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 Literals of the form C<1.2.3> parse differently
89 Previously, numeric literals with more than one dot in them were
90 interpreted as a floating point number concatenated with one or more
91 numbers. Such "numbers" are now parsed as strings composed of the
94 For example, C<print 97.98.99> used to output C<97.9899> in earlier
95 versions, but now prints C<abc>.
97 See L<Support for strings represented as a vector of ordinals> below.
99 =item Possibly changed pseudo-random number generator
101 In 5.005_0x and earlier, perl's rand() function used the C library
102 rand(3) function. As of 5.005_52, Configure tests for drand48(),
103 random(), and rand() (in that order) and picks the first one it finds.
104 Perl programs that depend on reproducing a specific set of pseudo-random
105 numbers will now likely produce different output. You can use
106 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
108 =item Hashing function for hash keys has changed
110 Perl hashes are not order preserving. The apparently random order
111 encountered when iterating on the contents of a hash is determined
112 by the hashing algorithm used. To improve the distribution of lower
113 bits in the hashed value, the algorithm has changed slightly as of
114 5.005_52. When iterating over hashes, this may yield a random order
115 that is B<different> from that of previous versions.
117 =item C<undef> fails on read only values
119 Using the C<undef> operator on a readonly value (such as $1) has
120 the same effect as assigning C<undef> to the readonly value--it
123 =item Close-on-exec bit may be set on pipe and socket handles
125 On systems that support a close-on-exec flag on filehandles, the
126 flag will be set for any handles created by pipe(), socketpair(),
127 socket(), and accept(), if that is warranted by the value of $^F
128 that may be in effect. Earlier versions neglected to set the flag
129 for handles created with these operators. See L<perlfunc/pipe>,
130 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
133 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
135 Perl 5.004 deprecated the interpretation of C<$$1> and
136 similar within interpolated strings to mean C<$$ . "1">,
137 but still allowed it.
139 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
141 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
143 delete(), each(), values() and hashes in a list context return the actual
144 values in the hash, instead of copies (as they used to in earlier
145 versions). Typical idioms for using these constructs copy the
146 returned values, but this can make a significant difference when
147 creating references to the returned values.
149 Keys in the hash are still returned as copies when iterating on
152 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
154 vec() generates a run-time error if the BITS argument is not
155 a valid power-of-two integer.
157 =item Text of some diagnostic output has changed
159 Most references to internal Perl operations in diagnostics
160 have been changed to be more descriptive. This may be an
161 issue for programs that may incorrectly rely on the exact
162 text of diagnostics for proper functioning.
164 =item C<%@> has been removed
166 The undocumented special variable C<%@> that used to accumulate
167 "background" errors (such as those that happen in DESTROY())
168 has been removed, because it could potentially result in memory
171 =item Parenthesized not() behaves like a list operator
173 The C<not> operator now falls under the "if it looks like a function,
174 it behaves like a function" rule.
176 As a result, the parenthesized form can be used with C<grep> and C<map>.
177 The following construct used to be a syntax error before, but it works
180 grep not($_), @things;
182 On the other hand, using C<not> with a literal list slice may not
183 work. The following previously allowed construct:
185 print not (1,2,3)[0];
187 needs to be written with additional parentheses now:
189 print not((1,2,3)[0]);
191 The behavior remains unaffected when C<not> is not followed by parentheses.
193 =item Semantics of bareword prototype C<(*)> have changed
195 Arguments prototyped as C<*> will now be visible within the subroutine
196 as either a simple scalar or as a reference to a typeglob. Perl 5.005
197 always coerced simple scalar arguments to a typeglob, which wasn't useful
198 in situations where the subroutine must distinguish between a simple
199 scalar and a typeglob. See L<perlsub/Prototypes>.
203 =head2 C Source Incompatibilities
207 =item C<PERL_POLLUTE>
209 Release 5.005 grandfathered old global symbol names by providing preprocessor
210 macros for extension source compatibility. As of release 5.6, these
211 preprocessor definitions are not available by default. You need to explicitly
212 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
213 extensions still using the old symbols, this option can be
214 specified via MakeMaker:
216 perl Makefile.PL POLLUTE=1
218 =item C<PERL_IMPLICIT_CONTEXT>
220 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
221 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
222 intended to be enabled by users at this time.
224 This new build option provides a set of macros for all API functions
225 such that an implicit interpreter/thread context argument is passed to
226 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
227 amounts to a macro invocation that actually translates to something like
228 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
229 to not have any significant source compatibility issues, the difference
230 between a macro and a real function call will need to be considered.
232 This means that there B<is> a source compatibility issue as a result of
233 this if your extensions attempt to use pointers to any of the Perl API
236 Note that the above issue is not relevant to the default build of
237 Perl, whose interfaces continue to match those of prior versions
238 (but subject to the other options described here).
240 See L<perlguts/"The Perl API"> for detailed information on the
241 ramifications of building Perl using this option.
243 =item C<PERL_POLLUTE_MALLOC>
245 Enabling Perl's malloc in release 5.005 and earlier caused
246 the namespace of system versions of the malloc family of functions to
247 be usurped by the Perl versions, since by default they used the
250 Besides causing problems on platforms that do not allow these functions to
251 be cleanly replaced, this also meant that the system versions could not
252 be called in programs that used Perl's malloc. Previous versions of Perl
253 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
254 EMBEDMYMALLOC preprocessor definitions.
256 As of release 5.6, Perl's malloc family of functions have default names
257 distinct from the system versions. You need to explicitly compile perl with
258 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
259 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
262 Note that these functions do B<not> constitute Perl's memory allocation API.
263 See L<perlguts/"Memory Allocation"> for further information about that.
267 =head2 Compatible C Source API Changes
271 =item C<PATCHLEVEL> is now C<PERL_VERSION>
273 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
274 are now available by default from perl.h, and reflect the base revision,
275 patchlevel, and subversion respectively. C<PERL_REVISION> had no
276 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
277 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
279 The new names cause less pollution of the B<cpp> namespace and reflect what
280 the numbers have come to stand for in common practice. For compatibility,
281 the old names are still supported when F<patchlevel.h> is explicitly
282 included (as required before), so there is no source incompatibility
285 =item Support for C++ exceptions
287 change#3386, also needs perlguts documentation
288 [TODO - Chip Salzenberg <chip@perlsupport.com>]
292 =head2 Binary Incompatibilities
294 In general, the default build of this release is expected to be binary
295 compatible for extensions built with the 5.005 release or its maintenance
296 versions. However, specific platforms may have broken binary compatibility
297 due to changes in the defaults used in hints files. Therefore, please be
298 sure to always check the platform-specific README files for any notes to
301 The usethreads or usemultiplicity builds are B<not> binary compatible
302 with the corresponding builds in 5.005.
304 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
305 among others), purely internal symbols such as parser functions and the
306 run time opcodes are not exported by default. Perl 5.005 used to export
307 all functions irrespective of whether they were considered part of the
310 For the full list of public API functions, see L<perlapi>.
312 =head1 Installation and Configuration Improvements
314 =head2 -Dusethreads means something different
316 WARNING: Support for threads continues to be an experimental feature.
317 Interfaces and implementation are subject to sudden and drastic changes.
319 The -Dusethreads flag now enables the experimental interpreter-based thread
320 support by default. To get the flavor of experimental threads that was in
321 5.005 instead, you need to ask for -Duse5005threads.
323 As of v5.5.640, interpreter-threads support is still lacking a way to
324 create new threads from Perl (i.e., C<use Thread;> will not work with
325 interpreter threads). C<use Thread;> continues to be available when you
326 ask for -Duse5005threads, bugs and all.
328 =head2 New Configure flags
330 The following new flags may be enabled on the Configure command line
331 by running Configure with C<-Dflag>.
340 =head2 -Dusethreads and -Duse64bits now more daring
342 The Configure options enabling the use of threads and the use of
343 64-bitness are now more daring in the sense that they no more have an
344 explicit list of operating systems of known threads/64-bit
345 capabilities. In other words: if your operating system has the
346 necessary APIs and datatypes, you should be able just to go ahead and
347 use them, for threads by Configure -Dusethreads, and for 64 bits
348 either explicitly by Configure -Duse64bits or implicitly if your
349 system has 64 bit wide datatypes. See also L<"64-bit support">.
353 Some platforms have "long doubles", floating point numbers of even
354 larger range than ordinary "doubles". To enable using long doubles for
355 Perl's scalars, use -Duselongdouble.
359 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
360 See also L<"64-bit support">.
362 =head2 -Duselargefiles
364 Some platforms support large files, files larger than two gigabytes.
365 See L<"Large file support"> for more information.
367 =head2 installusrbinperl
369 You can use "Configure -Uinstallusrbinperl" which causes installperl
370 to skip installing perl also as /usr/bin/perl. This is useful if you
371 prefer not to modify /usr/bin for some reason or another but harmful
372 because many scripts assume to find Perl in /usr/bin/perl.
376 You can use "Configure -Dusesocks" which causes Perl to probe
377 for the SOCKS (v5, not v4) proxy protocol library,
378 http://www.socks.nec.com/
382 You can "post-edit" the Configure variables using the Configure C<-A>
383 flag. The editing happens immediately after the platform specific
384 hints files have been processed but before the actual configuration
385 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
387 =head2 Enhanced Installation Directories
389 The installation structure has been enriched to improve the support
390 for maintaining multiple versions of perl, to provide locations for
391 vendor-supplied modules, scripts, and manpages, and to ease maintenance
392 of locally-added modules, scripts, and manpages. See the section on
393 Installation Directories in the INSTALL file for complete details.
394 For most users building and installing from source, the defaults should
397 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
398 special values for library directories, you might wish to consider using
399 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
400 config.sh file from an earlier version of perl, you should be sure to
401 check that Configure makes sensible choices for the new directories.
402 See INSTALL for complete details.
406 =head2 Unicode and UTF-8 support
408 Perl can optionally use UTF-8 as its internal representation for character
409 strings. The C<utf8> and C<bytes> pragmas are used to control this support
410 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
413 =head2 Interpreter cloning, threads, and concurrency
415 WARNING: This is an experimental feature in a pre-alpha state. Use
418 Perl 5.005_63 introduces the beginnings of support for running multiple
419 interpreters concurrently in different threads. In conjunction with
420 the perl_clone() API call, which can be used to selectively duplicate
421 the state of any given interpreter, it is possible to compile a
422 piece of code once in an interpreter, clone that interpreter
423 one or more times, and run all the resulting interpreters in distinct
426 On Windows, this feature is used to emulate fork() at the interpreter
427 level. See L<perlfork>.
429 This feature is still in evolution. It is eventually meant to be used
430 to selectively clone a subroutine and data reachable from that
431 subroutine in a separate interpreter and run the cloned subroutine
432 in a separate thread. Since there is no shared data between the
433 interpreters, little or no locking will be needed (unless parts of
434 the symbol table are explicitly shared). This is obviously intended
435 to be an easy-to-use replacement for the existing threads support.
437 Support for cloning interpreters and interpreter concurrency can be
438 enabled using the -Dusethreads Configure option (see win32/Makefile for
439 how to enable it on Windows.) The resulting perl executable will be
440 functionally identical to one that was built with -Dmultiplicity, but
441 the perl_clone() API call will only be available in the former.
443 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
444 Perl source code changes that provide a clear separation between the op tree
445 and the data it operates with. The former is considered immutable, and can
446 therefore be shared between an interpreter and all of its clones, while the
447 latter is considered local to each interpreter, and is therefore copied for
450 Note that building Perl with the -Dusemultiplicity Configure option
451 is adequate if you wish to run multiple B<independent> interpreters
452 concurrently in different threads. -Dusethreads only provides the
453 additional functionality of the perl_clone() API call and other
454 support for running B<cloned> interpreters concurrently.
456 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
459 =head2 Lexically scoped warning categories
461 You can now control the granularity of warnings emitted by perl at a finer
462 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
465 =head2 Lvalue subroutines
467 WARNING: This is an experimental feature.
470 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
471 Tuomas Lukka <lukka@iki.fi>)]
473 =head2 "our" declarations
475 An "our" declaration introduces a value that can be best understood
476 as a lexically scoped symbolic alias to a global variable in the
477 package that was current where the variable was declared. This is
478 mostly useful as an alternative to the C<vars> pragma, but also provides
479 the opportunity to introduce typing and other attributes for such
480 variables. See L<perlfunc/our>.
482 =head2 Support for strings represented as a vector of ordinals
484 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
485 of characters with the specified ordinals. This is an alternative, more
486 readable way to construct (possibly unicode) strings instead of
487 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
488 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
489 parsed the same as C<v1.2.3>.
491 Strings written in this form are also useful to represent version "numbers".
492 It is easy to compare such version "numbers" (which are really just plain
493 strings) using any of the usual string comparison operators C<eq>, C<ne>,
494 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
497 In conjunction with the new C<$^V> magic variable (which contains
498 the perl version as a string), such literals can be used as a readable way
499 to check if you're running a particular version of Perl:
501 # this will parse in older versions of Perl also
502 if ($^V and $^V gt v5.5.640) {
503 # new features supported
506 C<require> and C<use> also have some special magic to support such literals.
507 They will be interpreted as a version rather than as a module name:
509 require v5.6.0; # croak if $^V lt v5.6.0
510 use v5.6.0; # same, but croaks at compile-time
512 Alternatively, the C<v> may be omitted if there is more than one dot:
517 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
518 to print ordinals of characters in arbitrary strings:
520 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
521 printf "%*vX", ":", $addr; # formats IPv6 address
522 printf "%*vb", " ", $bits; # displays bitstring
524 See L<perlop/"Strings of Character"> for additional information.
526 =head2 Weak references
528 WARNING: This is an experimental feature.
530 In previous versions of Perl, you couldn't cache objects so as
531 to allow them to be deleted if the last reference from outside
532 the cache is deleted. The reference in the cache would hold a
533 reference count on the object and the objects would never be
536 Another familiar problem is with circular references. When an
537 object references itself, its reference count would never go
538 down to zero, and it would not get destroyed until the program
541 Weak references solve this by allowing you to "weaken" any
542 reference, that is, make it not count towards the reference count.
543 When the last non-weak reference to an object is deleted, the object
544 is destroyed and all the weak references to the object are
545 automatically undef-ed.
547 To use this feature, you need the WeakRef package from CPAN, which
548 contains additional documentation.
550 change#3385, also need perlguts documentation
551 [TODO - Tuomas Lukka <lukka@iki.fi>]
553 =head2 File globbing implemented internally
555 WARNING: This is currently an experimental feature. Interfaces and
556 implementation are likely to change.
558 Perl now uses the File::Glob implementation of the glob() operator
559 automatically. This avoids using an external csh process and the
560 problems associated with it.
562 =head2 Binary numbers supported
564 Binary numbers are now supported as literals, in s?printf formats, and
568 printf "The answer is: %b\n", oct("0b101010");
570 =head2 Some arrows may be omitted in calls through references
572 Perl now allows the arrow to be omitted in many constructs
573 involving subroutine calls through references. For example,
574 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
575 This is rather similar to how the arrow may be omitted from
576 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
577 required for C<foo(10)-E<gt>('bar')>.
579 =head2 exists() is supported on subroutine names
581 The exists() builtin now works on subroutine names. A subroutine
582 is considered to exist if it has been declared (even if implicitly).
583 See L<perlfunc/exists> for examples.
585 =head2 exists() and delete() are supported on array elements
587 The exists() and delete() builtins now work on simple arrays as well.
588 The behavior is similar to that on hash elements.
590 exists() can be used to check whether an array element has been
591 initialized. This avoids autovivifying array elements that don't exist.
592 If the array is tied, the EXISTS() method in the corresponding tied
593 package will be invoked.
595 delete() may be used to remove an element from the array and return
596 it. The array element at that position returns to its unintialized
597 state, so that testing for the same element with exists() will return
598 false. If the element happens to be the one at the end, the size of
599 the array also shrinks up to the highest element that tests true for
600 exists(), or 0 if none such is found. If the array is tied, the DELETE()
601 method in the corresponding tied package will be invoked.
603 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
605 =head2 syswrite() ease-of-use
607 The length argument of C<syswrite()> has become optional.
609 =head2 File and directory handles can be autovivified
611 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
612 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
613 socket(), and accept()) now autovivify a file or directory handle
614 if the handle passed to them is an uninitialized scalar variable. This
615 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
616 to be used to create filehandles that will conveniently be closed
617 automatically when the scope ends, provided there are no other references
618 to them. This largely eliminates the need for typeglobs when opening
619 filehandles that must be passed around, as in the following example:
623 or die "Can't open '@_': $!";
628 my $f = myopen("</etc/motd");
630 # $f implicitly closed here
633 [TODO - this idiom needs more pod penetration]
635 =head2 64-bit support
637 All platforms that have 64-bit integers either (a) natively as longs
638 or ints (b) via special compiler flags (c) using long long are able to
639 use "quads" (64-integers) as follows:
645 constants (decimal, hexadecimal, octal, binary) in the code
649 arguments to oct() and hex()
653 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
661 pack() and unpack() "q" and "Q" formats
665 in basic arithmetics: + - * / %
669 vec() (but see the below note about bit arithmetics)
673 Note that unless you have the case (a) you will have to configure
674 and compile Perl using the -Duse64bits Configure flag.
676 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
677 64-bit clean, they are explictly forced to be 32-bit because of
678 tangled backward compatibility issues. This limitation is subject to
679 change. Bit arithmetics for bit vector scalars (created by vec()) are
680 not limited in their width, you can use the & | ^ ~ operators on such
683 There are actually two modes of 64-bitness: the first one is achieved
684 using Configure -Duse64bits and the second one using Configure
685 -Dusefull64bits. The difference is that the first one is minimal and
686 the second one maximal. The first one does only as much as is
687 required to get 64-bit integers into Perl (this may mean, for example,
688 using "long longs") while your memory may still be limited to 2
689 gigabytes (because your pointers most likely are 32-bit); the second
690 one goes all the way by attempting to switch also longs (and pointers)
691 being 64-bit. This may create an even more binary incompatible Perl
692 than -Duse64bits: the resulting executable may not run at all in a
693 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
694 operating system to be 64-bit aware.
696 Natively 64-bit systems like Alpha and Cray need neither -Duse64bits
699 Last but not least: note that due to Perl's habit of always using
700 floating point numbers the quads are still not true integers.
701 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
702 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
703 are silently promoted to floating point numbers, after which they will
704 start losing precision (their lower digits).
706 =head2 Large file support
708 If you have filesystems that support "large files" (files larger than
709 2 gigabytes), you may now also be able to create and access them from
710 Perl. You have to use Configure -Duselargefiles. Turning on the
711 large file support turns on also the 64-bit support on many platforms.
712 Beware that unless your filesystem also supports "sparse files" seeking
713 to umpteen petabytes may be unadvisable.
715 Note that in addition to requiring a proper file system to do large
716 files you may also need to adjust your per-process (or your
717 per-system, or per-process-group, or per-user-group) maximum filesize
718 limits before running Perl scripts that try to handle large files,
719 especially if you intend to write such files.
721 Finally, in addition to your process/process group maximum filesize
722 limits, you may have quota limits on your filesystems that stop you
723 (your user id or your user group id) from using large files.
725 Adjusting your process/user/group/file system/operating system limits
726 is outside the scope of Perl core language. For process limits, you
727 may try increasing the limits using your shell's limits/limit/ulimit
728 command before running Perl. The BSD::Resource extension (not
729 included with the standard Perl distribution) may also be of use, it
730 offers the getrlimit/setrlimit interface that can be used to adjust
731 process resource usage limits, including the maximum filesize limit.
735 In some systems you may be able to use long doubles to enhance the
736 range and precision of your double precision floating point numbers
737 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
738 this support (if it is available).
742 You can "Configure -Dusemorebits" to turn on both the 64-bit support
743 and the long double support.
745 =head2 Enhanced support for sort() subroutines
747 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
748 now be used as sort subroutines. In either case, the two elements to
749 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
751 For unprototyped sort subroutines, the historical behavior of passing
752 the elements to be compared as the global variables $a and $b remains
755 =head2 Better syntax checks on parenthesized unary operators
759 print defined(&foo,&bar,&baz);
760 print uc("foo","bar","baz");
763 used to be accidentally allowed in earlier versions, and produced
764 unpredictable behaviour. Some produced ancillary warnings
765 when used in this way; others silently did the wrong thing.
767 The parenthesized forms of most unary operators that expect a single
768 argument now ensure that they are not called with more than one
769 argument, making the cases shown above syntax errors. The usual
772 print defined &foo, &bar, &baz;
773 print uc "foo", "bar", "baz";
776 remains unchanged. See L<perlop>.
778 =head2 POSIX character class syntax [: :] supported
780 For example to match alphabetic characters use /[[:alpha:]]/.
781 See L<perlre> for details.
783 =head2 Improved C<qw//> operator
785 The C<qw//> operator is now evaluated at compile time into a true list
786 instead of being replaced with a run time call to C<split()>. This
787 removes the confusing misbehaviour of C<qw//> in scalar context, which
788 had inherited that behaviour from split().
792 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
794 now correctly prints "3|a", instead of "2|a".
796 =head2 pack() format 'Z' supported
798 The new format type 'Z' is useful for packing and unpacking null-terminated
799 strings. See L<perlfunc/"pack">.
801 =head2 pack() format modifier '!' supported
803 The new format type modifier '!' is useful for packing and unpacking
804 native shorts, ints, and longs. See L<perlfunc/"pack">.
806 =head2 pack() and unpack() support counted strings
808 The template character '/' can be used to specify a counted string
809 type to be packed or unpacked. See L<perlfunc/"pack">.
811 =head2 Comments in pack() templates
813 The '#' character in a template introduces a comment up to
814 end of the line. This facilitates documentation of pack()
817 =head2 $^X variables may now have names longer than one character
819 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
820 error. Now variable names that begin with a control character may be
821 arbitrarily long. However, for compatibility reasons, these variables
822 I<must> be written with explicit braces, as C<${^XY}> for example.
823 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
824 than one control character, such as C<${^XY^Z}>, are illegal.
826 The old syntax has not changed. As before, `^X' may be either a
827 literal control-X character or the two-character sequence `caret' plus
828 `X'. When braces are omitted, the variable name stops after the
829 control character. Thus C<"$^XYZ"> continues to be synonymous with
830 C<$^X . "YZ"> as before.
832 As before, lexical variables may not have names beginning with control
833 characters. As before, variables whose names begin with a control
834 character are always forced to be in package `main'. All such variables
835 are reserved for future extensions, except those that begin with
836 C<^_>, which may be used by user programs and are guaranteed not to
837 acquire special meaning in any future version of Perl.
839 =head2 C<use attrs> implicit in subroutine attributes
841 Formerly, if you wanted to mark a subroutine as being a method call or
842 as requiring an automatic lock() when it is entered, you had to declare
843 that with a C<use attrs> pragma in the body of the subroutine.
844 That can now be accomplished with declaration syntax, like this:
846 sub mymethod : locked method ;
848 sub mymethod : locked method {
852 sub othermethod :locked :method ;
854 sub othermethod :locked :method {
859 (Note how only the first C<:> is mandatory, and whitespace surrounding
860 the C<:> is optional.)
862 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
863 with the stubs they provide. See L<attributes>.
865 =head2 Regular expression improvements
867 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
868 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
870 =head2 Overloading improvements
873 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
875 =head2 open() with more than two arguments
877 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
879 =head2 Support for interpolating named characters
882 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
884 =head2 Experimental support for user-hooks in @INC
886 [TODO - Ken Fox <kfox@ford.com>]
888 =head2 C<require> and C<do> may be overridden
890 C<require> and C<do 'file'> operations may be overridden locally
891 by importing subroutines of the same name into the current package
892 (or globally by importing them into the CORE::GLOBAL:: namespace).
893 Overriding C<require> will also affect C<use>, provided the override
894 is visible at compile-time.
895 See L<perlsub/"Overriding Built-in Functions">.
897 =head2 New variable $^C reflects C<-c> switch
899 C<$^C> has a boolean value that reflects whether perl is being run
900 in compile-only mode (i.e. via the C<-c> switch). Since
901 BEGIN blocks are executed under such conditions, this variable
902 enables perl code to determine whether actions that make sense
903 only during normal running are warranted. See L<perlvar>.
905 =head2 New variable $^V contains Perl version in v5.6.0 format
907 C<$^V> contains the Perl version number as a string composed of
908 characters whose ordinals match the version numbers, so that it may
909 be used in string comparisons.
911 See C<Support for strings represented as a vector of ordinals> for an
914 =head2 Optional Y2K warnings
916 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
917 it emits optional warnings when concatenating the number 19
920 This behavior must be specifically enabled when running Configure.
921 See F<INSTALL> and F<README.Y2K>.
923 =head1 Significant bug fixes
925 =head2 E<lt>HANDLEE<gt> on empty files
927 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
928 zero length (instead of C<undef>, as it used to) the first time the
929 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
932 This means that the following will append "foo" to an empty file (it used
935 perl -0777 -pi -e 's/^/foo/' empty_file
939 perl -pi -e 's/^/foo/' empty_file
941 is unchanged (it continues to leave the file empty).
943 =head2 C<eval '...'> improvements
945 Line numbers (as reflected by caller() and most diagnostics) within
946 C<eval '...'> were often incorrect when here documents were involved.
947 This has been corrected.
949 Lexical lookups for variables appearing in C<eval '...'> within
950 functions that were themselves called within an C<eval '...'> were
951 searching the wrong place for lexicals. The lexical search now
952 correctly ends at the subroutine's block boundary.
954 Parsing of here documents used to be flawed when they appeared as
955 the replacement expression in C<eval 's/.../.../e'>. This has
958 =head2 All compilation errors are true errors
960 Some "errors" encountered at compile time were by neccessity
961 generated as warnings followed by eventual termination of the
962 program. This enabled more such errors to be reported in a
963 single run, rather than causing a hard stop at the first error
964 that was encountered.
966 The mechanism for reporting such errors has been reimplemented
967 to queue compile-time errors and report them at the end of the
968 compilation as true errors rather than as warnings. This fixes
969 cases where error messages leaked through in the form of warnings
970 when code was compiled at run time using C<eval STRING>, and
971 also allows such errors to be reliably trapped using __DIE__ hooks.
973 =head2 Automatic flushing of output buffers
975 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
976 of all files opened for output when the operation
977 was attempted. This mostly eliminates confusing
978 buffering mishaps suffered by users unaware of how Perl internally
981 =head2 Better diagnostics on meaningless filehandle operations
983 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
984 are compile time errors. Attempting to read from filehandles that
985 were opened only for writing will now produce warnings (just as
986 writing to read-only filehandles does).
988 =head2 Where possible, buffered data discarded from duped input filehandle
990 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
991 was previously read and buffered in C<OLD> before duping the handle.
992 On platforms where doing this is allowed, the next read operation
993 on C<NEW> will return the same data as the corresponding operation
994 on C<OLD>. Formerly, it would have returned the data from the start
995 of the following disk block instead.
997 =head2 eof() has the same old magic as <>
999 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
1000 yet been made. C<eof()> has been changed to have a little magic of its
1001 own, it now opens the C<E<lt>E<gt>> files.
1003 =head2 system(), backticks and pipe open now reflect exec() failure
1005 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1006 etc., are implemented via fork() and exec(). When the underlying
1007 exec() fails, earlier versions did not report the error properly,
1008 since the exec() happened to be in a different process.
1010 The child process now communicates with the parent about the
1011 error in launching the external command, which allows these
1012 constructs to return with their usual error value and set $!.
1014 =head2 Implicitly closed filehandles are safer
1016 Sometimes implicitly closed filehandles (as when they are localized,
1017 and Perl automatically closes them on exiting the scope) could
1018 inadvertently set $? or $!. This has been corrected.
1020 =head2 C<(\$)> prototype and C<$foo{a}>
1022 An scalar reference prototype now correctly allows a hash or
1023 array element in that slot.
1025 =head2 Pseudo-hashes work better
1027 Dereferencing some types of reference values in a pseudo-hash,
1028 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
1031 When applied to a pseudo-hash element, exists() now reports whether
1032 the specified value exists, not merely if the key is valid.
1034 delete() now works on pseudo-hashes. When given a pseudo-hash element
1035 or slice it deletes the values corresponding to the keys (but not the keys
1036 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1038 =head2 C<goto &sub> and AUTOLOAD
1040 The C<goto &sub> construct works correctly when C<&sub> happens
1043 =head2 C<-bareword> allowed under C<use integer>
1045 The autoquoting of barewords preceded by C<-> did not work
1046 in prior versions when the C<integer> pragma was enabled.
1047 This has been fixed.
1049 =head2 Boolean assignment operators are legal lvalues
1051 Constructs such as C<($a ||= 2) += 1> are now allowed.
1053 =head2 C<sort $coderef @foo> allowed
1055 sort() did not accept a subroutine reference as the comparison
1056 function in earlier versions. This is now permitted.
1058 =head2 Failures in DESTROY()
1060 When code in a destructor threw an exception, it went unnoticed
1061 in earlier versions of Perl, unless someone happened to be
1062 looking in $@ just after the point the destructor happened to
1063 run. Such failures are now visible as warnings when warnings are
1066 =head2 Locale bugs fixed
1068 printf() and sprintf() previously reset the numeric locale
1069 back to the default "C" locale. This has been fixed.
1071 Numbers formatted according to the local numeric locale
1072 (such as using a decimal comma instead of a decimal dot) caused
1073 "isn't numeric" warnings, even while the operations accessing
1074 those numbers produced correct results. The warnings are gone.
1078 The C<eval 'return sub {...}'> construct could sometimes leak
1079 memory. This has been fixed.
1081 Operations that aren't filehandle constructors used to leak memory
1082 when used on invalid filehandles. This has been fixed.
1084 Constructs that modified C<@_> could fail to deallocate values
1085 in C<@_> and thus leak memory. This has been corrected.
1087 =head2 Spurious subroutine stubs after failed subroutine calls
1089 Perl could sometimes create empty subroutine stubs when a
1090 subroutine was not found in the package. Such cases stopped
1091 later method lookups from progressing into base packages.
1092 This has been corrected.
1094 =head2 Consistent numeric conversions
1097 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1099 =head2 Taint failures under C<-U>
1101 When running in unsafe mode, taint violations could sometimes
1102 cause silent failures. This has been fixed.
1104 =head2 END blocks and the C<-c> switch
1106 Prior versions used to run BEGIN B<and> END blocks when Perl was
1107 run in compile-only mode. Since this is typically not the expected
1108 behavior, END blocks are not executed anymore when the C<-c> switch
1111 See L<CHECK blocks> for how to run things when the compile phase ends.
1113 =head2 Potential to leak DATA filehandles
1115 Using the C<__DATA__> token creates an implicit filehandle to
1116 the file that contains the token. It is the program's
1117 responsibility to close it when it is done reading from it.
1119 This caveat is now better explained in the documentation.
1122 =head2 Diagnostics follow STDERR
1124 Diagnostic output now goes to whichever file the C<STDERR> handle
1125 is pointing at, instead of always going to the underlying C runtime
1126 library's C<stderr>.
1128 =head2 Other fixes for better diagnostics
1130 Line numbers are no longer suppressed (under most likely circumstances)
1131 during the global destruction phase.
1133 Diagnostics emitted from code running in threads other than the main
1134 thread are now accompanied by the thread ID.
1136 Embedded null characters in diagnostics now actually show up. They
1137 used to truncate the message in prior versions.
1139 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1140 if sort() is encountered in package foo.
1142 Unrecognized alphabetic escapes encountered when parsing quote
1143 constructs now generate a warning, since they may take on new
1144 semantics in later versions of Perl.
1146 =head1 Performance enhancements
1148 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1150 Many common sort() operations using a simple inlined block are now
1151 optimized for faster performance.
1153 =head2 Optimized assignments to lexical variables
1155 Certain operations in the RHS of assignment statements have been
1156 optimized to directly set the lexical variable on the LHS,
1157 eliminating redundant copying overheads.
1159 =head2 Method lookups optimized
1161 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1163 =head2 Faster mechanism to invoke XSUBs
1166 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1168 =head2 Perl_malloc() improvements
1171 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1173 =head2 Faster subroutine calls
1175 Minor changes in how subroutine calls are handled internally
1176 provide marginal improvements in performance.
1178 =head1 Platform specific changes
1180 =head2 Additional supported platforms
1186 VM/ESA is now supported.
1190 Siemens BS2000 is now supported under the POSIX Shell.
1194 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1199 GNU/Hurd is now supported.
1203 Rhapsody is now supported.
1207 EPOC is is now supported (on Psion 5).
1217 Perl now works with djgpp 2.02 (and 2.03 alpha).
1221 Environment variable names are not converted to uppercase any more.
1225 Wrong exit code from backticks now fixed.
1229 This port is still using its own builtin globbing.
1235 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1239 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1243 Site library searches failed to look for ".../site/5.XXX/lib"
1244 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1246 When given a pathname that consists only of a drivename, such
1247 as C<A:>, opendir() and stat() now use the current working
1248 directory for the drive rather than the drive root.
1250 The builtin XSUB functions in the Win32:: namespace are
1251 documented. See L<Win32>.
1253 $^X now contains the full path name of the running executable.
1255 A Win32::GetLongPathName() function is provided to complement
1256 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1258 POSIX::uname() is supported.
1260 system(1,...) now returns true process IDs rather than process
1261 handles. kill() accepts any real process id, rather than strictly
1262 return values from system(1,...).
1264 The C<Shell> module is supported.
1266 Rudimentary support for building under command.com in Windows 95
1269 Scripts are read in binary mode by default to allow ByteLoader (and
1270 the filter mechanism in general) to work properly. For compatibility,
1271 the DATA filehandle will be set to text mode if a carriage return is
1272 detected at the end of the line containing the __END__ or __DATA__
1273 token; if not, the DATA filehandle will be left open in binary mode.
1274 Earlier versions always opened the DATA filehandle in text mode.
1276 The glob() operator is implemented via the L<File::Glob> extension,
1277 which supports glob syntax of the C shell. This increases the flexibility
1278 of the glob() operator, but there may be compatibility issues for
1279 programs that relied on the older globbing syntax. If you want to
1280 preserve compatibility with the older syntax, you might want to put
1281 a C<use File::DosGlob;> in your program. For details and compatibility
1282 information, see L<File::Glob>.
1292 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1296 IO constants (SEEK_*, _IO*).
1300 Directory-related IO methods (new, read, close, rewind, tied delete).
1302 =item lib/io_multihomed
1304 INET sockets with multi-homed hosts.
1316 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1320 File test operators.
1324 Verify operations that access pad objects (lexicals and temporaries).
1328 Verify C<exists &sub> operations.
1332 =head1 Modules and Pragmata
1340 While used internally by Perl as a pragma, this module also
1341 provides a way to fetch subroutine and variable attributes.
1346 The Perl Compiler suite has been extensively reworked for this
1349 [TODO - Vishal Bhatia <vishal@gol.com>,
1350 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1354 The ByteLoader is a dedicated extension to generate and run
1355 Perl bytecode. See L<ByteLoader>.
1359 References can now be used.
1361 The new version also allows a leading underscore in constant names, but
1362 disallows a double leading underscore (as in "__LINE__"). Some other names
1363 are disallowed or warned against, including BEGIN, END, etc. Some names
1364 which were forced into main:: used to fail silently in some cases; now they're
1365 fatal (outside of main::) and an optional warning (inside of main::).
1366 The ability to detect whether a constant had been set with a given name has
1374 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1378 A C<Maxdepth> setting can be specified to avoid venturing
1379 too deeply into deep data structures. See L<Data::Dumper>.
1381 Dumping C<qr//> objects works correctly.
1385 C<DB> is an experimental module that exposes a clean abstraction
1386 to Perl's debugging API.
1390 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1391 See C<ext/DB_File/Changes>.
1395 Devel::DProf, a Perl source code profiler has been added. See
1396 L<Devel::DProf> and L<dprofpp>.
1400 The Dumpvalue module provides screen dumps of Perl data.
1404 Overall, Benchmark results exhibit lower average error and better timing
1407 You can now run tests for I<n> seconds instead of guessing the right
1408 number of tests to run: e.g. timethese(-5, ...) will run each
1409 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1410 means "for at least 3 CPU seconds". The output format has also
1411 changed. For example:
1413 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1415 will now output something like this:
1417 Benchmark: running a, b, each for at least 5 CPU seconds...
1418 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1419 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1421 New features: "each for at least N CPU seconds...", "wallclock secs",
1422 and the "@ operations/CPU second (n=operations)".
1424 timethese() now returns a reference to a hash of Benchmark objects containing
1425 the test results, keyed on the names of the tests.
1427 timethis() now returns the iterations field in the Benchmark result object
1430 timethese(), timethis(), and the new cmpthese() (see below) can also take
1431 a format specifier of 'none' to suppress output.
1433 A new function countit() is just like timeit() except that it takes a
1434 TIME instead of a COUNT.
1436 A new function cmpthese() prints a chart comparing the results of each test
1437 returned from a timethese() call. For each possible pair of tests, the
1438 percentage speed difference (iters/sec or seconds/iter) is shown.
1440 For other details, see L<Benchmark>.
1444 The Devel::Peek module provides access to the internal representation
1445 of Perl variables and data. It is a data debugging tool for the XS programmer.
1449 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1452 =item ExtUtils::MakeMaker
1454 change#4135, also needs docs in module pod
1455 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1459 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1460 large file (more than 4GB) access Note that the O_LARGEFILE is
1461 automatically/transparently added to sysopen() flags if large file
1462 support has been configured), Free/Net/OpenBSD locking behaviour flags
1463 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1464 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1465 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1466 The chmod()/stat() S_IF* constants and S_IS* functions are available
1467 via the C<:mode> tag.
1472 A compare_text() function has been added, which allows custom
1473 comparison functions. See L<File::Compare>.
1477 File::Find now works correctly when the wanted() function is either
1478 autoloaded or is a symbolic reference.
1480 A bug that caused File::Find to lose track of the working directory
1481 when pruning top-level directories has been fixed.
1483 File::Find now also supports several other options to control its
1484 behavior. It can follow symbolic links if the C<follow> option is
1485 specified. Enabling the C<no_chdir> option will make File::Find skip
1486 changing the current directory when walking directories. The C<untaint>
1487 flag can be useful when running with taint checks enabled.
1493 This extension implements BSD-style file globbing. By default,
1494 it will also be used for the internal implementation of the glob()
1495 operator. See L<File::Glob>.
1499 New methods have been added to the File::Spec module: devnull() returns
1500 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1501 the temp directory (normally /tmp on Unix). There are now also methods
1502 to convert between absolute and relative filenames: abs2rel() and
1503 rel2abs(). For compatibility with operating systems that specify volume
1504 names in file paths, the splitpath(), splitdir(), and catdir() methods
1507 =item File::Spec::Functions
1509 The new File::Spec::Functions modules provides a function interface
1510 to the File::Spec module. Allows shorthand
1512 $fullname = catfile($dir1, $dir2, $file);
1516 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1520 Getopt::Long licensing has changed to allow the Perl Artistic License
1521 as well as the GPL. It used to be GPL only, which got in the way of
1522 non-GPL applications that wanted to use Getopt::Long.
1524 Getopt::Long encourages the use of Pod::Usage to produce help
1525 messages. For example:
1531 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1532 pod2usage(1) if $help;
1533 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1539 sample - Using GetOpt::Long and Pod::Usage
1543 sample [options] [file ...]
1546 -help brief help message
1547 -man full documentation
1555 Print a brief help message and exits.
1559 Prints the manual page and exits.
1565 B<This program> will read the given input file(s) and do someting
1566 useful with the contents thereof.
1570 See L<Pod::Usage> for details.
1572 A bug that prevented the non-option call-back E<lt>E<gt> from being
1573 specified as the first argument has been fixed.
1575 To specify the characters E<lt> and E<gt> as option starters, use
1576 E<gt>E<lt>. Note, however, that changing option starters is strongly
1581 write() and syswrite() will now accept a single-argument
1582 form of the call, for consistency with Perl's syswrite().
1584 You can now create a TCP-based IO::Socket::INET without forcing
1585 a connect attempt. This allows you to configure its options
1586 (like making it non-blocking) and then call connect() manually.
1588 A bug that prevented the IO::Socket::protocol() accessor
1589 from ever returning the correct value has been corrected.
1593 Java Perl Lingo is now distributed with Perl. See jpl/README
1594 for more information.
1598 C<use lib> now weeds out any trailing duplicate entries.
1599 C<no lib> removes all named entries.
1603 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1604 and C<~> are now supported on bigints.
1608 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1609 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1613 A little bit of radial trigonometry (cylindrical and spherical),
1614 radial coordinate conversions, and the great circle distance were added.
1616 =item Pod::Parser, Pod::InputObjects
1618 Pod::Parser is a base class for parsing and selecting sections of
1619 pod documentation from an input stream. This module takes care of
1620 identifying pod paragraphs and commands in the input and hands off the
1621 parsed paragraphs and commands to user-defined methods which are free
1622 to interpret or translate them as they see fit.
1624 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1625 for advanced users of Pod::Parser that need more about a command besides
1628 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1629 "base parser code" recommended for use by all pod2xxx translators.
1630 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1631 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1632 underway. For any questions or comments about pod parsing and translating
1633 issues and utilities, please use the pod-people@perl.org mailing list.
1635 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1637 =item Pod::Checker, podchecker
1639 This utility checks pod files for correct syntax, according to
1640 L<perlpod>. Obvious errors are flagged as such, while warnings are
1641 printed for mistakes that can be handled gracefully. The checklist is
1642 not complete yet. See L<Pod::Checker>.
1644 =item Pod::ParseUtils, Pod::Find
1646 These modules provide a set of gizmos that are useful mainly for pod
1647 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1648 returns found pod files, along with their canonical names (like
1649 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1650 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1651 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1652 (for caching information about pod files, e.g. link nodes).
1654 =item Pod::Select, podselect
1656 Pod::Select is a subclass of Pod::Parser which provides a function
1657 named "podselect()" to filter out user-specified sections of raw pod
1658 documentation from an input stream. podselect is a script that provides
1659 access to Pod::Select from other scripts to be used as a filter.
1662 =item Pod::Usage, pod2usage
1664 Pod::Usage provides the function "pod2usage()" to print usage messages for
1665 a Perl script based on its embedded pod documentation. The pod2usage()
1666 function is generally useful to all script authors since it lets them
1667 write and maintain a single source (the pods) for documentation, thus
1668 removing the need to create and maintain redundant usage message text
1669 consisting of information already in the pods.
1671 There is also a pod2usage script which can be used from other kinds of
1672 scripts to print usage messages from pods (even for non-Perl scripts
1673 with pods embedded in comments).
1675 For details and examples, please see L<Pod::Usage>.
1677 =item Pod::Text and Pod::Man
1679 [TODO - Russ Allbery <rra@stanford.edu>]
1683 An EXISTS method has been added to this module (and sdbm_exists() has
1684 been added to the underlying sdbm library), so one can now call exists
1685 on an SDBM_File tied hash and get the correct result, rather than a
1688 A bug that may have caused data loss when more than one disk block
1689 happens to be read from the database in a single FETCH() has been
1694 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1695 no longer requires syslog.ph to exist.
1699 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1700 uname() if they exist.
1704 The timelocal() and timegm() functions used to silently return bogus
1705 results when the date fell outside the machine's integer range. They
1706 now consistently croak() if the date falls in an unsupported range.
1710 The error return value in list context has been changed for all functions
1711 that return a list of values. Previously these functions returned a list
1712 with a single element C<undef> if an error occurred. Now these functions
1713 return the empty list in these situations. This applies to the following
1719 The remaining functions are unchanged and continue to return C<undef> on
1720 error even in list context.
1722 The Win32::SetLastError(ERROR) function has been added as a complement
1723 to the Win32::GetLastError() function.
1725 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1726 pathname for FILENAME in scalar context. In list context it returns
1727 a two-element list containing the fully qualified directory name and
1728 the filename. See L<Win32>.
1732 A new feature called "DBM Filters" has been added to all the
1733 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1734 DBM Filters add four new methods to each DBM module:
1741 These can be used to filter key-value pairs before the pairs are
1742 written to the database or just after they are read from the database.
1743 See L<perldbmfilter> for further information.
1749 C<use attrs> is now obsolete, and is only provided for
1750 backward-compatibility. It's been replaced by the C<sub : attributes>
1751 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1753 C<use utf8> to enable UTF-8 and Unicode support.
1755 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1758 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1759 ...). Currently only one subpragma implemented, "use filetest
1760 'access';", that uses access(2) or equivalent to check permissions
1761 instead of using stat(2) as usual. This matters in filesystems
1762 where there are ACLs (access control lists): the stat(2) might lie,
1763 but access(2) knows better.
1765 =head1 Utility Changes
1769 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1773 C<perlcc> now supports the C and Bytecode backends. By default,
1774 it generates output from the simple C backend rather than the
1775 optimized C backend.
1777 Support for non-Unix platforms has been improved.
1782 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1784 =head1 Documentation Changes
1790 The official list of public Perl API functions.
1792 =item perlcompile.pod
1794 An introduction to using the Perl Compiler suite.
1796 =item perlfilter.pod
1798 An introduction to writing Perl source filters.
1802 Some guidelines for hacking the Perl source code.
1804 =item perlintern.pod
1806 A list of internal functions in the Perl source code.
1807 (List is currently empty.)
1809 =item perlopentut.pod
1811 A tutorial on using open() effectively.
1813 =item perlreftut.pod
1815 A tutorial that introduces the essentials of references.
1819 A tutorial on managing class data for object modules.
1821 =item perlunicode.pod
1823 An introduction to Unicode support features in Perl.
1827 =head1 New or Changed Diagnostics
1831 =item "%s" variable %s masks earlier declaration in same %s
1833 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1834 effectively eliminating all access to the previous instance. This is almost
1835 always a typographical error. Note that the earlier variable will still exist
1836 until the end of the scope or until all closure referents to it are
1839 =item "my sub" not yet implemented
1841 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1844 =item "our" variable %s redeclared
1846 (W) You seem to have already declared the same global once before in the
1847 current lexical scope.
1849 =item '!' allowed only after types %s
1851 (F) The '!' is allowed in pack() and unpack() only after certain types.
1852 See L<perlfunc/pack>.
1854 =item / cannot take a count
1856 (F) You had an unpack template indicating a counted-length string,
1857 but you have also specified an explicit size for the string.
1858 See L<perlfunc/pack>.
1860 =item / must be followed by a, A or Z
1862 (F) You had an unpack template indicating a counted-length string,
1863 which must be followed by one of the letters a, A or Z
1864 to indicate what sort of string is to be unpacked.
1865 See L<perlfunc/pack>.
1867 =item / must be followed by a*, A* or Z*
1869 (F) You had a pack template indicating a counted-length string,
1870 Currently the only things that can have their length counted are a*, A* or Z*.
1871 See L<perlfunc/pack>.
1873 =item / must follow a numeric type
1875 (F) You had an unpack template that contained a '#',
1876 but this did not follow some numeric unpack specification.
1877 See L<perlfunc/pack>.
1879 =item /%s/: Unrecognized escape \\%c passed through
1881 (W) You used a backslash-character combination which is not recognized
1882 by Perl. This combination appears in an interpolated variable or a
1883 C<'>-delimited regular expression. The character was understood literally.
1885 =item /%s/: Unrecognized escape \\%c in character class passed through
1887 (W) You used a backslash-character combination which is not recognized
1888 by Perl inside character classes. The character was understood literally.
1890 =item /%s/ should probably be written as "%s"
1892 (W) You have used a pattern where Perl expected to find a string,
1893 as in the first argument to C<join>. Perl will treat the true
1894 or false result of matching the pattern against $_ as the string,
1895 which is probably not what you had in mind.
1897 =item %s() called too early to check prototype
1899 (W) You've called a function that has a prototype before the parser saw a
1900 definition or declaration for it, and Perl could not check that the call
1901 conforms to the prototype. You need to either add an early prototype
1902 declaration for the subroutine in question, or move the subroutine
1903 definition ahead of the call to get proper prototype checking. Alternatively,
1904 if you are certain that you're calling the function correctly, you may put
1905 an ampersand before the name to avoid the warning. See L<perlsub>.
1907 =item %s argument is not a HASH or ARRAY element
1909 (F) The argument to exists() must be a hash or array element, such as:
1912 $ref->[12]->["susie"]
1914 =item %s argument is not a HASH or ARRAY element or slice
1916 (F) The argument to delete() must be either a hash or array element, such as:
1919 $ref->[12]->["susie"]
1921 or a hash or array slice, such as:
1923 @foo[$bar, $baz, $xyzzy]
1924 @{$ref->[12]}{"susie", "queue"}
1926 =item %s argument is not a subroutine name
1928 (F) The argument to exists() for C<exists &sub> must be a subroutine
1929 name, and not a subroutine call. C<exists &sub()> will generate this error.
1931 =item %s package attribute may clash with future reserved word: %s
1933 (W) A lowercase attribute name was used that had a package-specific handler.
1934 That name might have a meaning to Perl itself some day, even though it
1935 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1938 =item (in cleanup) %s
1940 (W) This prefix usually indicates that a DESTROY() method raised
1941 the indicated exception. Since destructors are usually called by
1942 the system at arbitrary points during execution, and often a vast
1943 number of times, the warning is issued only once for any number
1944 of failures that would otherwise result in the same message being
1947 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1948 could also result in this warning. See L<perlcall/G_KEEPERR>.
1950 =item <> should be quotes
1952 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1955 =item Attempt to join self
1957 (F) You tried to join a thread from within itself, which is an
1958 impossible task. You may be joining the wrong thread, or you may
1959 need to move the join() to some other thread.
1961 =item Bad evalled substitution pattern
1963 (F) You've used the /e switch to evaluate the replacement for a
1964 substitution, but perl found a syntax error in the code to evaluate,
1965 most likely an unexpected right brace '}'.
1967 =item Bad realloc() ignored
1969 (S) An internal routine called realloc() on something that had never been
1970 malloc()ed in the first place. Mandatory, but can be disabled by
1971 setting environment variable C<PERL_BADFREE> to 1.
1973 =item Bareword found in conditional
1975 (W) The compiler found a bareword where it expected a conditional,
1976 which often indicates that an || or && was parsed as part of the
1977 last argument of the previous construct, for example:
1981 It may also indicate a misspelled constant that has been interpreted
1984 use constant TYPO => 1;
1985 if (TYOP) { print "foo" }
1987 The C<strict> pragma is useful in avoiding such errors.
1989 =item Binary number > 0b11111111111111111111111111111111 non-portable
1991 (W) The binary number you specified is larger than 2**32-1
1992 (4294967295) and therefore non-portable between systems. See
1993 L<perlport> for more on portability concerns.
1995 =item Bit vector size > 32 non-portable
1997 (W) Using bit vector sizes larger than 32 is non-portable.
1999 =item Buffer overflow in prime_env_iter: %s
2001 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2002 %ENV, it encountered a logical name or symbol definition which was too long,
2003 so it was truncated to the string shown.
2005 =item Can't check filesystem of script "%s"
2007 (P) For some reason you can't check the filesystem of the script for nosuid.
2009 =item Can't declare class for non-scalar %s in "%s"
2011 (S) Currently, only scalar variables can declared with a specific class
2012 qualifier in a "my" or "our" declaration. The semantics may be extended
2013 for other types of variables in future.
2015 =item Can't declare %s in "%s"
2017 (F) Only scalar, array, and hash variables may be declared as "my" or
2018 "our" variables. They must have ordinary identifiers as names.
2020 =item Can't ignore signal CHLD, forcing to default
2022 (W) Perl has detected that it is being run with the SIGCHLD signal
2023 (sometimes known as SIGCLD) disabled. Since disabling this signal
2024 will interfere with proper determination of exit status of child
2025 processes, Perl has reset the signal to its default value.
2026 This situation typically indicates that the parent program under
2027 which Perl may be running (e.g. cron) is being very careless.
2029 =item Can't modify non-lvalue subroutine call
2031 (F) Subroutines meant to be used in lvalue context should be declared as
2032 such, see L<perlsub/"Lvalue subroutines">.
2034 =item Can't read CRTL environ
2036 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2037 from the CRTL's internal environment array and discovered the array was
2038 missing. You need to figure out where your CRTL misplaced its environ
2039 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2041 =item Can't remove %s: %s, skipping file
2043 (S) You requested an inplace edit without creating a backup file. Perl
2044 was unable to remove the original file to replace it with the modified
2045 file. The file was left unmodified.
2047 =item Can't return %s from lvalue subroutine
2049 (F) Perl detected an attempt to return illegal lvalues (such
2050 as temporary or readonly values) from a subroutine used as an lvalue.
2051 This is not allowed.
2053 =item Can't weaken a nonreference
2055 (F) You attempted to weaken something that was not a reference. Only
2056 references can be weakened.
2058 =item Character class [:%s:] unknown
2060 (F) The class in the character class [: :] syntax is unknown.
2063 =item Character class syntax [%s] belongs inside character classes
2065 (W) The character class constructs [: :], [= =], and [. .] go
2066 I<inside> character classes, the [] are part of the construct,
2067 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2068 are not currently implemented; they are simply placeholders for
2071 =item Constant is not %s reference
2073 (F) A constant value (perhaps declared using the C<use constant> pragma)
2074 is being dereferenced, but it amounts to the wrong type of reference. The
2075 message indicates the type of reference that was expected. This usually
2076 indicates a syntax error in dereferencing the constant value.
2077 See L<perlsub/"Constant Functions"> and L<constant>.
2079 =item constant(%s): %%^H is not localized
2081 (F) When setting compile-time-lexicalized hash %^H one should set the
2082 corresponding bit of $^H as well.
2084 =item constant(%s): %s
2086 (F) Compile-time-substitutions (such as overloaded constants and
2087 character names) were not correctly set up.
2089 =item defined(@array) is deprecated
2091 (D) defined() is not usually useful on arrays because it checks for an
2092 undefined I<scalar> value. If you want to see if the array is empty,
2093 just use C<if (@array) { # not empty }> for example.
2095 =item defined(%hash) is deprecated
2097 (D) defined() is not usually useful on hashes because it checks for an
2098 undefined I<scalar> value. If you want to see if the hash is empty,
2099 just use C<if (%hash) { # not empty }> for example.
2101 =item Did not produce a valid header
2105 =item Did you mean "local" instead of "our"?
2107 (W) Remember that "our" does not localize the declared global variable.
2108 You have declared it again in the same lexical scope, which seems superfluous.
2110 =item Document contains no data
2114 =item entering effective %s failed
2116 (F) While under the C<use filetest> pragma, switching the real and
2117 effective uids or gids failed.
2119 =item false [] range "%s" in regexp
2121 (W) A character class range must start and end at a literal character, not
2122 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2123 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2126 =item Filehandle %s opened only for output
2128 (W) You tried to read from a filehandle opened only for writing. If you
2129 intended it to be a read/write filehandle, you needed to open it with
2130 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2131 you intended only to read from the file, use "E<lt>". See
2134 =item flock() on closed filehandle %s
2136 (W) The filehandle you're attempting to flock() got itself closed some
2137 time before now. Check your logic flow. flock() operates on filehandles.
2138 Are you attempting to call flock() on a dirhandle by the same name?
2140 =item Global symbol "%s" requires explicit package name
2142 (F) You've said "use strict vars", which indicates that all variables
2143 must either be lexically scoped (using "my"), declared beforehand using
2144 "our", or explicitly qualified to say which package the global variable
2147 =item Hexadecimal number > 0xffffffff non-portable
2149 (W) The hexadecimal number you specified is larger than 2**32-1
2150 (4294967295) and therefore non-portable between systems. See
2151 L<perlport> for more on portability concerns.
2153 =item Ill-formed CRTL environ value "%s"
2155 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2156 environ array, and encountered an element without the C<=> delimiter
2157 used to spearate keys from values. The element is ignored.
2159 =item Ill-formed message in prime_env_iter: |%s|
2161 (W) A warning peculiar to VMS. Perl tried to read a logical name
2162 or CLI symbol definition when preparing to iterate over %ENV, and
2163 didn't see the expected delimiter between key and value, so the
2166 =item Illegal binary digit %s
2168 (F) You used a digit other than 0 or 1 in a binary number.
2170 =item Illegal binary digit %s ignored
2172 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2173 Interpretation of the binary number stopped before the offending digit.
2175 =item Illegal number of bits in vec
2177 (F) The number of bits in vec() (the third argument) must be a power of
2178 two from 1 to 32 (or 64, if your platform supports that).
2180 =item Integer overflow in %s number
2182 (W) The hexadecimal, octal or binary number you have specified either
2183 as a literal or as an argument to hex() or oct() is too big for your
2184 architecture, and has been converted to a floating point number. On a
2185 32-bit architecture the largest hexadecimal, octal or binary number
2186 representable without overflow is 0xFFFFFFFF, 037777777777, or
2187 0b11111111111111111111111111111111 respectively. Note that Perl
2188 transparently promotes all numbers to a floating point representation
2189 internally--subject to loss of precision errors in subsequent
2192 =item Invalid %s attribute: %s
2194 The indicated attribute for a subroutine or variable was not recognized
2195 by Perl or by a user-supplied handler. See L<attributes>.
2197 =item Invalid %s attributes: %s
2199 The indicated attributes for a subroutine or variable were not recognized
2200 by Perl or by a user-supplied handler. See L<attributes>.
2202 =item invalid [] range "%s" in regexp
2204 The offending range is now explicitly displayed.
2206 =item Invalid separator character %s in attribute list
2208 (F) Something other than a colon or whitespace was seen between the
2209 elements of an attribute list. If the previous attribute
2210 had a parenthesised parameter list, perhaps that list was terminated
2211 too soon. See L<attributes>.
2213 =item Invalid separator character %s in subroutine attribute list
2215 (F) Something other than a colon or whitespace was seen between the
2216 elements of a subroutine attribute list. If the previous attribute
2217 had a parenthesised parameter list, perhaps that list was terminated
2220 =item leaving effective %s failed
2222 (F) While under the C<use filetest> pragma, switching the real and
2223 effective uids or gids failed.
2225 =item Lvalue subs returning %s not implemented yet
2227 (F) Due to limitations in the current implementation, array and hash
2228 values cannot be returned in subroutines used in lvalue context.
2229 See L<perlsub/"Lvalue subroutines">.
2231 =item Method %s not permitted
2235 =item Missing %sbrace%s on \N{}
2237 (F) Wrong syntax of character name literal C<\N{charname}> within
2238 double-quotish context.
2240 =item Missing command in piped open
2242 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2243 construction, but the command was missing or blank.
2245 =item Missing name in "my sub"
2247 (F) The reserved syntax for lexically scoped subroutines requires that they
2248 have a name with which they can be found.
2250 =item No %s specified for -%c
2252 (F) The indicated command line switch needs a mandatory argument, but
2253 you haven't specified one.
2255 =item No package name allowed for variable %s in "our"
2257 (F) Fully qualified variable names are not allowed in "our" declarations,
2258 because that doesn't make much sense under existing semantics. Such
2259 syntax is reserved for future extensions.
2261 =item No space allowed after -%c
2263 (F) The argument to the indicated command line switch must follow immediately
2264 after the switch, without intervening spaces.
2266 =item no UTC offset information; assuming local time is UTC
2268 (S) A warning peculiar to VMS. Perl was unable to find the local
2269 timezone offset, so it's assuming that local system time is equivalent
2270 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2271 to translate to the number of seconds which need to be added to UTC to
2274 =item Octal number > 037777777777 non-portable
2276 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2277 and therefore non-portable between systems. See L<perlport> for more
2278 on portability concerns.
2280 See also L<perlport> for writing portable code.
2282 =item panic: del_backref
2284 (P) Failed an internal consistency check while trying to reset a weak
2287 =item panic: kid popen errno read
2289 (F) forked child returned an incomprehensible message about its errno.
2291 =item panic: magic_killbackrefs
2293 (P) Failed an internal consistency check while trying to reset all weak
2294 references to an object.
2296 =item Parentheses missing around "%s" list
2298 (W) You said something like
2304 my ($foo, $bar) = @_;
2306 Remember that "my", "our", and "local" bind tighter than comma.
2308 =item Possible Y2K bug: %s
2310 (W) You are concatenating the number 19 with another number, which
2311 could be a potential Year 2000 problem.
2313 =item Premature end of script headers
2317 =item Repeat count in pack overflows
2319 (F) You can't specify a repeat count so large that it overflows
2320 your signed integers. See L<perlfunc/pack>.
2322 =item Repeat count in unpack overflows
2324 (F) You can't specify a repeat count so large that it overflows
2325 your signed integers. See L<perlfunc/unpack>.
2327 =item realloc() of freed memory ignored
2329 (S) An internal routine called realloc() on something that had already
2332 =item Reference is already weak
2334 (W) You have attempted to weaken a reference that is already weak.
2335 Doing so has no effect.
2337 =item setpgrp can't take arguments
2339 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2340 unlike POSIX setpgid(), which takes a process ID and process group ID.
2342 =item Strange *+?{} on zero-length expression
2344 (W) You applied a regular expression quantifier in a place where it
2345 makes no sense, such as on a zero-width assertion.
2346 Try putting the quantifier inside the assertion instead. For example,
2347 the way to match "abc" provided that it is followed by three
2348 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2350 =item switching effective %s is not implemented
2352 (F) While under the C<use filetest> pragma, we cannot switch the
2353 real and effective uids or gids.
2355 =item This Perl can't reset CRTL environ elements (%s)
2357 =item This Perl can't set CRTL environ elements (%s=%s)
2359 (W) Warnings peculiar to VMS. You tried to change or delete an element
2360 of the CRTL's internal environ array, but your copy of Perl wasn't
2361 built with a CRTL that contained the setenv() function. You'll need to
2362 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2363 L<perlvms>) so that the environ array isn't the target of the change to
2364 %ENV which produced the warning.
2366 =item Unknown open() mode '%s'
2368 (F) The second argument of 3-argument open() is not among the list
2369 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2370 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2372 =item Unknown process %x sent message to prime_env_iter: %s
2374 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2375 iterating over it, and someone else stuck a message in the stream of
2376 data Perl expected. Someone's very confused, or perhaps trying to
2377 subvert Perl's population of %ENV for nefarious purposes.
2379 =item Unrecognized escape \\%c passed through
2381 (W) You used a backslash-character combination which is not recognized
2382 by Perl. The character was understood literally.
2384 =item Unterminated attribute parameter in attribute list
2386 (F) The lexer saw an opening (left) parenthesis character while parsing an
2387 attribute list, but the matching closing (right) parenthesis
2388 character was not found. You may need to add (or remove) a backslash
2389 character to get your parentheses to balance. See L<attributes>.
2391 =item Unterminated attribute list
2393 (F) The lexer found something other than a simple identifier at the start
2394 of an attribute, and it wasn't a semicolon or the start of a
2395 block. Perhaps you terminated the parameter list of the previous attribute
2396 too soon. See L<attributes>.
2398 =item Unterminated attribute parameter in subroutine attribute list
2400 (F) The lexer saw an opening (left) parenthesis character while parsing a
2401 subroutine attribute list, but the matching closing (right) parenthesis
2402 character was not found. You may need to add (or remove) a backslash
2403 character to get your parentheses to balance.
2405 =item Unterminated subroutine attribute list
2407 (F) The lexer found something other than a simple identifier at the start
2408 of a subroutine attribute, and it wasn't a semicolon or the start of a
2409 block. Perhaps you terminated the parameter list of the previous attribute
2412 =item Value of CLI symbol "%s" too long
2414 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2415 element from a CLI symbol table, and found a resultant string longer
2416 than 1024 characters. The return value has been truncated to 1024
2419 =item Version number must be a constant number
2421 (P) The attempt to translate a C<use Module n.n LIST> statement into
2422 its equivalent C<BEGIN> block found an internal inconsistency with
2427 =head1 Obsolete Diagnostics
2431 =item Character class syntax [: :] is reserved for future extensions
2433 (W) Within regular expression character classes ([]) the syntax beginning
2434 with "[:" and ending with ":]" is reserved for future extensions.
2435 If you need to represent those character sequences inside a regular
2436 expression character class, just quote the square brackets with the
2437 backslash: "\[:" and ":\]".
2439 =item Ill-formed logical name |%s| in prime_env_iter
2441 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2442 to iterate over %ENV which violates the syntactic rules governing logical
2443 names. Because it cannot be translated normally, it is skipped, and will not
2444 appear in %ENV. This may be a benign occurrence, as some software packages
2445 might directly modify logical name tables and introduce nonstandard names,
2446 or it may indicate that a logical name table has been corrupted.
2448 =item Probable precedence problem on %s
2450 (W) The compiler found a bareword where it expected a conditional,
2451 which often indicates that an || or && was parsed as part of the
2452 last argument of the previous construct, for example:
2456 =item regexp too big
2458 (F) The current implementation of regular expressions uses shorts as
2459 address offsets within a string. Unfortunately this means that if
2460 the regular expression compiles to longer than 32767, it'll blow up.
2461 Usually when you want a regular expression this big, there is a better
2462 way to do it with multiple statements. See L<perlre>.
2464 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2466 (D) Perl versions before 5.004 misinterpreted any type marker followed
2467 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2468 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2470 However, the developers of Perl 5.004 could not fix this bug completely,
2471 because at least two widely-used modules depend on the old meaning of
2472 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2473 old (broken) way inside strings; but it generates this message as a
2474 warning. And in Perl 5.005, this special treatment will cease.
2480 If you find what you think is a bug, you might check the
2481 articles recently posted to the comp.lang.perl.misc newsgroup.
2482 There may also be information at http://www.perl.com/perl/, the Perl
2485 If you believe you have an unreported bug, please run the B<perlbug>
2486 program included with your release. Make sure to trim your bug down
2487 to a tiny but sufficient test case. Your bug report, along with the
2488 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2489 analysed by the Perl porting team.
2493 The F<Changes> file for exhaustive details on what changed.
2495 The F<INSTALL> file for how to build Perl.
2497 The F<README> file for general stuff.
2499 The F<Artistic> and F<Copying> files for copyright information.
2503 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2504 contributions from The Perl Porters.
2506 Send omissions or corrections to <F<perlbug@perl.com>>.