3 perldelta - what's new for perl v5.6 (as of v5.005_62)
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 enhanced old
19 warnings 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 STOP is a new keyword
29 In addition to C<BEGIN>, C<INIT> and C<END>, subroutines named
30 C<STOP> are now special. They are queued up for execution at the
31 end of compilation, and cannot be called directly.
33 =item Treatment of list slices of undef has changed
35 When taking a slice of a literal list (as opposed to a slice of
36 an array or hash), Perl used to return an empty list if the
37 result happened to be composed of all undef values.
39 The new behavior is to produce an empty list if (and only if)
40 the original list was empty. Consider the following example:
42 @a = (1,undef,undef,2)[2,1,2];
44 The old behavior would have resulted in @a having no elements.
45 The new behavior ensures it has three undefined elements.
47 Note in particular that the behavior of slices of the following
48 cases remains unchanged:
52 @a = (anything_returning_empty_list())[2,1,2];
58 =item Possibly changed pseudo-random number generator
60 In 5.005_0x and earlier, perl's rand() function used the C library
61 rand(3) function. As of 5.005_52, Configure tests for drand48(),
62 random(), and rand() (in that order) and picks the first one it finds.
63 Perl programs that depend on reproducing a specific set of pseudo-random
64 numbers will now likely produce different output. You can use
65 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
67 =item Hashing function for hash keys has changed
69 Perl hashes are not order preserving. The apparently random order
70 encountered when iterating on the contents of a hash is determined
71 by the hashing algorithm used. To improve the distribution of lower
72 bits in the hashed value, the algorithm has changed slightly as of
73 5.005_52. When iterating over hashes, this may yield a random order
74 that is B<different> from that of previous versions.
76 =item C<undef> fails on read only values
78 Using the C<undef> operator on a readonly value (such as $1) has
79 the same effect as assigning C<undef> to the readonly value--it
82 =item Close-on-exec bit may be set on pipe() handles
84 On systems that support a close-on-exec flag on filehandles, the
85 flag will be set for any handles created by pipe(), if that is
86 warranted by the value of $^F that may be in effect. Earlier
87 versions neglected to set the flag for handles created with
88 pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
90 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
92 Perl 5.004 deprecated the interpretation of C<$$1> and
93 similar within interpolated strings to mean C<$$ . "1">,
96 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
98 =item values(%h) and C<\(%h)> operate on aliases to values, not copies
100 each(), values() and hashes in a list context return the actual
101 values in the hash, instead of copies (as they used to in earlier
102 versions). Typical idioms for using these constructs copy the
103 returned values, but this can make a significant difference when
104 creating references to the returned values.
106 Keys in the hash are still returned as copies when iterating on
109 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
111 vec() generates a run-time error if the BITS argument is not
112 a valid power-of-two integer.
114 =item Text of some diagnostic output has changed
116 Most references to internal Perl operations in diagnostics
117 have been changed to be more descriptive. This may be an
118 issue for programs that may incorrectly rely on the exact
119 text of diagnostics for proper functioning.
121 =item C<%@> has been removed
123 The undocumented special variable C<%@> that used to accumulate
124 "background" errors (such as those that happen in DESTROY())
125 has been removed, because it could potentially result in memory
128 =item Parenthesized not() behaves like a list operator
130 The C<not> operator now falls under the "if it looks like a function,
131 it behaves like a function" rule.
133 As a result, the parenthesized form can be used with C<grep> and C<map>.
134 The following construct used to be a syntax error before, but it works
137 grep not($_), @things;
139 On the other hand, using C<not> with a literal list slice may not
140 work. The following previously allowed construct:
142 print not (1,2,3)[0];
144 needs to written with additional parentheses now:
146 print not((1,2,3)[0]);
148 The behavior remains unaffected when C<not> is not followed by parentheses.
152 =head2 C Source Incompatibilities
156 =item C<PERL_POLLUTE>
158 Release 5.005 grandfathered old global symbol names by providing preprocessor
159 macros for extension source compatibility. As of release 5.6, these
160 preprocessor definitions are not available by default. You need to explicitly
161 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
162 extensions still using the old symbols, this option can be
163 specified via MakeMaker:
165 perl Makefile.PL POLLUTE=1
167 =item C<PERL_IMPLICIT_CONTEXT>
169 This new build option provides a set of macros for all API functions
170 such that an implicit interpreter/thread context argument is passed to
171 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
172 amounts to a macro invocation that actually translates to something like
173 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
174 to not have any significant source compatibility issues, the difference
175 between a macro and a real function call will need to be considered.
177 This means that there B<is> a source compatibility issue as a result of
178 this if your extensions attempt to use pointers to any of the Perl API
181 Note that the above issue is not relevant to the default build of
182 Perl, whose interfaces continue to match those of prior versions
183 (but subject to the other options described here).
185 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
186 with one of -Dusethreads, -Dusemultiplicity, or both.
188 See L<perlguts/"The Perl API"> for detailed information on the
189 ramifications of building Perl using this option.
191 =item C<PERL_POLLUTE_MALLOC>
193 Enabling Perl's malloc in release 5.005 and earlier caused
194 the namespace of system versions of the malloc family of functions to
195 be usurped by the Perl versions, since by default they used the
198 Besides causing problems on platforms that do not allow these functions to
199 be cleanly replaced, this also meant that the system versions could not
200 be called in programs that used Perl's malloc. Previous versions of Perl
201 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
202 EMBEDMYMALLOC preprocessor definitions.
204 As of release 5.6, Perl's malloc family of functions have default names
205 distinct from the system versions. You need to explicitly compile perl with
206 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
207 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
210 Note that these functions do B<not> constitute Perl's memory allocation API.
211 See L<perlguts/"Memory Allocation"> for further information about that.
215 =head2 Compatible C Source API Changes
219 =item C<PATCHLEVEL> is now C<PERL_VERSION>
221 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
222 are now available by default from perl.h, and reflect the base revision,
223 patchlevel, and subversion respectively. C<PERL_REVISION> had no
224 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
225 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
227 The new names cause less pollution of the B<cpp> namespace and reflect what
228 the numbers have come to stand for in common practice. For compatibility,
229 the old names are still supported when F<patchlevel.h> is explicitly
230 included (as required before), so there is no source incompatibility
233 =item Support for C++ exceptions
235 change#3386, also needs perlguts documentation
236 [TODO - Chip Salzenberg <chip@perlsupport.com>]
240 =head2 Binary Incompatibilities
242 The default build of this release is binary compatible with the 5.005
243 release or its maintenance versions.
245 The usethreads or usemultiplicity builds are B<not> binary compatible
246 with the corresponding builds in 5.005.
248 =head1 Installation and Configuration Improvements
250 =head2 New Configure flags
252 The following new flags may be enabled on the Configure command line
253 by running Configure with C<-Dflag>.
261 =head2 -Dusethreads and -Duse64bits now more daring
263 The Configure options enabling the use of threads and the use of
264 64-bitness are now more daring in the sense that they no more have
265 an explicit list of operating systems of known threads/64-bit
266 capabilities. In other words: if your operating system has the
267 necessary APIs, you should be able just to go ahead and use them.
268 See also L<"64-bit support">.
272 Some platforms have "long doubles", floating point numbers of even
273 larger range than ordinary "doubles". To enable using long doubles for
274 Perl's scalars, use -Duselongdouble.
278 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
279 See also L<"64-bit support">.
281 =head2 -Duselargefiles
283 Some platforms support large files, files larger than two gigabytes.
284 See L<"Large file support"> for more information.
286 =head2 installusrbinperl
288 You can use "Configure -Uinstallusrbinperl" which causes installperl
289 to skip installing perl also as /usr/bin/perl. This is useful if you
290 prefer not to modify /usr/bin for some reason or another but harmful
291 because many scripts assume to find Perl in /usr/bin/perl.
295 You can use "Configure -Dusesocks" which causes Perl to probe
296 for the SOCKS (v5, not v4) proxy protocol library,
297 http://www.socks.nec.com/
301 You can "post-edit" the Configure variables using the Configure C<-A>
302 flag. The editing happens immediately after the platform specific
303 hints files have been processed but before the actual configuration
304 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
306 =head2 Enhanced Installation Directories
308 The installation structure has been enriched to improve the support for
309 maintaining multiple versions of perl, to provide locations for
310 vendor-supplied modules and scripts, and to ease maintenance of
311 locally-added modules and scripts. See the section on Installation
312 Directories in the INSTALL file for complete details. For most users
313 building and installing from source, the defaults should be fine.
317 =head2 Unicode and UTF-8 support
319 Perl can optionally use UTF-8 as its internal representation for character
320 strings. The C<utf8> pragma enables this support in the current lexical
321 scope. See L<utf8> for more information.
323 =head2 Lexically scoped warning categories
325 You can now control the granularity of warnings emitted by perl at a finer
326 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
329 =head2 Lvalue subroutines
331 WARNING: This is an experimental feature.
334 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
335 Tuomas Lukka <lukka@fas.harvard.edu>)]
337 =head2 "our" declarations
339 An "our" declaration introduces a value that can be best understood
340 as a lexically scoped symbolic alias to a global variable in the
341 current package. This is mostly useful as an alternative to the
342 C<vars> pragma, but also provides the opportunity to introduce
343 typing and other attributes for such variables. See L<perlfunc/our>.
345 =head2 Weak references
347 WARNING: This is an experimental feature.
349 change#3385, also need perlguts documentation
351 [TODO - Tuomas Lukka <lukka@fas.harvard.edu>]
353 =head2 File globbing implemented internally
355 WARNING: This is currently an experimental feature. Interfaces and
356 implementation are likely to change.
358 Perl now uses the File::Glob implementation of the glob() operator
359 automatically. This avoids using an external csh process and the
360 problems associated with it.
362 =head2 Binary numbers supported
364 Binary numbers are now supported as literals, in s?printf formats, and
368 printf "The answer is: %b\n", oct("0b101010");
370 =head2 Some arrows may be omitted in calls through references
372 Perl now allows the arrow to be omitted in many constructs
373 involving subroutine calls through references. For example,
374 C<$foo[10]->('foo')> may now be written C<$foo[10]('foo')>.
375 This is rather similar to how the arrow may be omitted from
376 C<$foo[10]->{'foo'}>. Note however, that the arrow is still
377 required for C<foo(10)->('bar')>.
379 =head2 syswrite() ease-of-use
381 The length argument of C<syswrite()> has become optional.
383 =head2 Filehandles can be autovivified
385 Similar to how constructs such as C<$x->[0]> autovivify a reference,
386 open() now autovivifies a filehandle if the first argument is an
387 uninitialized variable. This allows the constructs C<open(my $fh, ...)> and
388 C<open(local $fh,...)> to be used to create filehandles that will
389 conveniently be closed automatically when the scope ends, provided there
390 are no other references to them. This largely eliminates the need for
391 typeglobs when opening filehandles that must be passed around, as in the
396 or die "Can't open '@_': $!";
401 my $f = myopen("</etc/motd");
403 # $f implicitly closed here
406 [TODO - this idiom needs more pod penetration]
408 =head2 64-bit support
410 All platforms that have 64-bit integers either (a) natively as longs
411 or ints (b) via special compiler flags (c) using long long are able to
412 use "quads" (64-integers) as follows:
418 constants (decimal, hexadecimal, octal, binary) in the code
422 arguments to oct() and hex()
426 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
434 pack() and unpack() "q" and "Q" formats
438 in basic arithmetics: + - * / %
442 vec() (but see the below note about bit arithmetics)
446 Note that unless you have the case (a) you will have to configure
447 and compile Perl using the -Duse64bits Configure flag.
449 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
450 64-bit clean, they are explictly forced to be 32-bit. Bit arithmetics
451 for bit vectors (created by vec()) are not limited in their width.
453 Last but not least: note that due to Perl's habit of always using
454 floating point numbers the quads are still not true integers.
455 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
456 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
457 are silently promoted to floating point numbers, after which they will
458 start losing precision (their lower digits).
460 =head2 Large file support
462 If you have filesystems that support "large files" (files larger than
463 2 gigabytes), you may now also be able to create and access them from
464 Perl. You have to use Configure -Duselargefiles. Turning on the
465 large file support turns on also the 64-bit support, for obvious reasons.
467 Note that in addition to requiring a proper file system to do large
468 files you may also need to adjust your per-process (or your
469 per-system, or per-process-group, or per-user-group) maximum filesize
470 limits before running Perl scripts that try to handle large files,
471 especially if you intend to write such files.
473 Finally, in addition to your process/process group maximum filesize
474 limits, you may have quota limits on your filesystems that stop you
475 (your user id or your user group id) from using large files.
477 Adjusting your process/user/group/file system/operating system limits
478 is outside the scope of Perl core language. For process limits, you
479 may try increasing the limits using your shell's limits/limit/ulimit
480 command before running Perl. The BSD::Resource extension (not
481 included with the standard Perl distribution) may also be of use, it
482 offers the getrlimit/setrlimit interface that can be used to adjust
483 process resource usage limits, including the maximum filesize limit.
487 In some systems you may be able to use long doubles to enhance the
488 range of precision of your double precision floating point numbers
489 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
490 this support (if it is available).
494 You can Configure -Dusemorebits to turn on both the 64-bit support
495 and the long double support.
497 =head2 Enhanced support for sort() subroutines
499 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
500 now be used as sort subroutines. In either case, the two elements to
501 be compared as passed as normal parameters in @_. See L<perlfunc/sort>.
503 For unprototyped sort subroutines, the historical behavior of passing
504 the elements to be compared as the global variables $a and $b remains
507 =head2 Better syntax checks on parenthesized unary operators
511 print defined(&foo,&bar,&baz);
512 print uc("foo","bar","baz");
515 used to be accidentally allowed in earlier versions, and produced
516 unpredictable behaviour. Some produced ancillary warnings
517 when used in this way; others silently did the wrong thing.
519 The parenthesized forms of most unary operators that expect a single
520 argument now ensure that they are not called with more than one
521 argument, making the cases shown above syntax errors. The usual
524 print defined &foo, &bar, &baz;
525 print uc "foo", "bar", "baz";
528 remains unchanged. See L<perlop>.
530 =head2 POSIX character class syntax [: :] supported
532 For example to match alphabetic characters use /[[:alpha:]]/.
533 See L<perlre> for details.
535 =head2 Improved C<qw//> operator
537 The C<qw//> operator is now evaluated at compile time into a true list
538 instead of being replaced with a run time call to C<split()>. This
539 removes the confusing misbehaviour of C<qw//> in scalar context, which
540 had inherited that behaviour from split().
544 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
546 now correctly prints "3|a", instead of "2|a".
548 =head2 pack() format 'Z' supported
550 The new format type 'Z' is useful for packing and unpacking null-terminated
551 strings. See L<perlfunc/"pack">.
553 =head2 pack() format modifier '!' supported
555 The new format type modifier '!' is useful for packing and unpacking
556 native shorts, ints, and longs. See L<perlfunc/"pack">.
558 =head2 pack() and unpack() support counted strings
560 The template character '/' can be used to specify a counted string
561 type to be packed or unpacked. See L<perlfunc/"pack">.
563 =head2 Comments in pack() templates
565 The '#' character in a template introduces a comment up to
566 end of the line. This facilitates documentation of pack()
569 =head2 $^X variables may now have names longer than one character
571 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
572 error. Now variable names that begin with a control character may be
573 arbitrarily long. However, for compatibility reasons, these variables
574 I<must> be written with explicit braces, as C<${^XY}> for example.
575 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
576 than one control character, such as C<${^XY^Z}>, are illegal.
578 The old syntax has not changed. As before, `^X' may be either a
579 literal control-X character or the two-character sequence `caret' plus
580 `X'. When braces are omitted, the variable name stops after the
581 control character. Thus C<"$^XYZ"> continues to be synonymous with
582 C<$^X . "YZ"> as before.
584 As before, lexical variables may not have names beginning with control
585 characters. As before, variables whose names begin with a control
586 character are always forced to be in package `main'. All such variables
587 are reserved for future extensions, except those that begin with
588 C<^_>, which may be used by user programs and are guaranteed not to
589 acquire special meaning in any future version of Perl.
591 =head2 C<use attrs> implicit in subroutine attributes
593 Formerly, if you wanted to mark a subroutine as being a method call or
594 as requiring an automatic lock() when it is entered, you had to declare
595 that with a C<use attrs> pragma in the body of the subroutine.
596 That can now be accomplished with a declaration syntax, like this:
598 sub mymethod : locked, method ;
600 sub mymethod : locked, method {
604 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
605 with the stubs they provide. See L<attributes>.
607 =head2 Regular expression improvements
609 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
610 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
612 =head2 Overloading improvements
615 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
617 =head2 open() with more than two arguments
619 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
621 =head2 Support for interpolating named characters
624 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
626 =head2 Experimental support for user-hooks in @INC
628 [TODO - Ken Fox <kfox@ford.com>]
630 =head2 C<require> and C<do> may be overridden
632 C<require> and C<do 'file'> operations may be overridden locally
633 by importing subroutines of the same name into the current package
634 (or globally by importing them into the CORE::GLOBAL:: namespace).
635 Overriding C<require> will also affect C<use>, provided the override
636 is visible at compile-time.
637 See L<perlsub/"Overriding Built-in Functions">.
639 =head2 New variable $^C reflects C<-c> switch
641 C<$^C> has a boolean value that reflects whether perl is being run
642 in compile-only mode (i.e. via the C<-c> switch). Since
643 BEGIN blocks are executed under such conditions, this variable
644 enables perl code to determine whether actions that make sense
645 only during normal running are warranted. See L<perlvar>.
649 Arbitrary code can be queued for execution when Perl has finished
650 parsing the program (i.e. when the compile phase ends) using STOP
651 blocks. These behave similar to END blocks, except for being
652 called at the end of compilation rather than at the end of execution.
654 =head2 Optional Y2K warnings
656 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
657 it emits optional warnings when concatenating the number 19
660 This behavior must be specifically enabled when running Configure.
661 See L<INSTALL> and L<README.Y2K>.
663 =head1 Significant bug fixes
665 =head2 E<lt>HANDLEE<gt> on empty files
667 With C<$/> set to C<undef>, slurping an empty file returns a string of
668 zero length (instead of C<undef>, as it used to) the first time the
669 HANDLE is read. Further reads yield C<undef>.
671 This means that the following will append "foo" to an empty file (it used
674 perl -0777 -pi -e 's/^/foo/' empty_file
678 perl -pi -e 's/^/foo/' empty_file
680 is unchanged (it continues to leave the file empty).
682 =head2 C<eval '...'> improvements
684 Line numbers (as reflected by caller() and most diagnostics) within
685 C<eval '...'> were often incorrect when here documents were involved.
686 This has been corrected.
688 Lexical lookups for variables appearing in C<eval '...'> within
689 functions that were themselves called within an C<eval '...'> were
690 searching the wrong place for lexicals. The lexical search now
691 correctly ends at the subroutine's block boundary.
693 Parsing of here documents used to be flawed when they appeared as
694 the replacement expression in C<eval 's/.../.../e'>. This has
697 =head2 All compilation errors are true errors
699 Some "errors" encountered at compile time were by neccessity
700 generated as warnings followed by eventual termination of the
701 program. This enabled more such errors to be reported in a
702 single run, rather than causing a hard stop at the first error
703 that was encountered.
705 The mechanism for reporting such errors has been reimplemented
706 to queue compile-time errors and report them at the end of the
707 compilation as true errors rather than as warnings. This fixes
708 cases where error messages leaked through in the form of warnings
709 when code was compiled at run time using C<eval STRING>, and
710 also allows such errors to be reliably trapped using __DIE__ hooks.
712 =head2 Automatic flushing of output buffers
714 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
715 of all files opened for output when the operation
716 was attempted. This mostly eliminates confusing
717 buffering mishaps suffered by users unaware of how Perl internally
720 =head2 Better diagnostics on meaningless filehandle operations
722 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
723 are compile time errors. Attempting to read from filehandles that
724 were opened only for writing will now produce warnings (just as
725 writing to read-only filehandles does).
727 =head2 Where possible, buffered data discarded from duped input filehandle
729 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
730 was previously read and buffered in C<OLD> before duping the handle.
731 On platforms where doing this is allowed, the next read operation
732 on C<NEW> will return the same data as the corresponding operation
733 on C<OLD>. Formerly, it would have returned the data from the start
734 of the following disk block instead.
736 =head2 system(), backticks and pipe open now reflect exec() failure
738 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
739 etc., are implemented via fork() and exec(). When the underlying
740 exec() fails, earlier versions did not report the error properly,
741 since the exec() happened to be in a different process.
743 The child process now communicates with the parent about the
744 error in launching the external command, which allows these
745 constructs to return with their usual error value and set $!.
747 =head2 Implicitly closed filehandles are safer
749 Sometimes implicitly closed filehandles (as when they are localized,
750 and Perl automatically closes them on exiting the scope) could
751 inadvertently set $? or $!. This has been corrected.
753 =head2 C<(\$)> prototype and C<$foo{a}>
755 An scalar reference prototype now correctly allows a hash or
756 array element in that slot.
758 =head2 Pseudo-hashes work better
760 Dereferencing some types of reference values in a pseudo-hash,
761 such as C<$ph->{foo}[1]>, was accidentally disallowed. This has
764 When applied to a pseudo-hash element, exists() now reports whether
765 the specified value exists, not merely if the key is valid.
767 =head2 C<goto &sub> and AUTOLOAD
769 The C<goto &sub> construct works correctly when C<&sub> happens
772 =head2 C<-bareword> allowed under C<use integer>
774 The autoquoting of barewords preceded by C<-> did not work
775 in prior versions when the C<integer> pragma was enabled.
778 =head2 Boolean assignment operators are legal lvalues
780 Constructs such as C<($a ||= 2) += 1> are now allowed.
782 =head2 C<sort $coderef @foo> allowed
784 sort() did not accept a subroutine reference as the comparison
785 function in earlier versions. This is now permitted.
787 =head2 Failures in DESTROY()
789 When code in a destructor threw an exception, it went unnoticed
790 in earlier versions of Perl, unless someone happened to be
791 looking in $@ just after the point the destructor happened to
792 run. Such failures are now visible as warnings when warnings are
795 =head2 Locale bugs fixed
797 printf() and sprintf() previously reset the numeric locale
798 back to the default "C" locale. This has been fixed.
800 Numbers formatted according to the local numeric locale
801 (such as using a decimal comma instead of a decimal dot) caused
802 "isn't numeric" warnings, even while the operations accessing
803 those numbers produced correct results. The warnings are gone.
807 The C<eval 'return sub {...}'> construct could sometimes leak
808 memory. This has been fixed.
810 Operations that aren't filehandle constructors used to leak memory
811 when used on invalid filehandles. This has been fixed.
813 Constructs that modified C<@_> could fail to deallocate values
814 in C<@_> and thus leak memory. This has been corrected.
816 =head2 Spurious subroutine stubs after failed subroutine calls
818 Perl could sometimes create empty subroutine stubs when a
819 subroutine was not found in the package. Such cases stopped
820 later method lookups from progressing into base packages.
821 This has been corrected.
823 =head2 Consistent numeric conversions
826 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
828 =head2 Taint failures under C<-U>
830 When running in unsafe mode, taint violations could sometimes
831 cause silent failures. This has been fixed.
833 =head2 END blocks and the C<-c> switch
835 Prior versions used to run BEGIN B<and> END blocks when Perl was
836 run in compile-only mode. Since this is typically not the expected
837 behavior, END blocks are not executed anymore when the C<-c> switch
840 See L<STOP blocks> for how to run things when the compile phase ends.
842 =head2 Potential to leak DATA filehandles
844 Using the C<__DATA__> token creates an implicit filehandle to
845 the file that contains the token. It is the program's
846 responsibility to close it when it is done reading from it.
848 This caveat is now better explained in the documentation.
851 =head2 Diagnostics follow STDERR
853 Diagnostic output now goes to whichever file the C<STDERR> handle
854 is pointing at, instead of always going to the underlying C runtime
857 =head2 Other fixes for better diagnostics
859 Line numbers are no longer suppressed (under most likely circumstances)
860 during the global destruction phase.
862 Diagnostics emitted from code running in threads other than the main
863 thread are now accompanied by the thread ID.
865 Embedded null characters in diagnostics now actually show up. They
866 used to truncate the message in prior versions.
868 $foo::a and $foo::b are now exempt from "possible typo" warnings only
869 if sort() is encountered in package foo.
871 Unrecognized alphabetic escapes encountered when parsing quote
872 constructs now generate a warning, since they may take on new
873 semantics in later versions of Perl.
875 =head1 Performance enhancements
877 =head2 Simple sort() using { $a <=> $b } and the like are optimized
879 Many common sort() operations using a simple inlined block are now
880 optimized for faster performance.
882 =head2 Optimized assignments to lexical variables
884 Certain operations in the RHS of assignment statements have been
885 optimized to directly set the lexical variable on the LHS,
886 eliminating redundant copying overheads.
888 =head2 Method lookups optimized
890 [TODO - Chip Salzenberg <chip@perlsupport.com>]
892 =head2 Faster mechanism to invoke XSUBs
895 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
897 =head2 Perl_malloc() improvements
900 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
902 =head2 Faster subroutine calls
904 Minor changes in how subroutine calls are handled internally
905 provide marginal improvements in performance.
907 =head1 Platform specific changes
909 =head2 Additional supported platforms
915 VM/ESA is now supported.
919 Siemens BS2000 is now supported under the POSIX Shell.
923 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
928 GNU/Hurd is now supported.
932 Rhapsody is now supported.
936 EPOC is is now supported (on Psion 5).
946 Perl now works with djgpp 2.02 (and 2.03 alpha).
950 Environment variable names are not converted to uppercase any more.
954 Wrong exit code from backticks now fixed.
958 This port is still using its own builtin globbing.
964 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
968 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
972 Site library searches failed to look for ".../site/5.XXX/lib"
973 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
975 When given a pathname that consists only of a drivename, such
976 as C<A:>, opendir() and stat() now use the current working
977 directory for the drive rather than the drive root.
979 The builtin XSUB functions in the Win32:: namespace are
980 documented. See L<Win32>.
982 $^X now contains the full path name of the running executable.
984 A Win32::GetLongPathName() function is provided to complement
985 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
987 POSIX::uname() is supported.
989 system(1,...) now returns true process IDs rather than process
990 handles. kill() accepts any real process id, rather than strictly
991 return values from system(1,...).
993 The C<Shell> module is supported.
995 Rudimentary support for building under command.com in Windows 95
1006 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1010 IO constants (SEEK_*, _IO*).
1014 Directory-related IO methods (new, read, close, rewind, tied delete).
1016 =item lib/io_multihomed
1018 INET sockets with multi-homed hosts.
1030 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1034 File test operators.
1038 Verify operations that access pad objects (lexicals and temporaries).
1042 =head1 Modules and Pragmata
1050 While used internally by Perl as a pragma, this module also
1051 provides a way to fetch subroutine and variable attributes.
1056 The Perl Compiler suite has been extensively reworked for this
1059 [TODO - Vishal Bhatia <vishal@gol.com>,
1060 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1064 The ByteLoader is a dedicated extension to generate and run
1065 Perl bytecode. See L<ByteLoader>.
1069 References can now be used. See L<constant>.
1074 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1078 A C<Maxdepth> setting can be specified to avoid venturing
1079 too deeply into deep data structures. See L<Data::Dumper>.
1081 Dumping C<qr//> objects works correctly.
1085 C<DB> is an experimental module that exposes a clean abstraction
1086 to Perl's debugging API.
1090 [TODO - Paul Marquess <paul.marquess@bt.com>]
1094 Devel::DProf, a Perl source code profiler has been added. See
1095 L<Devel::DProf> and L<dprofpp>.
1099 The Dumpvalue module provides screen dumps of Perl data.
1103 Overall, Benchmark results exhibit lower average error and better timing
1106 You can now run tests for I<n> seconds instead of guessing the right
1107 number of tests to run: e.g. timethese(-5, ...) will run each
1108 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1109 means "for at least 3 CPU seconds". The output format has also
1110 changed. For example:
1112 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1114 will now output something like this:
1116 Benchmark: running a, b, each for at least 5 CPU seconds...
1117 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1118 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1120 New features: "each for at least N CPU seconds...", "wallclock secs",
1121 and the "@ operations/CPU second (n=operations)".
1123 timethese() now returns a reference to a hash of Benchmark objects containing
1124 the test results, keyed on the names of the tests.
1126 timethis() now returns the iterations field in the Benchmark result object
1129 timethese(), timethis(), and the new cmpthese() (see below) can also take
1130 a format specifier of 'none' to suppress output.
1132 A new function countit() is just like timeit() except that it takes a
1133 TIME instead of a COUNT.
1135 A new function cmpthese() prints a chart comparing the results of each test
1136 returned from a timethese() call. For each possible pair of tests, the
1137 percentage speed difference (iters/sec or seconds/iter) is shown.
1139 For other details, see L<Benchmark>.
1143 The Devel::Peek module provides access to the internal representation
1144 of Perl variables and data. It is a data debugging tool for the XS programmer.
1146 =item ExtUtils::MakeMaker
1148 change#4135, also needs docs in module pod
1149 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1153 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1154 large (more than 4G) file access (64-bit support is not yet
1155 working, though, so no need to get overly excited), Free/Net/OpenBSD
1156 locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
1157 O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
1161 A compare_text() function has been added, which allows custom
1162 comparison functions. See L<File::Compare>.
1166 File::Find now works correctly when the wanted() function is either
1167 autoloaded or is a symbolic reference.
1169 A bug that caused File::Find to lose track of the working directory
1170 when pruning top-level directories has been fixed.
1172 File::Find now also supports several other options to control its
1173 behavior. It can follow symbolic links if the C<follow> option is
1174 specified. Enabling the C<no_chdir> option will make File::Find skip
1175 changing the current directory when walking directories. The C<untaint>
1176 flag can be useful when running with taint checks enabled.
1182 This extension implements BSD-style file globbing. By default,
1183 it will also be used for the internal implementation of the glob()
1184 operator. See L<File::Glob>.
1188 New methods have been added to the File::Spec module: devnull() returns
1189 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1190 the temp directory (normally /tmp on Unix). There are now also methods
1191 to convert between absolute and relative filenames: abs2rel() and
1192 rel2abs(). For compatibility with operating systems that specify volume
1193 names in file paths, the splitpath(), splitdir(), and catdir() methods
1196 =item File::Spec::Functions
1198 The new File::Spec::Functions modules provides a function interface
1199 to the File::Spec module. Allows shorthand
1201 $fullname = catfile($dir1, $dir2, $file);
1205 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1209 Getopt::Long licensing has changed to allow the Perl Artistic License
1210 as well as the GPL. It used to be GPL only, which got in the way of
1211 non-GPL applications that wanted to use Getopt::Long.
1213 Getopt::Long encourages the use of Pod::Usage to produce help
1214 messages. For example:
1220 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1221 pod2usage(1) if $help;
1222 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1228 sample - Using GetOpt::Long and Pod::Usage
1232 sample [options] [file ...]
1235 -help brief help message
1236 -man full documentation
1244 Print a brief help message and exits.
1248 Prints the manual page and exits.
1254 B<This program> will read the given input file(s) and do someting
1255 useful with the contents thereof.
1259 See L<Pod::Usage> for details.
1261 A bug that prevented the non-option call-back E<lt>E<gt> from being
1262 specified as the first argument has been fixed.
1264 To specify the characters E<lt> and E<gt> as option starters, use
1265 E<gt>E<lt>. Note, however, that changing option starters is strongly
1270 write() and syswrite() will now accept a single-argument
1271 form of the call, for consistency with Perl's syswrite().
1273 You can now create a TCP-based IO::Socket::INET without forcing
1274 a connect attempt. This allows you to configure its options
1275 (like making it non-blocking) and then call connect() manually.
1277 A bug that prevented the IO::Socket::protocol() accessor
1278 from ever returning the correct value has been corrected.
1282 Java Perl Lingo is now distributed with Perl. See jpl/README
1283 for more information.
1287 C<use lib> now weeds out any trailing duplicate entries.
1288 C<no lib> removes all named entries.
1292 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1293 and C<~> are now supported on bigints.
1297 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1298 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1302 A little bit of radial trigonometry (cylindrical and spherical),
1303 radial coordinate conversions, and the great circle distance were added.
1307 [TODO - Brad Appleton <bradapp@enteract.com>]
1309 =item Pod::Text and Pod::Man
1311 [TODO - Russ Allbery <rra@stanford.edu>]
1315 An EXISTS method has been added to this module (and sdbm_exists() has
1316 been added to the underlying sdbm library), so one can now call exists
1317 on an SDBM_File tied hash and get the correct result, rather than a
1320 A bug that may have caused data loss when more than one disk block
1321 happens to be read from the database in a single FETCH() has been
1326 The timelocal() and timegm() functions used to silently return bogus
1327 results when the date fell outside the machine's integer range. They
1328 now consistently croak() if the date falls in an unsupported range.
1332 The error return value in list context has been changed for all functions
1333 that return a list of values. Previously these functions returned a list
1334 with a single element C<undef> if an error occurred. Now these functions
1335 return the empty list in these situations. This applies to the following
1341 The remaining functions are unchanged and continue to return C<undef> on
1342 error even in list context.
1344 The Win32::SetLastError(ERROR) function has been added as a complement
1345 to the Win32::GetLastError() function.
1347 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1348 pathname for FILENAME in scalar context. In list context it returns
1349 a two-element list containing the fully qualified directory name and
1350 the filename. See L<Win32>.
1354 A new feature called "DBM Filters" has been added to all the
1355 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1356 DBM Filters add four new methods to each DBM module:
1363 These can be used to filter key-value pairs before the pairs are
1364 written to the database or just after they are read from the database.
1365 See L<perldbmfilter> for further information.
1371 C<use attrs> is now obsolete, and is only provided for
1372 backward-compatibility. It's been replaced by the C<sub : attributes>
1373 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1375 C<use utf8> to enable UTF-8 and Unicode support.
1377 C<use caller 'encoding'> allows modules to inherit pragmatic attributes
1378 from the caller's context. C<encoding> is currently the only supported
1381 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1384 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1385 ...). Currently only one subpragma implemented, "use filetest
1386 'access';", that uses access(2) or equivalent to check permissions
1387 instead of using stat(2) as usual. This matters in filesystems
1388 where there are ACLs (access control lists): the stat(2) might lie,
1389 but access(2) knows better.
1391 =head1 Utility Changes
1395 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1399 C<perlcc> now supports the C and Bytecode backends. By default,
1400 it generates output from the simple C backend rather than the
1401 optimized C backend.
1403 Support for non-Unix platforms has been improved.
1408 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1410 =head1 Documentation Changes
1414 =item perlcompile.pod
1416 An introduction to using the Perl Compiler suite.
1418 =item perlfilter.pod
1420 An introduction to writing Perl source filters.
1424 Some guidelines for hacking the Perl source code.
1426 =item perlopentut.pod
1428 A tutorial on using open() effectively.
1430 =item perlreftut.pod
1432 A tutorial that introduces the essentials of references.
1436 A tutorial on managing class data for object modules.
1440 =head1 New or Changed Diagnostics
1444 =item "my sub" not yet implemented
1446 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1449 =item '!' allowed only after types %s
1451 (F) The '!' is allowed in pack() and unpack() only after certain types.
1452 See L<perlfunc/pack>.
1454 =item / cannot take a count
1456 (F) You had an unpack template indicating a counted-length string,
1457 but you have also specified an explicit size for the string.
1458 See L<perlfunc/pack>.
1460 =item / must be followed by a, A or Z
1462 (F) You had an unpack template indicating a counted-length string,
1463 which must be followed by one of the letters a, A or Z
1464 to indicate what sort of string is to be unpacked.
1465 See L<perlfunc/pack>.
1467 =item / must be followed by a*, A* or Z*
1469 (F) You had a pack template indicating a counted-length string,
1470 Currently the only things that can have their length counted are a*, A* or Z*.
1471 See L<perlfunc/pack>.
1473 =item / must follow a numeric type
1475 (F) You had an unpack template that contained a '#',
1476 but this did not follow some numeric unpack specification.
1477 See L<perlfunc/pack>.
1479 =item /%s/: Unrecognized escape \\%c passed through
1481 (W) You used a backslash-character combination which is not recognized
1482 by Perl. This combination appears in an interpolated variable or a
1483 C<'>-delimited regular expression. The character was understood literally.
1485 =item /%s/: Unrecognized escape \\%c in character class passed through
1487 (W) You used a backslash-character combination which is not recognized
1488 by Perl inside character classes. The character was understood literally.
1490 =item /%s/ should probably be written as "%s"
1492 (W) You have used a pattern where Perl expected to find a string,
1493 as in the first argument to C<join>. Perl will treat the true
1494 or false result of matching the pattern against $_ as the string,
1495 which is probably not what you had in mind.
1497 =item %s() called too early to check prototype
1499 (W) You've called a function that has a prototype before the parser saw a
1500 definition or declaration for it, and Perl could not check that the call
1501 conforms to the prototype. You need to either add an early prototype
1502 declaration for the subroutine in question, or move the subroutine
1503 definition ahead of the call to get proper prototype checking. Alternatively,
1504 if you are certain that you're calling the function correctly, you may put
1505 an ampersand before the name to avoid the warning. See L<perlsub>.
1507 =item %s package attribute may clash with future reserved word: %s
1509 (W) A lowercase attribute name was used that had a package-specific handler.
1510 That name might have a meaning to Perl itself some day, even though it
1511 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1514 =item (in cleanup) %s
1516 (W) This prefix usually indicates that a DESTROY() method raised
1517 the indicated exception. Since destructors are usually called by
1518 the system at arbitrary points during execution, and often a vast
1519 number of times, the warning is issued only once for any number
1520 of failures that would otherwise result in the same message being
1523 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1524 could also result in this warning. See L<perlcall/G_KEEPERR>.
1526 =item <> should be quotes
1528 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1531 =item Attempt to join self
1533 (F) You tried to join a thread from within itself, which is an
1534 impossible task. You may be joining the wrong thread, or you may
1535 need to move the join() to some other thread.
1537 =item Bad evalled substitution pattern
1539 (F) You've used the /e switch to evaluate the replacement for a
1540 substitution, but perl found a syntax error in the code to evaluate,
1541 most likely an unexpected right brace '}'.
1543 =item Bad realloc() ignored
1545 (S) An internal routine called realloc() on something that had never been
1546 malloc()ed in the first place. Mandatory, but can be disabled by
1547 setting environment variable C<PERL_BADFREE> to 1.
1549 =item Binary number > 0b11111111111111111111111111111111 non-portable
1551 (W) The binary number you specified is larger than 2**32-1
1552 (4294967295) and therefore non-portable between systems. See
1553 L<perlport> for more on portability concerns.
1555 =item Bit vector size > 32 non-portable
1557 (W) Using bit vector sizes larger than 32 is non-portable.
1559 =item Buffer overflow in prime_env_iter: %s
1561 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
1562 %ENV, it encountered a logical name or symbol definition which was too long,
1563 so it was truncated to the string shown.
1565 =item Can't check filesystem of script "%s"
1567 (P) For some reason you can't check the filesystem of the script for nosuid.
1569 =item Can't ignore signal CHLD, forcing to default
1571 (W) Perl has detected that it is being run with the SIGCHLD signal
1572 (sometimes known as SIGCLD) disabled. Since disabling this signal
1573 will interfere with proper determination of exit status of child
1574 processes, Perl has reset the signal to its default value.
1575 This situation typically indicates that the parent program under
1576 which Perl may be running (e.g. cron) is being very careless.
1578 =item Can't modify non-lvalue subroutine call
1580 (F) Subroutines meant to be used in lvalue context should be declared as
1581 such, see L<perlsub/"Lvalue subroutines">.
1583 =item Can't read CRTL environ
1585 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1586 from the CRTL's internal environment array and discovered the array was
1587 missing. You need to figure out where your CRTL misplaced its environ
1588 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1590 =item Can't remove %s: %s, skipping file
1592 (S) You requested an inplace edit without creating a backup file. Perl
1593 was unable to remove the original file to replace it with the modified
1594 file. The file was left unmodified.
1596 =item Can't return %s from lvalue subroutine
1598 (F) Perl detected an attempt to return illegal lvalues (such
1599 as temporary or readonly values) from a subroutine used as an lvalue.
1600 This is not allowed.
1602 =item Can't weaken a nonreference
1604 (F) You attempted to weaken something that was not a reference. Only
1605 references can be weakened.
1607 =item Character class [:%s:] unknown
1609 (F) The class in the character class [: :] syntax is unknown.
1612 =item Character class syntax [%s] belongs inside character classes
1614 (W) The character class constructs [: :], [= =], and [. .] go
1615 I<inside> character classes, the [] are part of the construct,
1616 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1617 are not currently implemented; they are simply placeholders for
1620 =item Constant is not %s reference
1622 (F) A constant value (perhaps declared using the C<use constant> pragma)
1623 is being dereferenced, but it amounts to the wrong type of reference. The
1624 message indicates the type of reference that was expected. This usually
1625 indicates a syntax error in dereferencing the constant value.
1626 See L<perlsub/"Constant Functions"> and L<constant>.
1628 =item constant(%s): %%^H is not localized
1630 (F) When setting compile-time-lexicalized hash %^H one should set the
1631 corresponding bit of $^H as well.
1633 =item constant(%s): %s
1635 (F) Compile-time-substitutions (such as overloaded constants and
1636 character names) were not correctly set up.
1638 =item defined(@array) is deprecated
1640 (D) defined() is not usually useful on arrays because it checks for an
1641 undefined I<scalar> value. If you want to see if the array is empty,
1642 just use C<if (@array) { # not empty }> for example.
1644 =item defined(%hash) is deprecated
1646 (D) defined() is not usually useful on hashes because it checks for an
1647 undefined I<scalar> value. If you want to see if the hash is empty,
1648 just use C<if (%hash) { # not empty }> for example.
1650 =item Did not produce a valid header
1654 =item Document contains no data
1658 =item entering effective %s failed
1660 (F) While under the C<use filetest> pragma, switching the real and
1661 effective uids or gids failed.
1663 =item false [] range "%s" in regexp
1665 (W) A character class range must start and end at a literal character, not
1666 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
1667 range is interpreted as a literal "-". Consider quoting the "-", "\-".
1670 =item Filehandle %s opened only for output
1672 (W) You tried to read from a filehandle opened only for writing. If you
1673 intended it to be a read/write filehandle, you needed to open it with
1674 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
1675 you intended only to read from the file, use "E<lt>". See
1678 =item Hexadecimal number > 0xffffffff non-portable
1680 (W) The hexadecimal number you specified is larger than 2**32-1
1681 (4294967295) and therefore non-portable between systems. See
1682 L<perlport> for more on portability concerns.
1684 =item Ill-formed CRTL environ value "%s"
1686 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
1687 environ array, and encountered an element without the C<=> delimiter
1688 used to spearate keys from values. The element is ignored.
1690 =item Ill-formed message in prime_env_iter: |%s|
1692 (W) A warning peculiar to VMS. Perl tried to read a logical name
1693 or CLI symbol definition when preparing to iterate over %ENV, and
1694 didn't see the expected delimiter between key and value, so the
1697 =item Illegal binary digit %s
1699 (F) You used a digit other than 0 or 1 in a binary number.
1701 =item Illegal binary digit %s ignored
1703 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
1704 Interpretation of the binary number stopped before the offending digit.
1706 =item Illegal number of bits in vec
1708 (F) The number of bits in vec() (the third argument) must be a power of
1709 two from 1 to 32 (or 64, if your platform supports that).
1711 =item Integer overflow in %s number
1713 (W) The hexadecimal, octal or binary number you have specified either
1714 as a literal or as an argument to hex() or oct() is too big for your
1715 architecture, and has been converted to a floating point number. On a
1716 32-bit architecture the largest hexadecimal, octal or binary number
1717 representable without overflow is 0xFFFFFFFF, 037777777777, or
1718 0b11111111111111111111111111111111 respectively. Note that Perl
1719 transparently promotes all numbers to a floating point representation
1720 internally--subject to loss of precision errors in subsequent
1723 =item Invalid %s attribute: %s
1725 The indicated attribute for a subroutine or variable was not recognized
1726 by Perl or by a user-supplied handler. See L<attributes>.
1728 =item Invalid %s attributes: %s
1730 The indicated attributes for a subroutine or variable were not recognized
1731 by Perl or by a user-supplied handler. See L<attributes>.
1733 =item invalid [] range "%s" in regexp
1735 The offending range is now explicitly displayed.
1737 =item Invalid separator character %s in attribute list
1739 (F) Something other than a comma or whitespace was seen between the
1740 elements of an attribute list. If the previous attribute
1741 had a parenthesised parameter list, perhaps that list was terminated
1742 too soon. See L<attributes>.
1744 =item Invalid separator character %s in subroutine attribute list
1746 (F) Something other than a comma or whitespace was seen between the
1747 elements of a subroutine attribute list. If the previous attribute
1748 had a parenthesised parameter list, perhaps that list was terminated
1751 =item leaving effective %s failed
1753 (F) While under the C<use filetest> pragma, switching the real and
1754 effective uids or gids failed.
1756 =item Lvalue subs returning %s not implemented yet
1758 (F) Due to limitations in the current implementation, array and hash
1759 values cannot be returned in subroutines used in lvalue context.
1760 See L<perlsub/"Lvalue subroutines">.
1762 =item Method %s not permitted
1766 =item Missing %sbrace%s on \N{}
1768 (F) Wrong syntax of character name literal C<\N{charname}> within
1769 double-quotish context.
1771 =item Missing command in piped open
1773 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
1774 construction, but the command was missing or blank.
1776 =item Missing name in "my sub"
1778 (F) The reserved syntax for lexically scoped subroutines requires that they
1779 have a name with which they can be found.
1781 =item no UTC offset information; assuming local time is UTC
1783 (S) A warning peculiar to VMS. Perl was unable to find the local
1784 timezone offset, so it's assuming that local system time is equivalent
1785 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
1786 to translate to the number of seconds which need to be added to UTC to
1789 =item Octal number > 037777777777 non-portable
1791 (W) The octal number you specified is larger than 2**32-1 (4294967295)
1792 and therefore non-portable between systems. See L<perlport> for more
1793 on portability concerns.
1795 See also L<perlport> for writing portable code.
1797 =item panic: del_backref
1799 (P) Failed an internal consistency check while trying to reset a weak
1802 =item panic: kid popen errno read
1804 (F) forked child returned an incomprehensible message about its errno.
1806 =item panic: magic_killbackrefs
1808 (P) Failed an internal consistency check while trying to reset all weak
1809 references to an object.
1811 =item Possible Y2K bug: %s
1813 (W) You are concatenating the number 19 with another number, which
1814 could be a potential Year 2000 problem.
1816 =item Premature end of script headers
1820 =item Repeat count in pack overflows
1822 (F) You can't specify a repeat count so large that it overflows
1823 your signed integers. See L<perlfunc/pack>.
1825 =item Repeat count in unpack overflows
1827 (F) You can't specify a repeat count so large that it overflows
1828 your signed integers. See L<perlfunc/unpack>.
1830 =item realloc() of freed memory ignored
1832 (S) An internal routine called realloc() on something that had already
1835 =item Reference is already weak
1837 (W) You have attempted to weaken a reference that is already weak.
1838 Doing so has no effect.
1840 =item setpgrp can't take arguments
1842 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
1843 unlike POSIX setpgid(), which takes a process ID and process group ID.
1845 =item Strange *+?{} on zero-length expression
1847 (W) You applied a regular expression quantifier in a place where it
1848 makes no sense, such as on a zero-width assertion.
1849 Try putting the quantifier inside the assertion instead. For example,
1850 the way to match "abc" provided that it is followed by three
1851 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
1853 =item switching effective %s is not implemented
1855 (F) While under the C<use filetest> pragma, we cannot switch the
1856 real and effective uids or gids.
1858 =item This Perl can't reset CRTL environ elements (%s)
1860 =item This Perl can't set CRTL environ elements (%s=%s)
1862 (W) Warnings peculiar to VMS. You tried to change or delete an element
1863 of the CRTL's internal environ array, but your copy of Perl wasn't
1864 built with a CRTL that contained the setenv() function. You'll need to
1865 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
1866 L<perlvms>) so that the environ array isn't the target of the change to
1867 %ENV which produced the warning.
1869 =item Unknown open() mode '%s'
1871 (F) The second argument of 3-argument open() is not among the list
1872 of valid modes: C<L<lt>>, C<L<gt>>, C<E<gt>E<gt>>, C<+L<lt>>,
1873 C<+L<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|->.
1875 =item Unknown process %x sent message to prime_env_iter: %s
1877 (P) An error peculiar to VMS. Perl was reading values for %ENV before
1878 iterating over it, and someone else stuck a message in the stream of
1879 data Perl expected. Someone's very confused, or perhaps trying to
1880 subvert Perl's population of %ENV for nefarious purposes.
1882 =item Unrecognized escape \\%c passed through
1884 (W) You used a backslash-character combination which is not recognized
1885 by Perl. The character was understood literally.
1887 =item Unterminated attribute parameter in attribute list
1889 (F) The lexer saw an opening (left) parenthesis character while parsing an
1890 attribute list, but the matching closing (right) parenthesis
1891 character was not found. You may need to add (or remove) a backslash
1892 character to get your parentheses to balance. See L<attributes>.
1894 =item Unterminated attribute list
1896 (F) The lexer found something other than a simple identifier at the start
1897 of an attribute, and it wasn't a semicolon or the start of a
1898 block. Perhaps you terminated the parameter list of the previous attribute
1899 too soon. See L<attributes>.
1901 =item Unterminated attribute parameter in subroutine attribute list
1903 (F) The lexer saw an opening (left) parenthesis character while parsing a
1904 subroutine attribute list, but the matching closing (right) parenthesis
1905 character was not found. You may need to add (or remove) a backslash
1906 character to get your parentheses to balance.
1908 =item Unterminated subroutine attribute list
1910 (F) The lexer found something other than a simple identifier at the start
1911 of a subroutine attribute, and it wasn't a semicolon or the start of a
1912 block. Perhaps you terminated the parameter list of the previous attribute
1915 =item Value of CLI symbol "%s" too long
1917 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
1918 element from a CLI symbol table, and found a resultant string longer
1919 than 1024 characters. The return value has been truncated to 1024
1922 =item Version number must be a constant number
1924 (P) The attempt to translate a C<use Module n.n LIST> statement into
1925 its equivalent C<BEGIN> block found an internal inconsistency with
1930 =head1 Obsolete Diagnostics
1934 =item Character class syntax [: :] is reserved for future extensions
1936 (W) Within regular expression character classes ([]) the syntax beginning
1937 with "[:" and ending with ":]" is reserved for future extensions.
1938 If you need to represent those character sequences inside a regular
1939 expression character class, just quote the square brackets with the
1940 backslash: "\[:" and ":\]".
1942 =item Ill-formed logical name |%s| in prime_env_iter
1944 (W) A warning peculiar to VMS. A logical name was encountered when preparing
1945 to iterate over %ENV which violates the syntactic rules governing logical
1946 names. Because it cannot be translated normally, it is skipped, and will not
1947 appear in %ENV. This may be a benign occurrence, as some software packages
1948 might directly modify logical name tables and introduce nonstandard names,
1949 or it may indicate that a logical name table has been corrupted.
1951 =item regexp too big
1953 (F) The current implementation of regular expressions uses shorts as
1954 address offsets within a string. Unfortunately this means that if
1955 the regular expression compiles to longer than 32767, it'll blow up.
1956 Usually when you want a regular expression this big, there is a better
1957 way to do it with multiple statements. See L<perlre>.
1959 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
1961 (D) Perl versions before 5.004 misinterpreted any type marker followed
1962 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
1963 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
1965 However, the developers of Perl 5.004 could not fix this bug completely,
1966 because at least two widely-used modules depend on the old meaning of
1967 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
1968 old (broken) way inside strings; but it generates this message as a
1969 warning. And in Perl 5.005, this special treatment will cease.
1975 If you find what you think is a bug, you might check the
1976 articles recently posted to the comp.lang.perl.misc newsgroup.
1977 There may also be information at http://www.perl.com/perl/, the Perl
1980 If you believe you have an unreported bug, please run the B<perlbug>
1981 program included with your release. Make sure to trim your bug down
1982 to a tiny but sufficient test case. Your bug report, along with the
1983 output of C<perl -V>, will be sent off to perlbug@perl.com to be
1984 analysed by the Perl porting team.
1988 The F<Changes> file for exhaustive details on what changed.
1990 The F<INSTALL> file for how to build Perl.
1992 The F<README> file for general stuff.
1994 The F<Artistic> and F<Copying> files for copyright information.
1998 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
1999 contributions from The Perl Porters.
2001 Send omissions or corrections to <F<perlbug@perl.com>>.