore signal CHLD, forcing to default
1962 (W) Perl has detected that it is being run with the SIGCHLD signal
1963 (sometimes known as SIGCLD) disabled. Since disabling this signal
1964 will interfere with proper determination of exit status of child
1965 processes, Perl has reset the signal to its default value.
1966 This situation typically indicates that the parent program under
1967 which Perl may be running (e.g. cron) is being very careless.
1969 =item Can't modify non-lvalue subroutine call
1971 (F) Subroutines meant to be used in lvalue context should be declared as
1972 such, see L<perlsub/"Lvalue subroutines">.
1974 =item Can't read CRTL environ
1976 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1977 from the CRTL's internal environment array and discovered the array was
1978 missing. You need to figure out where your CRTL misplaced its environ
1979 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1981 =item Can't remove %s: %s, skipping file
1983 (S) You requested an inplace edit without creating a backup file. Perl
1984 was unable to remove the original file to replace it with the modified
1985 file. The file was left unmodified.
1987 =item Can't return %s from lvalue subroutine
1989 (F) Perl detected an attempt to return illegal lvalues (such
1990 as temporary or readonly values) from a subroutine used as an lvalue.
1991 This is not allowed.
1993 =item Can't weaken a nonreference
1995 (F) You attempted to weaken something that was not a reference. Only
1996 references can be weakened.
1998 =item Character class [:%s:] unknown
2000 (F) The class in the character class [: :] syntax is unknown.
2003 =item Character class syntax [%s] belongs inside character classes
2005 (W) The character class constructs [: :], [= =], and [. .] go
2006 I<inside> character classes, the [] are part of the construct,
2007 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2008 are not currently implemented; they are simply placeholders for
2011 =item Constant is not %s reference
2013 (F) A constant value (perhaps declared using the C<use constant> pragma)
2014 is being dereferenced, but it amounts to the wrong type of reference. The
2015 message indicates the type of reference that was expected. This usually
2016 indicates a syntax error in dereferencing the constant value.
2017 See L<perlsub/"Constant Functions"> and L<constant>.
2019 =item constant(%s): %%^H is not localized
2021 (F) When setting compile-time-lexicalized hash %^H one should set the
2022 corresponding bit of $^H as well.
2024 =item constant(%s): %s
2026 (F) Compile-time-substitutions (such as overloaded constants and
2027 character names) were not correctly set up.
2029 =item defined(@array) is deprecated
2031 (D) defined() is not usually useful on arrays because it checks for an
2032 undefined I<scalar> value. If you want to see if the array is empty,
2033 just use C<if (@array) { # not empty }> for example.
2035 =item defined(%hash) is deprecated
2037 (D) defined() is not usually useful on hashes because it checks for an
2038 undefined I<scalar> value. If you want to see if the hash is empty,
2039 just use C<if (%hash) { # not empty }> for example.
2041 =item Did not produce a valid header
2045 =item Did you mean "local" instead of "our"?
2047 (W) Remember that "our" does not localize the declared global variable.
2048 You have declared it again in the same lexical scope, which seems superfluous.
2050 =item Document contains no data
2054 =item entering effective %s failed
2056 (F) While under the C<use filetest> pragma, switching the real and
2057 effective uids or gids failed.
2059 =item false [] range "%s" in regexp
2061 (W) A character class range must start and end at a literal character, not
2062 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2063 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2066 =item Filehandle %s opened only for output
2068 (W) You tried to read from a filehandle opened only for writing. If you
2069 intended it to be a read/write filehandle, you needed to open it with
2070 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2071 you intended only to read from the file, use "E<lt>". See
2074 =item flock() on closed filehandle %s
2076 (W) The filehandle you're attempting to flock() got itself closed some
2077 time before now. Check your logic flow. flock() operates on filehandles.
2078 Are you attempting to call flock() on a dirhandle by the same name?
2080 =item Global symbol "%s" requires explicit package name
2082 (F) You've said "use strict vars", which indicates that all variables
2083 must either be lexically scoped (using "my"), declared beforehand using
2084 "our", or explicitly qualified to say which package the global variable
2087 =item Hexadecimal number > 0xffffffff non-portable
2089 (W) The hexadecimal number you specified is larger than 2**32-1
2090 (4294967295) and therefore non-portable between systems. See
2091 L<perlport> for more on portability concerns.
2093 =item Ill-formed CRTL environ value "%s"
2095 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2096 environ array, and encountered an element without the C<=> delimiter
2097 used to spearate keys from values. The element is ignored.
2099 =item Ill-formed message in prime_env_iter: |%s|
2101 (W) A warning peculiar to VMS. Perl tried to read a logical name
2102 or CLI symbol definition when preparing to iterate over %ENV, and
2103 didn't see the expected delimiter between key and value, so the
2106 =item Illegal binary digit %s
2108 (F) You used a digit other than 0 or 1 in a binary number.
2110 =item Illegal binary digit %s ignored
2112 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2113 Interpretation of the binary number stopped before the offending digit.
2115 =item Illegal number of bits in vec
2117 (F) The number of bits in vec() (the third argument) must be a power of
2118 two from 1 to 32 (or 64, if your platform supports that).
2120 =item Integer overflow in %s number
2122 (W) The hexadecimal, octal or binary number you have specified either
2123 as a literal or as an argument to hex() or oct() is too big for your
2124 architecture, and has been converted to a floating point number. On a
2125 32-bit architecture the largest hexadecimal, octal or binary number
2126 representable without overflow is 0xFFFFFFFF, 037777777777, or
2127 0b11111111111111111111111111111111 respectively. Note that Perl
2128 transparently promotes all numbers to a floating point representation
2129 internally--subject to loss of precision errors in subsequent
2132 =item Invalid %s attribute: %s
2134 The indicated attribute for a subroutine or variable was not recognized
2135 by Perl or by a user-supplied handler. See L<attributes>.
2137 =item Invalid %s attributes: %s
2139 The indicated attributes for a subroutine or variable were not recognized
2140 by Perl or by a user-supplied handler. See L<attributes>.
2142 =item invalid [] range "%s" in regexp
2144 The offending range is now explicitly displayed.
2146 =item Invalid separator character %s in attribute list
2148 (F) Something other than a colon or whitespace was seen between the
2149 elements of an attribute list. If the previous attribute
2150 had a parenthesised parameter list, perhaps that list was terminated
2151 too soon. See L<attributes>.
2153 =item Invalid separator character %s in subroutine attribute list
2155 (F) Something other than a colon or whitespace was seen between the
2156 elements of a subroutine attribute list. If the previous attribute
2157 had a parenthesised parameter list, perhaps that list was terminated
2160 =item leaving effective %s failed
2162 (F) While under the C<use filetest> pragma, switching the real and
2163 effective uids or gids failed.
2165 =item Lvalue subs returning %s not implemented yet
2167 (F) Due to limitations in the current implementation, array and hash
2168 values cannot be returned in subroutines used in lvalue context.
2169 See L<perlsub/"Lvalue subroutines">.
2171 =item Method %s not permitted
2175 =item Missing %sbrace%s on \N{}
2177 (F) Wrong syntax of character name literal C<\N{charname}> within
2178 double-quotish context.
2180 =item Missing command in piped open
2182 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2183 construction, but the command was missing or blank.
2185 =item Missing name in "my sub"
2187 (F) The reserved syntax for lexically scoped subroutines requires that they
2188 have a name with which they can be found.
2190 =item No %s specified for -%c
2192 (F) The indicated command line switch needs a mandatory argument, but
2193 you haven't specified one.
2195 =item No package name allowed for variable %s in "our"
2197 (F) Fully qualified variable names are not allowed in "our" declarations,
2198 because that doesn't make much sense under existing semantics. Such
2199 syntax is reserved for future extensions.
2201 =item No space allowed after -%c
2203 (F) The argument to the indicated command line switch must follow immediately
2204 after the switch, without intervening spaces.
2206 =item no UTC offset information; assuming local time is UTC
2208 (S) A warning peculiar to VMS. Perl was unable to find the local
2209 timezone offset, so it's assuming that local system time is equivalent
2210 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2211 to translate to the number of seconds which need to be added to UTC to
2214 =item Octal number > 037777777777 non-portable
2216 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2217 and therefore non-portable between systems. See L<perlport> for more
2218 on portability concerns.
2220 See also L<perlport> for writing portable code.
2222 =item panic: del_backref
2224 (P) Failed an internal consistency check while trying to reset a weak
2227 =item panic: kid popen errno read
2229 (F) forked child returned an incomprehensible message about its errno.
2231 =item panic: magic_killbackrefs
2233 (P) Failed an internal consistency check while trying to reset all weak
2234 references to an object.
2236 =item Parentheses missing around "%s" list
2238 (W) You said something like
2244 my ($foo, $bar) = @_;
2246 Remember that "my", "our" and "local" bind closer than comma.
2248 =item Possible Y2K bug: %s
2250 (W) You are concatenating the number 19 with another number, which
2251 could be a potential Year 2000 problem.
2253 =item Premature end of script headers
2257 =item Repeat count in pack overflows
2259 (F) You can't specify a repeat count so large that it overflows
2260 your signed integers. See L<perlfunc/pack>.
2262 =item Repeat count in unpack overflows
2264 (F) You can't specify a repeat count so large that it overflows
2265 your signed integers. See L<perlfunc/unpack>.
2267 =item realloc() of freed memory ignored
2269 (S) An internal routine called realloc() on something that had already
2272 =item Reference is already weak
2274 (W) You have attempted to weaken a reference that is already weak.
2275 Doing so has no effect.
2277 =item setpgrp can't take arguments
2279 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2280 unlike POSIX setpgid(), which takes a process ID and process group ID.
2282 =item Strange *+?{} on zero-length expression
2284 (W) You applied a regular expression quantifier in a place where it
2285 makes no sense, such as on a zero-width assertion.
2286 Try putting the quantifier inside the assertion instead. For example,
2287 the way to match "abc" provided that it is followed by three
2288 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2290 =item switching effective %s is not implemented
2292 (F) While under the C<use filetest> pragma, we cannot switch the
2293 real and effective uids or gids.
2295 =item This Perl can't reset CRTL environ elements (%s)
2297 =item This Perl can't set CRTL environ elements (%s=%s)
2299 (W) Warnings peculiar to VMS. You tried to change or delete an element
2300 of the CRTL's internal environ array, but your copy of Perl wasn't
2301 built with a CRTL that contained the setenv() function. You'll need to
2302 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2303 L<perlvms>) so that the environ array isn't the target of the change to
2304 %ENV which produced the warning.
2306 =item Unknown open() mode '%s'
2308 (F) The second argument of 3-argument open() is not among the list
2309 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2310 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2312 =item Unknown process %x sent message to prime_env_iter: %s
2314 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2315 iterating over it, and someone else stuck a message in the stream of
2316 data Perl expected. Someone's very confused, or perhaps trying to
2317 subvert Perl's population of %ENV for nefarious purposes.
2319 =item Unrecognized escape \\%c passed through
2321 (W) You used a backslash-character combination which is not recognized
2322 by Perl. The character was understood literally.
2324 =item Unterminated attribute parameter in attribute list
2326 (F) The lexer saw an opening (left) parenthesis character while parsing an
2327 attribute list, but the matching closing (right) parenthesis
2328 character was not found. You may need to add (or remove) a backslash
2329 character to get your parentheses to balance. See L<attributes>.
2331 =item Unterminated attribute list
2333 (F) The lexer found something other than a simple identifier at the start
2334 of an attribute, and it wasn't a semicolon or the start of a
2335 block. Perhaps you terminated the parameter list of the previous attribute
2336 too soon. See L<attributes>.
2338 =item Unterminated attribute parameter in subroutine attribute list
2340 (F) The lexer saw an opening (left) parenthesis character while parsing a
2341 subroutine attribute list, but the matching closing (right) parenthesis
2342 character was not found. You may need to add (or remove) a backslash
2343 character to get your parentheses to balance.
2345 =item Unterminated subroutine attribute list
2347 (F) The lexer found something other than a simple identifier at the start
2348 of a subroutine attribute, and it wasn't a semicolon or the start of a
2349 block. Perhaps you terminated the parameter list of the previous attribute
2352 =item Value of CLI symbol "%s" too long
2354 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2355 element from a CLI symbol table, and found a resultant string longer
2356 than 1024 characters. The return value has been truncated to 1024
2359 =item Version number must be a constant number
2361 (P) The attempt to translate a C<use Module n.n LIST> statement into
2362 its equivalent C<BEGIN> block found an internal inconsistency with
2367 =head1 Obsolete Diagnostics
2371 =item Character class syntax [: :] is reserved for future extensions
2373 (W) Within regular expression character classes ([]) the syntax beginning
2374 with "[:" and ending with ":]" is reserved for future extensions.
2375 If you need to represent those character sequences inside a regular
2376 expression character class, just quote the square brackets with the
2377 backslash: "\[:" and ":\]".
2379 =item Ill-formed logical name |%s| in prime_env_iter
2381 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2382 to iterate over %ENV which violates the syntactic rules governing logical
2383 names. Because it cannot be translated normally, it is skipped, and will not
2384 appear in %ENV. This may be a benign occurrence, as some software packages
2385 might directly modify logical name tables and introduce nonstandard names,
2386 or it may indicate that a logical name table has been corrupted.
2388 =item Probable precedence problem on %s
2390 (W) The compiler found a bareword where it expected a conditional,
2391 which often indicates that an || or && was parsed as part of the
2392 last argument of the previous construct, for example:
2396 =item regexp too big
2398 (F) The current implementation of regular expressions uses shorts as
2399 address offsets within a string. Unfortunately this means that if
2400 the regular expression compiles to longer than 32767, it'll blow up.
2401 Usually when you want a regular expression this big, there is a better
2402 way to do it with multiple statements. See L<perlre>.
2404 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2406 (D) Perl versions before 5.004 misinterpreted any type marker followed
2407 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2408 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2410 However, the developers of Perl 5.004 could not fix this bug completely,
2411 because at least two widely-used modules depend on the old meaning of
2412 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2413 old (broken) way inside strings; but it generates this message as a
2414 warning. And in Perl 5.005, this special treatment will cease.
2420 If you find what you think is a bug, you might check the
2421 articles recently posted to the comp.lang.perl.misc newsgroup.
2422 There may also be information at http://www.perl.com/perl/, the Perl
2425 If you believe you have an unreported bug, please run the B<perlbug>
2426 program included with your release. Make sure to trim your bug down
2427 to a tiny but sufficient test case. Your bug report, along with the
2428 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2429 analysed by the Perl porting team.
2433 The F<Changes> file for exhaustive details on what changed.
2435 The F<INSTALL> file for how to build Perl.
2437 The F<README> file for general stuff.
2439 The F<Artistic> and F<Copying> files for copyright information.
2443 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2444 contributions from The Perl Porters.
2446 Send omissions or corrections to <F<perlbug@perl.com>>.