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 =head2 Perl's version numbering has changed
62 Beginning with Perl version 5.6, the version number convention has been
63 changed to a "dotted integer" scheme that is more commonly found in open
66 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
67 The next development series following v5.6 will be numbered v5.7.x,
68 beginning with v5.7.0, and the next major production release following
71 The English module now sets $PERL_VERSION to $^V (a string value) rather
72 than C<$]> (a numeric value). (This is a potential incompatibility.
73 Send us a report via perlbug if you are affected by this.)
75 The v1.2.3 syntax is also now legal in Perl.
76 See L<Support for strings represented as a vector of ordinals> for more on that.
78 To cope with the new versioning system's use of at least three significant
79 digits for each version component, the method used for incrementing the
80 subversion number has also changed slightly. We assume that versions older
81 than v5.6 have been incrementing the subversion component in multiples of
82 10. Versions after v5.6.0 will increment them by 1. Thus, using the new
83 notation, 5.005_03 is the same as v5.5.30, and the first maintenance
84 version following v5.6.0 will be v5.6.1, which amounts to a floating point
87 =item Possibly changed pseudo-random number generator
89 In 5.005_0x and earlier, perl's rand() function used the C library
90 rand(3) function. As of 5.005_52, Configure tests for drand48(),
91 random(), and rand() (in that order) and picks the first one it finds.
92 Perl programs that depend on reproducing a specific set of pseudo-random
93 numbers will now likely produce different output. You can use
94 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
96 =item Hashing function for hash keys has changed
98 Perl hashes are not order preserving. The apparently random order
99 encountered when iterating on the contents of a hash is determined
100 by the hashing algorithm used. To improve the distribution of lower
101 bits in the hashed value, the algorithm has changed slightly as of
102 5.005_52. When iterating over hashes, this may yield a random order
103 that is B<different> from that of previous versions.
105 =item C<undef> fails on read only values
107 Using the C<undef> operator on a readonly value (such as $1) has
108 the same effect as assigning C<undef> to the readonly value--it
111 =item Close-on-exec bit may be set on pipe and socket handles
113 On systems that support a close-on-exec flag on filehandles, the
114 flag will be set for any handles created by pipe(), socketpair(),
115 socket(), and accept(), if that is warranted by the value of $^F
116 that may be in effect. Earlier versions neglected to set the flag
117 for handles created with these operators. See L<perlfunc/pipe>,
118 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
121 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
123 Perl 5.004 deprecated the interpretation of C<$$1> and
124 similar within interpolated strings to mean C<$$ . "1">,
125 but still allowed it.
127 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
129 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
131 delete(), each(), values() and hashes in a list context return the actual
132 values in the hash, instead of copies (as they used to in earlier
133 versions). Typical idioms for using these constructs copy the
134 returned values, but this can make a significant difference when
135 creating references to the returned values.
137 Keys in the hash are still returned as copies when iterating on
140 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
142 vec() generates a run-time error if the BITS argument is not
143 a valid power-of-two integer.
145 =item Text of some diagnostic output has changed
147 Most references to internal Perl operations in diagnostics
148 have been changed to be more descriptive. This may be an
149 issue for programs that may incorrectly rely on the exact
150 text of diagnostics for proper functioning.
152 =item C<%@> has been removed
154 The undocumented special variable C<%@> that used to accumulate
155 "background" errors (such as those that happen in DESTROY())
156 has been removed, because it could potentially result in memory
159 =item Parenthesized not() behaves like a list operator
161 The C<not> operator now falls under the "if it looks like a function,
162 it behaves like a function" rule.
164 As a result, the parenthesized form can be used with C<grep> and C<map>.
165 The following construct used to be a syntax error before, but it works
168 grep not($_), @things;
170 On the other hand, using C<not> with a literal list slice may not
171 work. The following previously allowed construct:
173 print not (1,2,3)[0];
175 needs to be written with additional parentheses now:
177 print not((1,2,3)[0]);
179 The behavior remains unaffected when C<not> is not followed by parentheses.
181 =item Semantics of bareword prototype C<(*)> have changed
183 Arguments prototyped as C<*> will now be visible within the subroutine
184 as either a simple scalar or as a reference to a typeglob. Perl 5.005
185 always coerced simple scalar arguments to a typeglob, which wasn't useful
186 in situations where the subroutine must distinguish between a simple
187 scalar and a typeglob. See L<perlsub/Prototypes>.
191 =head2 C Source Incompatibilities
195 =item C<PERL_POLLUTE>
197 Release 5.005 grandfathered old global symbol names by providing preprocessor
198 macros for extension source compatibility. As of release 5.6, these
199 preprocessor definitions are not available by default. You need to explicitly
200 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
201 extensions still using the old symbols, this option can be
202 specified via MakeMaker:
204 perl Makefile.PL POLLUTE=1
206 =item C<PERL_IMPLICIT_CONTEXT>
208 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
209 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
210 intended to be enabled by users at this time.
212 This new build option provides a set of macros for all API functions
213 such that an implicit interpreter/thread context argument is passed to
214 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
215 amounts to a macro invocation that actually translates to something like
216 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
217 to not have any significant source compatibility issues, the difference
218 between a macro and a real function call will need to be considered.
220 This means that there B<is> a source compatibility issue as a result of
221 this if your extensions attempt to use pointers to any of the Perl API
224 Note that the above issue is not relevant to the default build of
225 Perl, whose interfaces continue to match those of prior versions
226 (but subject to the other options described here).
228 See L<perlguts/"The Perl API"> for detailed information on the
229 ramifications of building Perl using this option.
231 =item C<PERL_POLLUTE_MALLOC>
233 Enabling Perl's malloc in release 5.005 and earlier caused
234 the namespace of system versions of the malloc family of functions to
235 be usurped by the Perl versions, since by default they used the
238 Besides causing problems on platforms that do not allow these functions to
239 be cleanly replaced, this also meant that the system versions could not
240 be called in programs that used Perl's malloc. Previous versions of Perl
241 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
242 EMBEDMYMALLOC preprocessor definitions.
244 As of release 5.6, Perl's malloc family of functions have default names
245 distinct from the system versions. You need to explicitly compile perl with
246 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
247 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
250 Note that these functions do B<not> constitute Perl's memory allocation API.
251 See L<perlguts/"Memory Allocation"> for further information about that.
255 =head2 Compatible C Source API Changes
259 =item C<PATCHLEVEL> is now C<PERL_VERSION>
261 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
262 are now available by default from perl.h, and reflect the base revision,
263 patchlevel, and subversion respectively. C<PERL_REVISION> had no
264 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
265 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
267 The new names cause less pollution of the B<cpp> namespace and reflect what
268 the numbers have come to stand for in common practice. For compatibility,
269 the old names are still supported when F<patchlevel.h> is explicitly
270 included (as required before), so there is no source incompatibility
273 =item Support for C++ exceptions
275 change#3386, also needs perlguts documentation
276 [TODO - Chip Salzenberg <chip@perlsupport.com>]
280 =head2 Binary Incompatibilities
282 In general, the default build of this release is expected to be binary
283 compatible for extensions built with the 5.005 release or its maintenance
284 versions. However, specific platforms may have broken binary compatibility
285 due to changes in the defaults used in hints files. Therefore, please be
286 sure to always check the platform-specific README files for any notes to
289 The usethreads or usemultiplicity builds are B<not> binary compatible
290 with the corresponding builds in 5.005.
292 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
293 among others), purely internal symbols such as parser functions and the
294 run time opcodes are not exported by default. Perl 5.005 used to export
295 all functions irrespective of whether they were considered part of the
298 For the full list of public API functions, see L<perlapi>.
300 =head1 Installation and Configuration Improvements
302 =head2 -Dusethreads means something different
304 WARNING: Support for threads continues to be an experimental feature.
305 Interfaces and implementation are subject to sudden and drastic changes.
307 The -Dusethreads flag now enables the experimental interpreter-based thread
308 support by default. To get the flavor of experimental threads that was in
309 5.005 instead, you need to ask for -Duse5005threads.
311 As of v5.5.640, interpreter-threads support is still lacking a way to
312 create new threads from Perl (i.e., C<use Thread;> will not work with
313 interpreter threads). C<use Thread;> continues to be available when you
314 ask for -Duse5005threads, bugs and all.
316 =head2 New Configure flags
318 The following new flags may be enabled on the Configure command line
319 by running Configure with C<-Dflag>.
328 =head2 -Dusethreads and -Duse64bits now more daring
330 The Configure options enabling the use of threads and the use of
331 64-bitness are now more daring in the sense that they no more have an
332 explicit list of operating systems of known threads/64-bit
333 capabilities. In other words: if your operating system has the
334 necessary APIs and datatypes, you should be able just to go ahead and
335 use them, for threads by Configure -Dusethreads, and for 64 bits
336 either explicitly by Configure -Duse64bits or implicitly if your
337 system has 64 bit wide datatypes. See also L<"64-bit support">.
341 Some platforms have "long doubles", floating point numbers of even
342 larger range than ordinary "doubles". To enable using long doubles for
343 Perl's scalars, use -Duselongdouble.
347 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
348 See also L<"64-bit support">.
350 =head2 -Duselargefiles
352 Some platforms support large files, files larger than two gigabytes.
353 See L<"Large file support"> for more information.
355 =head2 installusrbinperl
357 You can use "Configure -Uinstallusrbinperl" which causes installperl
358 to skip installing perl also as /usr/bin/perl. This is useful if you
359 prefer not to modify /usr/bin for some reason or another but harmful
360 because many scripts assume to find Perl in /usr/bin/perl.
364 You can use "Configure -Dusesocks" which causes Perl to probe
365 for the SOCKS (v5, not v4) proxy protocol library,
366 http://www.socks.nec.com/
370 You can "post-edit" the Configure variables using the Configure C<-A>
371 flag. The editing happens immediately after the platform specific
372 hints files have been processed but before the actual configuration
373 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
375 =head2 Enhanced Installation Directories
377 The installation structure has been enriched to improve the support for
378 maintaining multiple versions of perl, to provide locations for
379 vendor-supplied modules and scripts, and to ease maintenance of
380 locally-added modules and scripts. See the section on Installation
381 Directories in the INSTALL file for complete details. For most users
382 building and installing from source, the defaults should be fine.
386 =head2 Unicode and UTF-8 support
388 Perl can optionally use UTF-8 as its internal representation for character
389 strings. The C<utf8> and C<bytes> pragmas are used to control this support
390 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
393 =head2 Interpreter cloning, threads, and concurrency
395 WARNING: This is an experimental feature in a pre-alpha state. Use
398 Perl 5.005_63 introduces the beginnings of support for running multiple
399 interpreters concurrently in different threads. In conjunction with
400 the perl_clone() API call, which can be used to selectively duplicate
401 the state of any given interpreter, it is possible to compile a
402 piece of code once in an interpreter, clone that interpreter
403 one or more times, and run all the resulting interpreters in distinct
406 On Windows, this feature is used to emulate fork() at the interpreter
407 level. See L<perlfork>.
409 This feature is still in evolution. It is eventually meant to be used
410 to selectively clone a subroutine and data reachable from that
411 subroutine in a separate interpreter and run the cloned subroutine
412 in a separate thread. Since there is no shared data between the
413 interpreters, little or no locking will be needed (unless parts of
414 the symbol table are explicitly shared). This is obviously intended
415 to be an easy-to-use replacement for the existing threads support.
417 Support for cloning interpreters and interpreter concurrency can be
418 enabled using the -Dusethreads Configure option (see win32/Makefile for
419 how to enable it on Windows.) The resulting perl executable will be
420 functionally identical to one that was built with -Dmultiplicity, but
421 the perl_clone() API call will only be available in the former.
423 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
424 Perl source code changes that provide a clear separation between the op tree
425 and the data it operates with. The former is considered immutable, and can
426 therefore be shared between an interpreter and all of its clones, while the
427 latter is considered local to each interpreter, and is therefore copied for
430 Note that building Perl with the -Dusemultiplicity Configure option
431 is adequate if you wish to run multiple B<independent> interpreters
432 concurrently in different threads. -Dusethreads only provides the
433 additional functionality of the perl_clone() API call and other
434 support for running B<cloned> interpreters concurrently.
436 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
439 =head2 Lexically scoped warning categories
441 You can now control the granularity of warnings emitted by perl at a finer
442 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
445 =head2 Lvalue subroutines
447 WARNING: This is an experimental feature.
450 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
451 Tuomas Lukka <lukka@iki.fi>)]
453 =head2 "our" declarations
455 An "our" declaration introduces a value that can be best understood
456 as a lexically scoped symbolic alias to a global variable in the
457 package that was current where the variable was declared. This is
458 mostly useful as an alternative to the C<vars> pragma, but also provides
459 the opportunity to introduce typing and other attributes for such
460 variables. See L<perlfunc/our>.
462 =head2 Support for strings represented as a vector of ordinals
464 Literals of the form v1.2.3.4 are now parsed as a string comprised of
465 of characters with the specified ordinals. This is an alternative, more
466 readable way to construct (possibly unicode) strings instead of
467 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">.
469 Strings written in this form are also useful to represent version "numbers".
470 It is easy to compare such version "numbers" (which are really just plain
471 strings) using any of the usual string comparison operators C<eq>, C<ne>,
472 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
475 In conjunction with the new C<$^V> magic variable (which contains
476 the perl version as a string), such literals can be used as a readable way
477 to check if you're running a particular version of Perl:
479 # this will parse in older versions of Perl also
480 if ($^V and $^V gt v5.5.640) {
481 # new features supported
484 C<require> and C<use> also have some special magic to support such literals.
485 They will be interpreted as a version rather than as a module name:
487 require v5.6.0; # croak if $^V lt v5.6.0
488 use v5.6.0; # same, but croaks at compile-time
490 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
491 to print ordinals of characters in arbitrary strings:
493 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
494 printf "%*vX", ":", $addr; # formats IPv6 address
495 printf "%*vb", "", $bits; # displays bitstring as contiguous 0's and 1's
497 See L<perlop/"Strings of Character"> for additional information.
499 =head2 Weak references
501 WARNING: This is an experimental feature.
503 In previous versions of Perl, you couldn't cache objects so as
504 to allow them to be deleted if the last reference from outside
505 the cache is deleted. The reference in the cache would hold a
506 reference count on the object and the objects would never be
509 Another familiar problem is with circular references. When an
510 object references itself, its reference count would never go
511 down to zero, and it would not get destroyed until the program
514 Weak references solve this by allowing you to "weaken" any
515 reference, that is, make it not count towards the reference count.
516 When the last non-weak reference to an object is deleted, the object
517 is destroyed and all the weak references to the object are
518 automatically undef-ed.
520 To use this feature, you need the WeakRef package from CPAN, which
521 contains additional documentation.
523 change#3385, also need perlguts documentation
524 [TODO - Tuomas Lukka <lukka@iki.fi>]
526 =head2 File globbing implemented internally
528 WARNING: This is currently an experimental feature. Interfaces and
529 implementation are likely to change.
531 Perl now uses the File::Glob implementation of the glob() operator
532 automatically. This avoids using an external csh process and the
533 problems associated with it.
535 =head2 Binary numbers supported
537 Binary numbers are now supported as literals, in s?printf formats, and
541 printf "The answer is: %b\n", oct("0b101010");
543 =head2 Some arrows may be omitted in calls through references
545 Perl now allows the arrow to be omitted in many constructs
546 involving subroutine calls through references. For example,
547 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
548 This is rather similar to how the arrow may be omitted from
549 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
550 required for C<foo(10)-E<gt>('bar')>.
552 =head2 exists() is supported on subroutine names
554 The exists() builtin now works on subroutine names. A subroutine
555 is considered to exist if it has been declared (even if implicitly).
556 See L<perlfunc/exists> for examples.
558 =head2 exists() and delete() are supported on array elements
560 The exists() and delete() builtins now work on simple arrays as well.
561 The behavior is similar to that on hash elements.
563 exists() can be used to check whether an array element has been
564 initialized. This avoids autovivifying array elements that don't exist.
565 If the array is tied, the EXISTS() method in the corresponding tied
566 package will be invoked.
568 delete() may be used to remove an element from the array and return
569 it. The array element at that position returns to its unintialized
570 state, so that testing for the same element with exists() will return
571 false. If the element happens to be the one at the end, the size of
572 the array also shrinks up to the highest element that tests true for
573 exists(), or 0 if none such is found. If the array is tied, the DELETE()
574 method in the corresponding tied package will be invoked.
576 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
578 =head2 syswrite() ease-of-use
580 The length argument of C<syswrite()> has become optional.
582 =head2 File and directory handles can be autovivified
584 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
585 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
586 socket(), and accept()) now autovivify a file or directory handle
587 if the handle passed to them is an uninitialized scalar variable. This
588 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
589 to be used to create filehandles that will conveniently be closed
590 automatically when the scope ends, provided there are no other references
591 to them. This largely eliminates the need for typeglobs when opening
592 filehandles that must be passed around, as in the following example:
596 or die "Can't open '@_': $!";
601 my $f = myopen("</etc/motd");
603 # $f implicitly closed here
606 [TODO - this idiom needs more pod penetration]
608 =head2 64-bit support
610 All platforms that have 64-bit integers either (a) natively as longs
611 or ints (b) via special compiler flags (c) using long long are able to
612 use "quads" (64-integers) as follows:
618 constants (decimal, hexadecimal, octal, binary) in the code
622 arguments to oct() and hex()
626 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
634 pack() and unpack() "q" and "Q" formats
638 in basic arithmetics: + - * / %
642 vec() (but see the below note about bit arithmetics)
646 Note that unless you have the case (a) you will have to configure
647 and compile Perl using the -Duse64bits Configure flag.
649 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
650 64-bit clean, they are explictly forced to be 32-bit because of
651 tangled backward compatibility issues. This limitation is subject to
652 change. Bit arithmetics for bit vector scalars (created by vec()) are
653 not limited in their width, you can use the & | ^ ~ operators on such
656 Last but not least: note that due to Perl's habit of always using
657 floating point numbers the quads are still not true integers.
658 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
659 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
660 are silently promoted to floating point numbers, after which they will
661 start losing precision (their lower digits).
663 =head2 Large file support
665 If you have filesystems that support "large files" (files larger than
666 2 gigabytes), you may now also be able to create and access them from
667 Perl. You have to use Configure -Duselargefiles. Turning on the
668 large file support turns on also the 64-bit support on many platforms.
669 Beware that unless your filesystem also supports "sparse files" seeking
670 to umpteen petabytes may be unadvisable.
672 Note that in addition to requiring a proper file system to do large
673 files you may also need to adjust your per-process (or your
674 per-system, or per-process-group, or per-user-group) maximum filesize
675 limits before running Perl scripts that try to handle large files,
676 especially if you intend to write such files.
678 Finally, in addition to your process/process group maximum filesize
679 limits, you may have quota limits on your filesystems that stop you
680 (your user id or your user group id) from using large files.
682 Adjusting your process/user/group/file system/operating system limits
683 is outside the scope of Perl core language. For process limits, you
684 may try increasing the limits using your shell's limits/limit/ulimit
685 command before running Perl. The BSD::Resource extension (not
686 included with the standard Perl distribution) may also be of use, it
687 offers the getrlimit/setrlimit interface that can be used to adjust
688 process resource usage limits, including the maximum filesize limit.
692 In some systems you may be able to use long doubles to enhance the
693 range and precision of your double precision floating point numbers
694 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
695 this support (if it is available).
699 You can "Configure -Dusemorebits" to turn on both the 64-bit support
700 and the long double support.
702 =head2 Enhanced support for sort() subroutines
704 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
705 now be used as sort subroutines. In either case, the two elements to
706 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
708 For unprototyped sort subroutines, the historical behavior of passing
709 the elements to be compared as the global variables $a and $b remains
712 =head2 Better syntax checks on parenthesized unary operators
716 print defined(&foo,&bar,&baz);
717 print uc("foo","bar","baz");
720 used to be accidentally allowed in earlier versions, and produced
721 unpredictable behaviour. Some produced ancillary warnings
722 when used in this way; others silently did the wrong thing.
724 The parenthesized forms of most unary operators that expect a single
725 argument now ensure that they are not called with more than one
726 argument, making the cases shown above syntax errors. The usual
729 print defined &foo, &bar, &baz;
730 print uc "foo", "bar", "baz";
733 remains unchanged. See L<perlop>.
735 =head2 POSIX character class syntax [: :] supported
737 For example to match alphabetic characters use /[[:alpha:]]/.
738 See L<perlre> for details.
740 =head2 Improved C<qw//> operator
742 The C<qw//> operator is now evaluated at compile time into a true list
743 instead of being replaced with a run time call to C<split()>. This
744 removes the confusing misbehaviour of C<qw//> in scalar context, which
745 had inherited that behaviour from split().
749 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
751 now correctly prints "3|a", instead of "2|a".
753 =head2 pack() format 'Z' supported
755 The new format type 'Z' is useful for packing and unpacking null-terminated
756 strings. See L<perlfunc/"pack">.
758 =head2 pack() format modifier '!' supported
760 The new format type modifier '!' is useful for packing and unpacking
761 native shorts, ints, and longs. See L<perlfunc/"pack">.
763 =head2 pack() and unpack() support counted strings
765 The template character '/' can be used to specify a counted string
766 type to be packed or unpacked. See L<perlfunc/"pack">.
768 =head2 Comments in pack() templates
770 The '#' character in a template introduces a comment up to
771 end of the line. This facilitates documentation of pack()
774 =head2 $^X variables may now have names longer than one character
776 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
777 error. Now variable names that begin with a control character may be
778 arbitrarily long. However, for compatibility reasons, these variables
779 I<must> be written with explicit braces, as C<${^XY}> for example.
780 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
781 than one control character, such as C<${^XY^Z}>, are illegal.
783 The old syntax has not changed. As before, `^X' may be either a
784 literal control-X character or the two-character sequence `caret' plus
785 `X'. When braces are omitted, the variable name stops after the
786 control character. Thus C<"$^XYZ"> continues to be synonymous with
787 C<$^X . "YZ"> as before.
789 As before, lexical variables may not have names beginning with control
790 characters. As before, variables whose names begin with a control
791 character are always forced to be in package `main'. All such variables
792 are reserved for future extensions, except those that begin with
793 C<^_>, which may be used by user programs and are guaranteed not to
794 acquire special meaning in any future version of Perl.
796 =head2 C<use attrs> implicit in subroutine attributes
798 Formerly, if you wanted to mark a subroutine as being a method call or
799 as requiring an automatic lock() when it is entered, you had to declare
800 that with a C<use attrs> pragma in the body of the subroutine.
801 That can now be accomplished with declaration syntax, like this:
803 sub mymethod : locked method ;
805 sub mymethod : locked method {
809 sub othermethod :locked :method ;
811 sub othermethod :locked :method {
816 (Note how only the first C<:> is mandatory, and whitespace surrounding
817 the C<:> is optional.)
819 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
820 with the stubs they provide. See L<attributes>.
822 =head2 Regular expression improvements
824 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
825 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
827 =head2 Overloading improvements
830 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
832 =head2 open() with more than two arguments
834 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
836 =head2 Support for interpolating named characters
839 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
841 =head2 Experimental support for user-hooks in @INC
843 [TODO - Ken Fox <kfox@ford.com>]
845 =head2 C<require> and C<do> may be overridden
847 C<require> and C<do 'file'> operations may be overridden locally
848 by importing subroutines of the same name into the current package
849 (or globally by importing them into the CORE::GLOBAL:: namespace).
850 Overriding C<require> will also affect C<use>, provided the override
851 is visible at compile-time.
852 See L<perlsub/"Overriding Built-in Functions">.
854 =head2 New variable $^C reflects C<-c> switch
856 C<$^C> has a boolean value that reflects whether perl is being run
857 in compile-only mode (i.e. via the C<-c> switch). Since
858 BEGIN blocks are executed under such conditions, this variable
859 enables perl code to determine whether actions that make sense
860 only during normal running are warranted. See L<perlvar>.
862 =head2 New variable $^V contains Perl version in v5.6.0 format
864 C<$^V> contains the Perl version number as a string comprised of
865 characters whose ordinals match the version numbers, so that it may
866 be used in string comparisons.
868 See C<Support for strings represented as a vector of ordinals> for an
871 =head2 Optional Y2K warnings
873 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
874 it emits optional warnings when concatenating the number 19
877 This behavior must be specifically enabled when running Configure.
878 See F<INSTALL> and F<README.Y2K>.
880 =head1 Significant bug fixes
882 =head2 E<lt>HANDLEE<gt> on empty files
884 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
885 zero length (instead of C<undef>, as it used to) the first time the
886 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
889 This means that the following will append "foo" to an empty file (it used
892 perl -0777 -pi -e 's/^/foo/' empty_file
896 perl -pi -e 's/^/foo/' empty_file
898 is unchanged (it continues to leave the file empty).
900 =head2 C<eval '...'> improvements
902 Line numbers (as reflected by caller() and most diagnostics) within
903 C<eval '...'> were often incorrect when here documents were involved.
904 This has been corrected.
906 Lexical lookups for variables appearing in C<eval '...'> within
907 functions that were themselves called within an C<eval '...'> were
908 searching the wrong place for lexicals. The lexical search now
909 correctly ends at the subroutine's block boundary.
911 Parsing of here documents used to be flawed when they appeared as
912 the replacement expression in C<eval 's/.../.../e'>. This has
915 =head2 All compilation errors are true errors
917 Some "errors" encountered at compile time were by neccessity
918 generated as warnings followed by eventual termination of the
919 program. This enabled more such errors to be reported in a
920 single run, rather than causing a hard stop at the first error
921 that was encountered.
923 The mechanism for reporting such errors has been reimplemented
924 to queue compile-time errors and report them at the end of the
925 compilation as true errors rather than as warnings. This fixes
926 cases where error messages leaked through in the form of warnings
927 when code was compiled at run time using C<eval STRING>, and
928 also allows such errors to be reliably trapped using __DIE__ hooks.
930 =head2 Automatic flushing of output buffers
932 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
933 of all files opened for output when the operation
934 was attempted. This mostly eliminates confusing
935 buffering mishaps suffered by users unaware of how Perl internally
938 =head2 Better diagnostics on meaningless filehandle operations
940 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
941 are compile time errors. Attempting to read from filehandles that
942 were opened only for writing will now produce warnings (just as
943 writing to read-only filehandles does).
945 =head2 Where possible, buffered data discarded from duped input filehandle
947 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
948 was previously read and buffered in C<OLD> before duping the handle.
949 On platforms where doing this is allowed, the next read operation
950 on C<NEW> will return the same data as the corresponding operation
951 on C<OLD>. Formerly, it would have returned the data from the start
952 of the following disk block instead.
954 =head2 eof() has the same old magic as <>
956 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
957 yet been made. C<eof()> has been changed to have a little magic of its
958 own, it now opens the C<E<lt>E<gt>> files.
960 =head2 system(), backticks and pipe open now reflect exec() failure
962 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
963 etc., are implemented via fork() and exec(). When the underlying
964 exec() fails, earlier versions did not report the error properly,
965 since the exec() happened to be in a different process.
967 The child process now communicates with the parent about the
968 error in launching the external command, which allows these
969 constructs to return with their usual error value and set $!.
971 =head2 Implicitly closed filehandles are safer
973 Sometimes implicitly closed filehandles (as when they are localized,
974 and Perl automatically closes them on exiting the scope) could
975 inadvertently set $? or $!. This has been corrected.
977 =head2 C<(\$)> prototype and C<$foo{a}>
979 An scalar reference prototype now correctly allows a hash or
980 array element in that slot.
982 =head2 Pseudo-hashes work better
984 Dereferencing some types of reference values in a pseudo-hash,
985 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
988 When applied to a pseudo-hash element, exists() now reports whether
989 the specified value exists, not merely if the key is valid.
991 delete() now works on pseudo-hashes. When given a pseudo-hash element
992 or slice it deletes the values corresponding to the keys (but not the keys
993 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
995 =head2 C<goto &sub> and AUTOLOAD
997 The C<goto &sub> construct works correctly when C<&sub> happens
1000 =head2 C<-bareword> allowed under C<use integer>
1002 The autoquoting of barewords preceded by C<-> did not work
1003 in prior versions when the C<integer> pragma was enabled.
1004 This has been fixed.
1006 =head2 Boolean assignment operators are legal lvalues
1008 Constructs such as C<($a ||= 2) += 1> are now allowed.
1010 =head2 C<sort $coderef @foo> allowed
1012 sort() did not accept a subroutine reference as the comparison
1013 function in earlier versions. This is now permitted.
1015 =head2 Failures in DESTROY()
1017 When code in a destructor threw an exception, it went unnoticed
1018 in earlier versions of Perl, unless someone happened to be
1019 looking in $@ just after the point the destructor happened to
1020 run. Such failures are now visible as warnings when warnings are
1023 =head2 Locale bugs fixed
1025 printf() and sprintf() previously reset the numeric locale
1026 back to the default "C" locale. This has been fixed.
1028 Numbers formatted according to the local numeric locale
1029 (such as using a decimal comma instead of a decimal dot) caused
1030 "isn't numeric" warnings, even while the operations accessing
1031 those numbers produced correct results. The warnings are gone.
1035 The C<eval 'return sub {...}'> construct could sometimes leak
1036 memory. This has been fixed.
1038 Operations that aren't filehandle constructors used to leak memory
1039 when used on invalid filehandles. This has been fixed.
1041 Constructs that modified C<@_> could fail to deallocate values
1042 in C<@_> and thus leak memory. This has been corrected.
1044 =head2 Spurious subroutine stubs after failed subroutine calls
1046 Perl could sometimes create empty subroutine stubs when a
1047 subroutine was not found in the package. Such cases stopped
1048 later method lookups from progressing into base packages.
1049 This has been corrected.
1051 =head2 Consistent numeric conversions
1054 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1056 =head2 Taint failures under C<-U>
1058 When running in unsafe mode, taint violations could sometimes
1059 cause silent failures. This has been fixed.
1061 =head2 END blocks and the C<-c> switch
1063 Prior versions used to run BEGIN B<and> END blocks when Perl was
1064 run in compile-only mode. Since this is typically not the expected
1065 behavior, END blocks are not executed anymore when the C<-c> switch
1068 See L<CHECK blocks> for how to run things when the compile phase ends.
1070 =head2 Potential to leak DATA filehandles
1072 Using the C<__DATA__> token creates an implicit filehandle to
1073 the file that contains the token. It is the program's
1074 responsibility to close it when it is done reading from it.
1076 This caveat is now better explained in the documentation.
1079 =head2 Diagnostics follow STDERR
1081 Diagnostic output now goes to whichever file the C<STDERR> handle
1082 is pointing at, instead of always going to the underlying C runtime
1083 library's C<stderr>.
1085 =head2 Other fixes for better diagnostics
1087 Line numbers are no longer suppressed (under most likely circumstances)
1088 during the global destruction phase.
1090 Diagnostics emitted from code running in threads other than the main
1091 thread are now accompanied by the thread ID.
1093 Embedded null characters in diagnostics now actually show up. They
1094 used to truncate the message in prior versions.
1096 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1097 if sort() is encountered in package foo.
1099 Unrecognized alphabetic escapes encountered when parsing quote
1100 constructs now generate a warning, since they may take on new
1101 semantics in later versions of Perl.
1103 =head1 Performance enhancements
1105 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1107 Many common sort() operations using a simple inlined block are now
1108 optimized for faster performance.
1110 =head2 Optimized assignments to lexical variables
1112 Certain operations in the RHS of assignment statements have been
1113 optimized to directly set the lexical variable on the LHS,
1114 eliminating redundant copying overheads.
1116 =head2 Method lookups optimized
1118 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1120 =head2 Faster mechanism to invoke XSUBs
1123 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1125 =head2 Perl_malloc() improvements
1128 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1130 =head2 Faster subroutine calls
1132 Minor changes in how subroutine calls are handled internally
1133 provide marginal improvements in performance.
1135 =head1 Platform specific changes
1137 =head2 Additional supported platforms
1143 VM/ESA is now supported.
1147 Siemens BS2000 is now supported under the POSIX Shell.
1151 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1156 GNU/Hurd is now supported.
1160 Rhapsody is now supported.
1164 EPOC is is now supported (on Psion 5).
1174 Perl now works with djgpp 2.02 (and 2.03 alpha).
1178 Environment variable names are not converted to uppercase any more.
1182 Wrong exit code from backticks now fixed.
1186 This port is still using its own builtin globbing.
1192 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1196 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1200 Site library searches failed to look for ".../site/5.XXX/lib"
1201 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1203 When given a pathname that consists only of a drivename, such
1204 as C<A:>, opendir() and stat() now use the current working
1205 directory for the drive rather than the drive root.
1207 The builtin XSUB functions in the Win32:: namespace are
1208 documented. See L<Win32>.
1210 $^X now contains the full path name of the running executable.
1212 A Win32::GetLongPathName() function is provided to complement
1213 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1215 POSIX::uname() is supported.
1217 system(1,...) now returns true process IDs rather than process
1218 handles. kill() accepts any real process id, rather than strictly
1219 return values from system(1,...).
1221 The C<Shell> module is supported.
1223 Rudimentary support for building under command.com in Windows 95
1226 Scripts are read in binary mode by default to allow ByteLoader (and
1227 the filter mechanism in general) to work properly. For compatibility,
1228 the DATA filehandle will be set to text mode if a carriage return is
1229 detected at the end of the line containing the __END__ or __DATA__
1230 token; if not, the DATA filehandle will be left open in binary mode.
1231 Earlier versions always opened the DATA filehandle in text mode.
1233 The glob() operator is implemented via the L<File::Glob> extension,
1234 which supports glob syntax of the C shell. This increases the flexibility
1235 of the glob() operator, but there may be compatibility issues for
1236 programs that relied on the older globbing syntax. If you want to
1237 preserve compatibility with the older syntax, you might want to put
1238 a C<use File::DosGlob;> in your program. For details and compatibility
1239 information, see L<File::Glob>.
1249 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1253 IO constants (SEEK_*, _IO*).
1257 Directory-related IO methods (new, read, close, rewind, tied delete).
1259 =item lib/io_multihomed
1261 INET sockets with multi-homed hosts.
1273 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1277 File test operators.
1281 Verify operations that access pad objects (lexicals and temporaries).
1285 Verify C<exists &sub> operations.
1289 =head1 Modules and Pragmata
1297 While used internally by Perl as a pragma, this module also
1298 provides a way to fetch subroutine and variable attributes.
1303 The Perl Compiler suite has been extensively reworked for this
1306 [TODO - Vishal Bhatia <vishal@gol.com>,
1307 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1311 The ByteLoader is a dedicated extension to generate and run
1312 Perl bytecode. See L<ByteLoader>.
1316 References can now be used.
1318 The new version also allows a leading underscore in constant names, but
1319 disallows a double leading underscore (as in "__LINE__"). Some other names
1320 are disallowed or warned against, including BEGIN, END, etc. Some names
1321 which were forced into main:: used to fail silently in some cases; now they're
1322 fatal (outside of main::) and an optional warning (inside of main::).
1323 The ability to detect whether a constant had been set with a given name has
1331 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1335 A C<Maxdepth> setting can be specified to avoid venturing
1336 too deeply into deep data structures. See L<Data::Dumper>.
1338 Dumping C<qr//> objects works correctly.
1342 C<DB> is an experimental module that exposes a clean abstraction
1343 to Perl's debugging API.
1347 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1348 See C<ext/DB_File/Changes>.
1352 Devel::DProf, a Perl source code profiler has been added. See
1353 L<Devel::DProf> and L<dprofpp>.
1357 The Dumpvalue module provides screen dumps of Perl data.
1361 Overall, Benchmark results exhibit lower average error and better timing
1364 You can now run tests for I<n> seconds instead of guessing the right
1365 number of tests to run: e.g. timethese(-5, ...) will run each
1366 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1367 means "for at least 3 CPU seconds". The output format has also
1368 changed. For example:
1370 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1372 will now output something like this:
1374 Benchmark: running a, b, each for at least 5 CPU seconds...
1375 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1376 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1378 New features: "each for at least N CPU seconds...", "wallclock secs",
1379 and the "@ operations/CPU second (n=operations)".
1381 timethese() now returns a reference to a hash of Benchmark objects containing
1382 the test results, keyed on the names of the tests.
1384 timethis() now returns the iterations field in the Benchmark result object
1387 timethese(), timethis(), and the new cmpthese() (see below) can also take
1388 a format specifier of 'none' to suppress output.
1390 A new function countit() is just like timeit() except that it takes a
1391 TIME instead of a COUNT.
1393 A new function cmpthese() prints a chart comparing the results of each test
1394 returned from a timethese() call. For each possible pair of tests, the
1395 percentage speed difference (iters/sec or seconds/iter) is shown.
1397 For other details, see L<Benchmark>.
1401 The Devel::Peek module provides access to the internal representation
1402 of Perl variables and data. It is a data debugging tool for the XS programmer.
1406 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1409 =item ExtUtils::MakeMaker
1411 change#4135, also needs docs in module pod
1412 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1416 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1417 large file (more than 4GB) access Note that the O_LARGEFILE is
1418 automatically/transparently added to sysopen() flags if large file
1419 support has been configured), Free/Net/OpenBSD locking behaviour flags
1420 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1421 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1422 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1423 The chmod()/stat() S_IF* constants and S_IS* functions are available
1424 via the C<:mode> tag.
1429 A compare_text() function has been added, which allows custom
1430 comparison functions. See L<File::Compare>.
1434 File::Find now works correctly when the wanted() function is either
1435 autoloaded or is a symbolic reference.
1437 A bug that caused File::Find to lose track of the working directory
1438 when pruning top-level directories has been fixed.
1440 File::Find now also supports several other options to control its
1441 behavior. It can follow symbolic links if the C<follow> option is
1442 specified. Enabling the C<no_chdir> option will make File::Find skip
1443 changing the current directory when walking directories. The C<untaint>
1444 flag can be useful when running with taint checks enabled.
1450 This extension implements BSD-style file globbing. By default,
1451 it will also be used for the internal implementation of the glob()
1452 operator. See L<File::Glob>.
1456 New methods have been added to the File::Spec module: devnull() returns
1457 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1458 the temp directory (normally /tmp on Unix). There are now also methods
1459 to convert between absolute and relative filenames: abs2rel() and
1460 rel2abs(). For compatibility with operating systems that specify volume
1461 names in file paths, the splitpath(), splitdir(), and catdir() methods
1464 =item File::Spec::Functions
1466 The new File::Spec::Functions modules provides a function interface
1467 to the File::Spec module. Allows shorthand
1469 $fullname = catfile($dir1, $dir2, $file);
1473 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1477 Getopt::Long licensing has changed to allow the Perl Artistic License
1478 as well as the GPL. It used to be GPL only, which got in the way of
1479 non-GPL applications that wanted to use Getopt::Long.
1481 Getopt::Long encourages the use of Pod::Usage to produce help
1482 messages. For example:
1488 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1489 pod2usage(1) if $help;
1490 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1496 sample - Using GetOpt::Long and Pod::Usage
1500 sample [options] [file ...]
1503 -help brief help message
1504 -man full documentation
1512 Print a brief help message and exits.
1516 Prints the manual page and exits.
1522 B<This program> will read the given input file(s) and do someting
1523 useful with the contents thereof.
1527 See L<Pod::Usage> for details.
1529 A bug that prevented the non-option call-back E<lt>E<gt> from being
1530 specified as the first argument has been fixed.
1532 To specify the characters E<lt> and E<gt> as option starters, use
1533 E<gt>E<lt>. Note, however, that changing option starters is strongly
1538 write() and syswrite() will now accept a single-argument
1539 form of the call, for consistency with Perl's syswrite().
1541 You can now create a TCP-based IO::Socket::INET without forcing
1542 a connect attempt. This allows you to configure its options
1543 (like making it non-blocking) and then call connect() manually.
1545 A bug that prevented the IO::Socket::protocol() accessor
1546 from ever returning the correct value has been corrected.
1550 Java Perl Lingo is now distributed with Perl. See jpl/README
1551 for more information.
1555 C<use lib> now weeds out any trailing duplicate entries.
1556 C<no lib> removes all named entries.
1560 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1561 and C<~> are now supported on bigints.
1565 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1566 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1570 A little bit of radial trigonometry (cylindrical and spherical),
1571 radial coordinate conversions, and the great circle distance were added.
1573 =item Pod::Parser, Pod::InputObjects
1575 Pod::Parser is a base class for parsing and selecting sections of
1576 pod documentation from an input stream. This module takes care of
1577 identifying pod paragraphs and commands in the input and hands off the
1578 parsed paragraphs and commands to user-defined methods which are free
1579 to interpret or translate them as they see fit.
1581 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1582 for advanced users of Pod::Parser that need more about a command besides
1585 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1586 "base parser code" recommended for use by all pod2xxx translators.
1587 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1588 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1589 underway. For any questions or comments about pod parsing and translating
1590 issues and utilities, please use the pod-people@perl.org mailing list.
1592 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1594 =item Pod::Checker, podchecker
1596 This utility checks pod files for correct syntax, according to
1597 L<perlpod>. Obvious errors are flagged as such, while warnings are
1598 printed for mistakes that can be handled gracefully. The checklist is
1599 not complete yet. See L<Pod::Checker>.
1601 =item Pod::ParseUtils, Pod::Find
1603 These modules provide a set of gizmos that are useful mainly for pod
1604 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1605 returns found pod files, along with their canonical names (like
1606 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1607 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1608 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1609 (for caching information about pod files, e.g. link nodes).
1611 =item Pod::Select, podselect
1613 Pod::Select is a subclass of Pod::Parser which provides a function
1614 named "podselect()" to filter out user-specified sections of raw pod
1615 documentation from an input stream. podselect is a script that provides
1616 access to Pod::Select from other scripts to be used as a filter.
1619 =item Pod::Usage, pod2usage
1621 Pod::Usage provides the function "pod2usage()" to print usage messages for
1622 a Perl script based on its embedded pod documentation. The pod2usage()
1623 function is generally useful to all script authors since it lets them
1624 write and maintain a single source (the pods) for documentation, thus
1625 removing the need to create and maintain redundant usage message text
1626 consisting of information already in the pods.
1628 There is also a pod2usage script which can be used from other kinds of
1629 scripts to print usage messages from pods (even for non-Perl scripts
1630 with pods embedded in comments).
1632 For details and examples, please see L<Pod::Usage>.
1634 =item Pod::Text and Pod::Man
1636 [TODO - Russ Allbery <rra@stanford.edu>]
1640 An EXISTS method has been added to this module (and sdbm_exists() has
1641 been added to the underlying sdbm library), so one can now call exists
1642 on an SDBM_File tied hash and get the correct result, rather than a
1645 A bug that may have caused data loss when more than one disk block
1646 happens to be read from the database in a single FETCH() has been
1651 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1652 no longer requires syslog.ph to exist.
1656 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1657 uname() if they exist.
1661 The timelocal() and timegm() functions used to silently return bogus
1662 results when the date fell outside the machine's integer range. They
1663 now consistently croak() if the date falls in an unsupported range.
1667 The error return value in list context has been changed for all functions
1668 that return a list of values. Previously these functions returned a list
1669 with a single element C<undef> if an error occurred. Now these functions
1670 return the empty list in these situations. This applies to the following
1676 The remaining functions are unchanged and continue to return C<undef> on
1677 error even in list context.
1679 The Win32::SetLastError(ERROR) function has been added as a complement
1680 to the Win32::GetLastError() function.
1682 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1683 pathname for FILENAME in scalar context. In list context it returns
1684 a two-element list containing the fully qualified directory name and
1685 the filename. See L<Win32>.
1689 A new feature called "DBM Filters" has been added to all the
1690 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1691 DBM Filters add four new methods to each DBM module:
1698 These can be used to filter key-value pairs before the pairs are
1699 written to the database or just after they are read from the database.
1700 See L<perldbmfilter> for further information.
1706 C<use attrs> is now obsolete, and is only provided for
1707 backward-compatibility. It's been replaced by the C<sub : attributes>
1708 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1710 C<use utf8> to enable UTF-8 and Unicode support.
1712 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1715 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1716 ...). Currently only one subpragma implemented, "use filetest
1717 'access';", that uses access(2) or equivalent to check permissions
1718 instead of using stat(2) as usual. This matters in filesystems
1719 where there are ACLs (access control lists): the stat(2) might lie,
1720 but access(2) knows better.
1722 =head1 Utility Changes
1726 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1730 C<perlcc> now supports the C and Bytecode backends. By default,
1731 it generates output from the simple C backend rather than the
1732 optimized C backend.
1734 Support for non-Unix platforms has been improved.
1739 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1741 =head1 Documentation Changes
1747 The official list of public Perl API functions.
1749 =item perlcompile.pod
1751 An introduction to using the Perl Compiler suite.
1753 =item perlfilter.pod
1755 An introduction to writing Perl source filters.
1759 Some guidelines for hacking the Perl source code.
1761 =item perlintern.pod
1763 A list of internal functions in the Perl source code.
1764 (List is currently empty.)
1766 =item perlopentut.pod
1768 A tutorial on using open() effectively.
1770 =item perlreftut.pod
1772 A tutorial that introduces the essentials of references.
1776 A tutorial on managing class data for object modules.
1778 =item perlunicode.pod
1780 An introduction to Unicode support features in Perl.
1784 =head1 New or Changed Diagnostics
1788 =item "%s" variable %s masks earlier declaration in same %s
1790 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1791 effectively eliminating all access to the previous instance. This is almost
1792 always a typographical error. Note that the earlier variable will still exist
1793 until the end of the scope or until all closure referents to it are
1796 =item "my sub" not yet implemented
1798 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1801 =item "our" variable %s redeclared
1803 (W) You seem to have already declared the same global once before in the
1804 current lexical scope.
1806 =item '!' allowed only after types %s
1808 (F) The '!' is allowed in pack() and unpack() only after certain types.
1809 See L<perlfunc/pack>.
1811 =item / cannot take a count
1813 (F) You had an unpack template indicating a counted-length string,
1814 but you have also specified an explicit size for the string.
1815 See L<perlfunc/pack>.
1817 =item / must be followed by a, A or Z
1819 (F) You had an unpack template indicating a counted-length string,
1820 which must be followed by one of the letters a, A or Z
1821 to indicate what sort of string is to be unpacked.
1822 See L<perlfunc/pack>.
1824 =item / must be followed by a*, A* or Z*
1826 (F) You had a pack template indicating a counted-length string,
1827 Currently the only things that can have their length counted are a*, A* or Z*.
1828 See L<perlfunc/pack>.
1830 =item / must follow a numeric type
1832 (F) You had an unpack template that contained a '#',
1833 but this did not follow some numeric unpack specification.
1834 See L<perlfunc/pack>.
1836 =item /%s/: Unrecognized escape \\%c passed through
1838 (W) You used a backslash-character combination which is not recognized
1839 by Perl. This combination appears in an interpolated variable or a
1840 C<'>-delimited regular expression. The character was understood literally.
1842 =item /%s/: Unrecognized escape \\%c in character class passed through
1844 (W) You used a backslash-character combination which is not recognized
1845 by Perl inside character classes. The character was understood literally.
1847 =item /%s/ should probably be written as "%s"
1849 (W) You have used a pattern where Perl expected to find a string,
1850 as in the first argument to C<join>. Perl will treat the true
1851 or false result of matching the pattern against $_ as the string,
1852 which is probably not what you had in mind.
1854 =item %s() called too early to check prototype
1856 (W) You've called a function that has a prototype before the parser saw a
1857 definition or declaration for it, and Perl could not check that the call
1858 conforms to the prototype. You need to either add an early prototype
1859 declaration for the subroutine in question, or move the subroutine
1860 definition ahead of the call to get proper prototype checking. Alternatively,
1861 if you are certain that you're calling the function correctly, you may put
1862 an ampersand before the name to avoid the warning. See L<perlsub>.
1864 =item %s argument is not a HASH or ARRAY element
1866 (F) The argument to exists() must be a hash or array element, such as:
1869 $ref->[12]->["susie"]
1871 =item %s argument is not a HASH or ARRAY element or slice
1873 (F) The argument to delete() must be either a hash or array element, such as:
1876 $ref->[12]->["susie"]
1878 or a hash or array slice, such as:
1880 @foo[$bar, $baz, $xyzzy]
1881 @{$ref->[12]}{"susie", "queue"}
1883 =item %s argument is not a subroutine name
1885 (F) The argument to exists() for C<exists &sub> must be a subroutine
1886 name, and not a subroutine call. C<exists &sub()> will generate this error.
1888 =item %s package attribute may clash with future reserved word: %s
1890 (W) A lowercase attribute name was used that had a package-specific handler.
1891 That name might have a meaning to Perl itself some day, even though it
1892 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1895 =item (in cleanup) %s
1897 (W) This prefix usually indicates that a DESTROY() method raised
1898 the indicated exception. Since destructors are usually called by
1899 the system at arbitrary points during execution, and often a vast
1900 number of times, the warning is issued only once for any number
1901 of failures that would otherwise result in the same message being
1904 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1905 could also result in this warning. See L<perlcall/G_KEEPERR>.
1907 =item <> should be quotes
1909 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1912 =item Attempt to join self
1914 (F) You tried to join a thread from within itself, which is an
1915 impossible task. You may be joining the wrong thread, or you may
1916 need to move the join() to some other thread.
1918 =item Bad evalled substitution pattern
1920 (F) You've used the /e switch to evaluate the replacement for a
1921 substitution, but perl found a syntax error in the code to evaluate,
1922 most likely an unexpected right brace '}'.
1924 =item Bad realloc() ignored
1926 (S) An internal routine called realloc() on something that had never been
1927 malloc()ed in the first place. Mandatory, but can be disabled by
1928 setting environment variable C<PERL_BADFREE> to 1.
1930 =item Bareword found in conditional
1932 (W) The compiler found a bareword where it expected a conditional,
1933 which often indicates that an || or && was parsed as part of the
1934 last argument of the previous construct, for example:
1938 It may also indicate a misspelled constant that has been interpreted
1941 use constant TYPO => 1;
1942 if (TYOP) { print "foo" }
1944 The C<strict> pragma is useful in avoiding such errors.
1946 =item Binary number > 0b11111111111111111111111111111111 non-portable
1948 (W) The binary number you specified is larger than 2**32-1
1949 (4294967295) and therefore non-portable between systems. See
1950 L<perlport> for more on portability concerns.
1952 =item Bit vector size > 32 non-portable
1954 (W) Using bit vector sizes larger than 32 is non-portable.
1956 =item Buffer overflow in prime_env_iter: %s
1958 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
1959 %ENV, it encountered a logical name or symbol definition which was too long,
1960 so it was truncated to the string shown.
1962 =item Can't check filesystem of script "%s"
1964 (P) For some reason you can't check the filesystem of the script for nosuid.
1966 =item Can't declare class for non-scalar %s in "%s"
1968 (S) Currently, only scalar variables can declared with a specific class
1969 qualifier in a "my" or "our" declaration. The semantics may be extended
1970 for other types of variables in future.
1972 =item Can't declare %s in "%s"
1974 (F) Only scalar, array, and hash variables may be declared as "my" or
1975 "our" variables. They must have ordinary identifiers as names.
1977 =item Can't ignore signal CHLD, forcing to default
1979 (W) Perl has detected that it is being run with the SIGCHLD signal
1980 (sometimes known as SIGCLD) disabled. Since disabling this signal
1981 will interfere with proper determination of exit status of child
1982 processes, Perl has reset the signal to its default value.
1983 This situation typically indicates that the parent program under
1984 which Perl may be running (e.g. cron) is being very careless.
1986 =item Can't modify non-lvalue subroutine call
1988 (F) Subroutines meant to be used in lvalue context should be declared as
1989 such, see L<perlsub/"Lvalue subroutines">.
1991 =item Can't read CRTL environ
1993 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1994 from the CRTL's internal environment array and discovered the array was
1995 missing. You need to figure out where your CRTL misplaced its environ
1996 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1998 =item Can't remove %s: %s, skipping file
2000 (S) You requested an inplace edit without creating a backup file. Perl
2001 was unable to remove the original file to replace it with the modified
2002 file. The file was left unmodified.
2004 =item Can't return %s from lvalue subroutine
2006 (F) Perl detected an attempt to return illegal lvalues (such
2007 as temporary or readonly values) from a subroutine used as an lvalue.
2008 This is not allowed.
2010 =item Can't weaken a nonreference
2012 (F) You attempted to weaken something that was not a reference. Only
2013 references can be weakened.
2015 =item Character class [:%s:] unknown
2017 (F) The class in the character class [: :] syntax is unknown.
2020 =item Character class syntax [%s] belongs inside character classes
2022 (W) The character class constructs [: :], [= =], and [. .] go
2023 I<inside> character classes, the [] are part of the construct,
2024 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2025 are not currently implemented; they are simply placeholders for
2028 =item Constant is not %s reference
2030 (F) A constant value (perhaps declared using the C<use constant> pragma)
2031 is being dereferenced, but it amounts to the wrong type of reference. The
2032 message indicates the type of reference that was expected. This usually
2033 indicates a syntax error in dereferencing the constant value.
2034 See L<perlsub/"Constant Functions"> and L<constant>.
2036 =item constant(%s): %%^H is not localized
2038 (F) When setting compile-time-lexicalized hash %^H one should set the
2039 corresponding bit of $^H as well.
2041 =item constant(%s): %s
2043 (F) Compile-time-substitutions (such as overloaded constants and
2044 character names) were not correctly set up.
2046 =item defined(@array) is deprecated
2048 (D) defined() is not usually useful on arrays because it checks for an
2049 undefined I<scalar> value. If you want to see if the array is empty,
2050 just use C<if (@array) { # not empty }> for example.
2052 =item defined(%hash) is deprecated
2054 (D) defined() is not usually useful on hashes because it checks for an
2055 undefined I<scalar> value. If you want to see if the hash is empty,
2056 just use C<if (%hash) { # not empty }> for example.
2058 =item Did not produce a valid header
2062 =item Did you mean "local" instead of "our"?
2064 (W) Remember that "our" does not localize the declared global variable.
2065 You have declared it again in the same lexical scope, which seems superfluous.
2067 =item Document contains no data
2071 =item entering effective %s failed
2073 (F) While under the C<use filetest> pragma, switching the real and
2074 effective uids or gids failed.
2076 =item false [] range "%s" in regexp
2078 (W) A character class range must start and end at a literal character, not
2079 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2080 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2083 =item Filehandle %s opened only for output
2085 (W) You tried to read from a filehandle opened only for writing. If you
2086 intended it to be a read/write filehandle, you needed to open it with
2087 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2088 you intended only to read from the file, use "E<lt>". See
2091 =item flock() on closed filehandle %s
2093 (W) The filehandle you're attempting to flock() got itself closed some
2094 time before now. Check your logic flow. flock() operates on filehandles.
2095 Are you attempting to call flock() on a dirhandle by the same name?
2097 =item Global symbol "%s" requires explicit package name
2099 (F) You've said "use strict vars", which indicates that all variables
2100 must either be lexically scoped (using "my"), declared beforehand using
2101 "our", or explicitly qualified to say which package the global variable
2104 =item Hexadecimal number > 0xffffffff non-portable
2106 (W) The hexadecimal number you specified is larger than 2**32-1
2107 (4294967295) and therefore non-portable between systems. See
2108 L<perlport> for more on portability concerns.
2110 =item Ill-formed CRTL environ value "%s"
2112 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2113 environ array, and encountered an element without the C<=> delimiter
2114 used to spearate keys from values. The element is ignored.
2116 =item Ill-formed message in prime_env_iter: |%s|
2118 (W) A warning peculiar to VMS. Perl tried to read a logical name
2119 or CLI symbol definition when preparing to iterate over %ENV, and
2120 didn't see the expected delimiter between key and value, so the
2123 =item Illegal binary digit %s
2125 (F) You used a digit other than 0 or 1 in a binary number.
2127 =item Illegal binary digit %s ignored
2129 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2130 Interpretation of the binary number stopped before the offending digit.
2132 =item Illegal number of bits in vec
2134 (F) The number of bits in vec() (the third argument) must be a power of
2135 two from 1 to 32 (or 64, if your platform supports that).
2137 =item Integer overflow in %s number
2139 (W) The hexadecimal, octal or binary number you have specified either
2140 as a literal or as an argument to hex() or oct() is too big for your
2141 architecture, and has been converted to a floating point number. On a
2142 32-bit architecture the largest hexadecimal, octal or binary number
2143 representable without overflow is 0xFFFFFFFF, 037777777777, or
2144 0b11111111111111111111111111111111 respectively. Note that Perl
2145 transparently promotes all numbers to a floating point representation
2146 internally--subject to loss of precision errors in subsequent
2149 =item Invalid %s attribute: %s
2151 The indicated attribute for a subroutine or variable was not recognized
2152 by Perl or by a user-supplied handler. See L<attributes>.
2154 =item Invalid %s attributes: %s
2156 The indicated attributes for a subroutine or variable were not recognized
2157 by Perl or by a user-supplied handler. See L<attributes>.
2159 =item invalid [] range "%s" in regexp
2161 The offending range is now explicitly displayed.
2163 =item Invalid separator character %s in attribute list
2165 (F) Something other than a colon or whitespace was seen between the
2166 elements of an attribute list. If the previous attribute
2167 had a parenthesised parameter list, perhaps that list was terminated
2168 too soon. See L<attributes>.
2170 =item Invalid separator character %s in subroutine attribute list
2172 (F) Something other than a colon or whitespace was seen between the
2173 elements of a subroutine attribute list. If the previous attribute
2174 had a parenthesised parameter list, perhaps that list was terminated
2177 =item leaving effective %s failed
2179 (F) While under the C<use filetest> pragma, switching the real and
2180 effective uids or gids failed.
2182 =item Lvalue subs returning %s not implemented yet
2184 (F) Due to limitations in the current implementation, array and hash
2185 values cannot be returned in subroutines used in lvalue context.
2186 See L<perlsub/"Lvalue subroutines">.
2188 =item Method %s not permitted
2192 =item Missing %sbrace%s on \N{}
2194 (F) Wrong syntax of character name literal C<\N{charname}> within
2195 double-quotish context.
2197 =item Missing command in piped open
2199 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2200 construction, but the command was missing or blank.
2202 =item Missing name in "my sub"
2204 (F) The reserved syntax for lexically scoped subroutines requires that they
2205 have a name with which they can be found.
2207 =item No %s specified for -%c
2209 (F) The indicated command line switch needs a mandatory argument, but
2210 you haven't specified one.
2212 =item No package name allowed for variable %s in "our"
2214 (F) Fully qualified variable names are not allowed in "our" declarations,
2215 because that doesn't make much sense under existing semantics. Such
2216 syntax is reserved for future extensions.
2218 =item No space allowed after -%c
2220 (F) The argument to the indicated command line switch must follow immediately
2221 after the switch, without intervening spaces.
2223 =item no UTC offset information; assuming local time is UTC
2225 (S) A warning peculiar to VMS. Perl was unable to find the local
2226 timezone offset, so it's assuming that local system time is equivalent
2227 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2228 to translate to the number of seconds which need to be added to UTC to
2231 =item Octal number > 037777777777 non-portable
2233 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2234 and therefore non-portable between systems. See L<perlport> for more
2235 on portability concerns.
2237 See also L<perlport> for writing portable code.
2239 =item panic: del_backref
2241 (P) Failed an internal consistency check while trying to reset a weak
2244 =item panic: kid popen errno read
2246 (F) forked child returned an incomprehensible message about its errno.
2248 =item panic: magic_killbackrefs
2250 (P) Failed an internal consistency check while trying to reset all weak
2251 references to an object.
2253 =item Parentheses missing around "%s" list
2255 (W) You said something like
2261 my ($foo, $bar) = @_;
2263 Remember that "my", "our" and "local" bind closer than comma.
2265 =item Possible Y2K bug: %s
2267 (W) You are concatenating the number 19 with another number, which
2268 could be a potential Year 2000 problem.
2270 =item Premature end of script headers
2274 =item Repeat count in pack overflows
2276 (F) You can't specify a repeat count so large that it overflows
2277 your signed integers. See L<perlfunc/pack>.
2279 =item Repeat count in unpack overflows
2281 (F) You can't specify a repeat count so large that it overflows
2282 your signed integers. See L<perlfunc/unpack>.
2284 =item realloc() of freed memory ignored
2286 (S) An internal routine called realloc() on something that had already
2289 =item Reference is already weak
2291 (W) You have attempted to weaken a reference that is already weak.
2292 Doing so has no effect.
2294 =item setpgrp can't take arguments
2296 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2297 unlike POSIX setpgid(), which takes a process ID and process group ID.
2299 =item Strange *+?{} on zero-length expression
2301 (W) You applied a regular expression quantifier in a place where it
2302 makes no sense, such as on a zero-width assertion.
2303 Try putting the quantifier inside the assertion instead. For example,
2304 the way to match "abc" provided that it is followed by three
2305 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2307 =item switching effective %s is not implemented
2309 (F) While under the C<use filetest> pragma, we cannot switch the
2310 real and effective uids or gids.
2312 =item This Perl can't reset CRTL environ elements (%s)
2314 =item This Perl can't set CRTL environ elements (%s=%s)
2316 (W) Warnings peculiar to VMS. You tried to change or delete an element
2317 of the CRTL's internal environ array, but your copy of Perl wasn't
2318 built with a CRTL that contained the setenv() function. You'll need to
2319 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2320 L<perlvms>) so that the environ array isn't the target of the change to
2321 %ENV which produced the warning.
2323 =item Unknown open() mode '%s'
2325 (F) The second argument of 3-argument open() is not among the list
2326 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2327 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2329 =item Unknown process %x sent message to prime_env_iter: %s
2331 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2332 iterating over it, and someone else stuck a message in the stream of
2333 data Perl expected. Someone's very confused, or perhaps trying to
2334 subvert Perl's population of %ENV for nefarious purposes.
2336 =item Unrecognized escape \\%c passed through
2338 (W) You used a backslash-character combination which is not recognized
2339 by Perl. The character was understood literally.
2341 =item Unterminated attribute parameter in attribute list
2343 (F) The lexer saw an opening (left) parenthesis character while parsing an
2344 attribute list, but the matching closing (right) parenthesis
2345 character was not found. You may need to add (or remove) a backslash
2346 character to get your parentheses to balance. See L<attributes>.
2348 =item Unterminated attribute list
2350 (F) The lexer found something other than a simple identifier at the start
2351 of an attribute, and it wasn't a semicolon or the start of a
2352 block. Perhaps you terminated the parameter list of the previous attribute
2353 too soon. See L<attributes>.
2355 =item Unterminated attribute parameter in subroutine attribute list
2357 (F) The lexer saw an opening (left) parenthesis character while parsing a
2358 subroutine attribute list, but the matching closing (right) parenthesis
2359 character was not found. You may need to add (or remove) a backslash
2360 character to get your parentheses to balance.
2362 =item Unterminated subroutine attribute list
2364 (F) The lexer found something other than a simple identifier at the start
2365 of a subroutine attribute, and it wasn't a semicolon or the start of a
2366 block. Perhaps you terminated the parameter list of the previous attribute
2369 =item Value of CLI symbol "%s" too long
2371 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2372 element from a CLI symbol table, and found a resultant string longer
2373 than 1024 characters. The return value has been truncated to 1024
2376 =item Version number must be a constant number
2378 (P) The attempt to translate a C<use Module n.n LIST> statement into
2379 its equivalent C<BEGIN> block found an internal inconsistency with
2384 =head1 Obsolete Diagnostics
2388 =item Character class syntax [: :] is reserved for future extensions
2390 (W) Within regular expression character classes ([]) the syntax beginning
2391 with "[:" and ending with ":]" is reserved for future extensions.
2392 If you need to represent those character sequences inside a regular
2393 expression character class, just quote the square brackets with the
2394 backslash: "\[:" and ":\]".
2396 =item Ill-formed logical name |%s| in prime_env_iter
2398 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2399 to iterate over %ENV which violates the syntactic rules governing logical
2400 names. Because it cannot be translated normally, it is skipped, and will not
2401 appear in %ENV. This may be a benign occurrence, as some software packages
2402 might directly modify logical name tables and introduce nonstandard names,
2403 or it may indicate that a logical name table has been corrupted.
2405 =item Probable precedence problem on %s
2407 (W) The compiler found a bareword where it expected a conditional,
2408 which often indicates that an || or && was parsed as part of the
2409 last argument of the previous construct, for example:
2413 =item regexp too big
2415 (F) The current implementation of regular expressions uses shorts as
2416 address offsets within a string. Unfortunately this means that if
2417 the regular expression compiles to longer than 32767, it'll blow up.
2418 Usually when you want a regular expression this big, there is a better
2419 way to do it with multiple statements. See L<perlre>.
2421 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2423 (D) Perl versions before 5.004 misinterpreted any type marker followed
2424 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2425 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2427 However, the developers of Perl 5.004 could not fix this bug completely,
2428 because at least two widely-used modules depend on the old meaning of
2429 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2430 old (broken) way inside strings; but it generates this message as a
2431 warning. And in Perl 5.005, this special treatment will cease.
2437 If you find what you think is a bug, you might check the
2438 articles recently posted to the comp.lang.perl.misc newsgroup.
2439 There may also be information at http://www.perl.com/perl/, the Perl
2442 If you believe you have an unreported bug, please run the B<perlbug>
2443 program included with your release. Make sure to trim your bug down
2444 to a tiny but sufficient test case. Your bug report, along with the
2445 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2446 analysed by the Perl porting team.
2450 The F<Changes> file for exhaustive details on what changed.
2452 The F<INSTALL> file for how to build Perl.
2454 The F<README> file for general stuff.
2456 The F<Artistic> and F<Copying> files for copyright information.
2460 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2461 contributions from The Perl Porters.
2463 Send omissions or corrections to <F<perlbug@perl.com>>.