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
130 =head2 C Source Incompatibilities
134 =item C<PERL_POLLUTE>
136 Release 5.005 grandfathered old global symbol names by providing preprocessor
137 macros for extension source compatibility. As of release 5.6, these
138 preprocessor definitions are not available by default. You need to explicitly
139 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
140 extensions still using the old symbols, this option can be
141 specified via MakeMaker:
143 perl Makefile.PL POLLUTE=1
145 =item C<PERL_IMPLICIT_CONTEXT>
147 This new build option provides a set of macros for all API functions
148 such that an implicit interpreter/thread context argument is passed to
149 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
150 amounts to a macro invocation that actually translates to something like
151 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
152 to not have any significant source compatibility issues, the difference
153 between a macro and a real function call will need to be considered.
155 This means that there B<is> a source compatibility issue as a result of
156 this if your extensions attempt to use pointers to any of the Perl API
159 Note that the above issue is not relevant to the default build of
160 Perl, whose interfaces continue to match those of prior versions
161 (but subject to the other options described here).
163 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
164 with one of -Dusethreads, -Dusemultiplicity, or both.
166 See L<perlguts/"The Perl API"> for detailed information on the
167 ramifications of building Perl using this option.
169 =item C<PERL_POLLUTE_MALLOC>
171 Enabling Perl's malloc in release 5.005 and earlier caused
172 the namespace of system versions of the malloc family of functions to
173 be usurped by the Perl versions, since by default they used the
176 Besides causing problems on platforms that do not allow these functions to
177 be cleanly replaced, this also meant that the system versions could not
178 be called in programs that used Perl's malloc. Previous versions of Perl
179 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
180 EMBEDMYMALLOC preprocessor definitions.
182 As of release 5.6, Perl's malloc family of functions have default names
183 distinct from the system versions. You need to explicitly compile perl with
184 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
185 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
188 Note that these functions do B<not> constitute Perl's memory allocation API.
189 See L<perlguts/"Memory Allocation"> for further information about that.
193 =head2 Compatible C Source API Changes
197 =item C<PATCHLEVEL> is now C<PERL_VERSION>
199 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
200 are now available by default from perl.h, and reflect the base revision,
201 patchlevel, and subversion respectively. C<PERL_REVISION> had no
202 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
203 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
205 The new names cause less pollution of the B<cpp> namespace and reflect what
206 the numbers have come to stand for in common practice. For compatibility,
207 the old names are still supported when F<patchlevel.h> is explicitly
208 included (as required before), so there is no source incompatibility
211 =item Support for C++ exceptions
213 change#3386, also needs perlguts documentation
214 [TODO - Chip Salzenberg <chip@perlsupport.com>]
218 =head2 Binary Incompatibilities
220 The default build of this release is binary compatible with the 5.005
221 release or its maintenance versions.
223 The usethreads or usemultiplicity builds are B<not> binary compatible
224 with the corresponding builds in 5.005.
226 =head1 Installation and Configuration Improvements
228 =head2 New Configure flags
230 The following new flags may be enabled on the Configure command line
231 by running Configure with C<-Dflag>.
239 =head2 -Dusethreads and -Duse64bits now more daring
241 The Configure options enabling the use of threads and the use of
242 64-bitness are now more daring in the sense that they no more have
243 an explicit list of operating systems of known threads/64-bit
244 capabilities. In other words: if your operating system has the
245 necessary APIs, you should be able just to go ahead and use them.
246 See also L<"64-bit support">.
250 Some platforms have "long doubles", floating point numbers of even
251 larger range than ordinary "doubles". To enable using long doubles for
252 Perl's scalars, use -Duselongdouble.
256 You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
257 See also L<"64-bit support">.
259 =head2 -Duselargefiles
261 Some platforms support large files, files larger than two gigabytes.
262 See L<"Large file support"> for more information.
264 =head2 installusrbinperl
266 You can use "Configure -Uinstallusrbinperl" which causes installperl
267 to skip installing perl also as /usr/bin/perl. This is useful if you
268 prefer not to modify /usr/bin for some reason or another but harmful
269 because many scripts assume to find Perl in /usr/bin/perl.
273 You can use "Configure -Dusesocks" which causes Perl to probe
274 for the SOCKS (v5, not v4) proxy protocol library,
275 http://www.socks.nec.com/
279 You can "post-edit" the Configure variables using the Configure C<-A>
280 flag. The editing happens immediately after the platform specific
281 hints files have been processed but before the actual configuration
282 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
284 =head2 Enhanced Installation Directories
286 The installation structure has been enriched to improve the support for
287 maintaining multiple versions of perl, to provide locations for
288 vendor-supplied modules and scripts, and to ease maintenance of
289 locally-added modules and scripts. See the section on Installation
290 Directories in the INSTALL file for complete details. For most users
291 building and installing from source, the defaults should be fine.
295 =head2 Unicode and UTF-8 support
297 Perl can optionally use UTF-8 as its internal representation for character
298 strings. The C<utf8> pragma enables this support in the current lexical
299 scope. See L<utf8> for more information.
301 =head2 Lexically scoped warning categories
303 You can now control the granularity of warnings emitted by perl at a finer
304 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
307 =head2 Lvalue subroutines
309 WARNING: This is an experimental feature.
312 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
313 Tuomas Lukka <lukka@fas.harvard.edu>)]
315 =head2 "our" declarations
317 An "our" declaration introduces a value that can be best understood
318 as a lexically scoped symbolic alias to a global variable in the
319 current package. This is mostly useful as an alternative to the
320 C<vars> pragma, but also provides the opportunity to introduce
321 typing and other attributes for such variables. See L<perlfunc/our>.
323 =head2 Weak references
325 WARNING: This is an experimental feature.
327 change#3385, also need perlguts documentation
329 [TODO - Tuomas Lukka <lukka@fas.harvard.edu>]
331 =head2 File globbing implemented internally
333 WARNING: This is currently an experimental feature. Interfaces and
334 implementation are likely to change.
336 Perl can be compiled with -DPERL_INTERNAL_GLOB to use the File::Glob
337 implementation of the glob() operator. This avoids using an external
338 csh process and the problems associated with it.
340 =head2 Binary numbers supported
342 Binary numbers are now supported as literals, in s?printf formats, and
346 printf "The answer is: %b\n", oct("0b101010");
348 =head2 Some arrows may be omitted in calls through references
350 Perl now allows the arrow to be omitted in many constructs
351 involving subroutine calls through references. For example,
352 C<$foo[10]->('foo')> may now be written C<$foo[10]('foo')>.
353 This is rather similar to how the arrow may be omitted from
354 C<$foo[10]->{'foo'}>. Note however, that the arrow is still
355 required for C<foo(10)->('bar')>.
357 =head2 syswrite() ease-of-use
359 The length argument of C<syswrite()> has become optional.
361 =head2 Filehandles can be autovivified
363 The construct C<open(my $fh, ...)> can be used to create filehandles
364 more easily. The filehandle will be automatically closed at the end
365 of the scope of $fh, provided there are no other references to it. This
366 largely eliminates the need for typeglobs when opening filehandles
367 that must be passed around, as in the following example:
371 or die "Can't open '@_': $!";
376 my $f = myopen("</etc/motd");
378 # $f implicitly closed here
381 [TODO - this idiom needs more pod penetration]
383 =head2 64-bit support
385 All platforms that have 64-bit integers either (a) natively as longs
386 or ints (b) via special compiler flags (c) using long long are able to
387 use "quads" (64-integers) as follows:
393 constants (decimal, hexadecimal, octal, binary) in the code
397 arguments to oct() and hex()
401 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
409 pack() and unpack() "q" and "Q" formats
413 in basic arithmetics: + - * / %
417 vec() (but see the below note about bit arithmetics)
421 Note that unless you have the case (a) you will have to configure
422 and compile Perl using the -Duse64bits Configure flag.
424 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
425 64-bit clean, they are explictly forced to be 32-bit. Bit arithmetics
426 for bit vectors (created by vec()) are not limited in their width.
428 Last but not least: note that due to Perl's habit of always using
429 floating point numbers the quads are still not true integers.
430 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
431 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
432 are silently promoted to floating point numbers, after which they will
433 start losing precision (their lower digits).
435 =head2 Large file support
437 If you have filesystems that support "large files" (files larger than
438 2 gigabytes), you may now also be able to create and access them from
439 Perl. You have to use Configure -Duselargefiles. Turning on the
440 large file support turns on also the 64-bit support, for obvious reasons.
442 Note that in addition to requiring a proper file system to do large
443 files you may also need to adjust your per-process (or your
444 per-system, or per-process-group, or per-user-group) maximum filesize
445 limits before running Perl scripts that try to handle large files,
446 especially if you intend to write such files.
448 Finally, in addition to your process/process group maximum filesize
449 limits, you may have quota limits on your filesystems that stop you
450 (your user id or your user group id) from using large files.
452 Adjusting your process/user/group/file system/operating system limits
453 is outside the scope of Perl core language. For process limits, you
454 may try increasing the limits using your shell's limits/limit/ulimit
455 command before running Perl. The BSD::Resource extension (not
456 included with the standard Perl distribution) may also be of use, it
457 offers the getrlimit/setrlimit interface that can be used to adjust
458 process resource usage limits, including the maximum filesize limit.
462 In some systems you may be able to use long doubles to enhance the
463 range of precision of your double precision floating point numbers
464 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
465 this support (if it is available).
469 You can Configure -Dusemorebits to turn on both the 64-bit support
470 and the long double support.
472 =head2 Better syntax checks on parenthesized unary operators
476 print defined(&foo,&bar,&baz);
477 print uc("foo","bar","baz");
480 used to be accidentally allowed in earlier versions, and produced
481 unpredictable behaviour. Some produced ancillary warnings
482 when used in this way; others silently did the wrong thing.
484 The parenthesized forms of most unary operators that expect a single
485 argument now ensure that they are not called with more than one
486 argument, making the cases shown above syntax errors. The usual
489 print defined &foo, &bar, &baz;
490 print uc "foo", "bar", "baz";
493 remains unchanged. See L<perlop>.
495 =head2 POSIX character class syntax [: :] supported
497 For example to match alphabetic characters use /[[:alpha:]]/.
498 See L<perlre> for details.
500 =head2 Improved C<qw//> operator
502 The C<qw//> operator is now evaluated at compile time into a true list
503 instead of being replaced with a run time call to C<split()>. This
504 removes the confusing misbehaviour of C<qw//> in scalar context, which
505 had inherited that behaviour from split().
509 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
511 now correctly prints "3|a", instead of "2|a".
513 =head2 pack() format 'Z' supported
515 The new format type 'Z' is useful for packing and unpacking null-terminated
516 strings. See L<perlfunc/"pack">.
518 =head2 pack() format modifier '!' supported
520 The new format type modifier '!' is useful for packing and unpacking
521 native shorts, ints, and longs. See L<perlfunc/"pack">.
523 =head2 pack() and unpack() support counted strings
525 The template character '/' can be used to specify a counted string
526 type to be packed or unpacked. See L<perlfunc/"pack">.
528 =head2 Comments in pack() templates
530 The '#' character in a template introduces a comment up to
531 end of the line. This facilitates documentation of pack()
534 =head2 $^X variables may now have names longer than one character
536 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
537 error. Now variable names that begin with a control character may be
538 arbitrarily long. However, for compatibility reasons, these variables
539 I<must> be written with explicit braces, as C<${^XY}> for example.
540 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
541 than one control character, such as C<${^XY^Z}>, are illegal.
543 The old syntax has not changed. As before, `^X' may be either a
544 literal control-X character or the two-character sequence `caret' plus
545 `X'. When braces are omitted, the variable name stops after the
546 control character. Thus C<"$^XYZ"> continues to be synonymous with
547 C<$^X . "YZ"> as before.
549 As before, lexical variables may not have names beginning with control
550 characters. As before, variables whose names begin with a control
551 character are always forced to be in package `main'. All such variables
552 are reserved for future extensions, except those that begin with
553 C<^_>, which may be used by user programs and are guaranteed not to
554 acquire special meaning in any future version of Perl.
556 =head2 C<use attrs> implicit in subroutine attributes
558 Formerly, if you wanted to mark a subroutine as being a method call or
559 as requiring an automatic lock() when it is entered, you had to declare
560 that with a C<use attrs> pragma in the body of the subroutine.
561 That can now be accomplished with a declaration syntax, like this:
563 sub mymethod : locked, method ;
565 sub mymethod : locked, method {
569 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
570 with the stubs they provide. See L<attributes>.
572 =head2 Regular expression improvements
574 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
575 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
577 =head2 Overloading improvements
580 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
582 =head2 open() with more than two arguments
584 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
586 =head2 Support for interpolating named characters
589 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
591 =head2 Experimental support for user-hooks in @INC
593 [TODO - Ken Fox <kfox@ford.com>]
595 =head2 C<require> and C<do> may be overridden
597 C<require> and C<do 'file'> operations may be overridden locally
598 by importing subroutines of the same name into the current package
599 (or globally by importing them into the CORE::GLOBAL:: namespace).
600 Overriding C<require> will also affect C<use>, provided the override
601 is visible at compile-time.
602 See L<perlsub/"Overriding Built-in Functions">.
604 =head2 New variable $^C reflects C<-c> switch
606 C<$^C> has a boolean value that reflects whether perl is being run
607 in compile-only mode (i.e. via the C<-c> switch). Since
608 BEGIN blocks are executed under such conditions, this variable
609 enables perl code to determine whether actions that make sense
610 only during normal running are warranted. See L<perlvar>.
614 Arbitrary code can be queued for execution when Perl has finished
615 parsing the program (i.e. when the compile phase ends) using STOP
616 blocks. These behave similar to END blocks, except for being
617 called at the end of compilation rather than at the end of execution.
619 =head2 Optional Y2K warnings
621 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
622 it emits optional warnings when concatenating the number 19
625 This behavior must be specifically enabled when running Configure.
626 See L<INSTALL> and L<README.Y2K>.
628 =head1 Significant bug fixes
630 =head2 E<lt>HANDLEE<gt> on empty files
632 With C<$/> set to C<undef>, slurping an empty file returns a string of
633 zero length (instead of C<undef>, as it used to) the first time the
634 HANDLE is read. Further reads yield C<undef>.
636 This means that the following will append "foo" to an empty file (it used
639 perl -0777 -pi -e 's/^/foo/' empty_file
643 perl -pi -e 's/^/foo/' empty_file
645 is unchanged (it continues to leave the file empty).
647 =head2 C<eval '...'> improvements
649 Line numbers (as reflected by caller() and most diagnostics) within
650 C<eval '...'> were often incorrect when here documents were involved.
651 This has been corrected.
653 Lexical lookups for variables appearing in C<eval '...'> within
654 functions that were themselves called within an C<eval '...'> were
655 searching the wrong place for lexicals. The lexical search now
656 correctly ends at the subroutine's block boundary.
658 Parsing of here documents used to be flawed when they appeared as
659 the replacement expression in C<eval 's/.../.../e'>. This has
662 =head2 All compilation errors are true errors
664 Some "errors" encountered at compile time were by neccessity
665 generated as warnings followed by eventual termination of the
666 program. This enabled more such errors to be reported in a
667 single run, rather than causing a hard stop at the first error
668 that was encountered.
670 The mechanism for reporting such errors has been reimplemented
671 to queue compile-time errors and report them at the end of the
672 compilation as true errors rather than as warnings. This fixes
673 cases where error messages leaked through in the form of warnings
674 when code was compiled at run time using C<eval STRING>, and
675 also allows such errors to be reliably trapped using __DIE__ hooks.
677 =head2 Automatic flushing of output buffers
679 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
680 of all files opened for output when the operation
681 was attempted. This mostly eliminates confusing
682 buffering mishaps suffered by users unaware of how Perl internally
685 =head2 Better diagnostics on meaningless filehandle operations
687 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
688 are compile time errors. Attempting to read from filehandles that
689 were opened only for writing will now produce warnings (just as
690 writing to read-only filehandles does).
692 =head2 Where possible, buffered data discarded from duped input filehandle
694 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
695 was previously read and buffered in C<OLD> before duping the handle.
696 On platforms where doing this is allowed, the next read operation
697 on C<NEW> will return the same data as the corresponding operation
698 on C<OLD>. Formerly, it would have returned the data from the start
699 of the following disk block instead.
701 =head2 system(), backticks and pipe open now reflect exec() failure
703 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
704 etc., are implemented via fork() and exec(). When the underlying
705 exec() fails, earlier versions did not report the error properly,
706 since the exec() happened to be in a different process.
708 The child process now communicates with the parent about the
709 error in launching the external command, which allows these
710 constructs to return with their usual error value and set $!.
712 =head2 Implicitly closed filehandles are safer
714 Sometimes implicitly closed filehandles (as when they are localized,
715 and Perl automatically closes them on exiting the scope) could
716 inadvertently set $? or $!. This has been corrected.
718 =head2 C<(\$)> prototype and C<$foo{a}>
720 An scalar reference prototype now correctly allows a hash or
721 array element in that slot.
723 =head2 Pseudo-hashes work better
725 Dereferencing some types of reference values in a pseudo-hash,
726 such as C<$ph->{foo}[1]>, was accidentally disallowed. This has
729 When applied to a pseudo-hash element, exists() now reports whether
730 the specified value exists, not merely if the key is valid.
732 =head2 C<goto &sub> and AUTOLOAD
734 The C<goto &sub> construct works correctly when C<&sub> happens
737 =head2 C<-bareword> allowed under C<use integer>
739 The autoquoting of barewords preceded by C<-> did not work
740 in prior versions when the C<integer> pragma was enabled.
743 =head2 Boolean assignment operators are legal lvalues
745 Constructs such as C<($a ||= 2) += 1> are now allowed.
747 =head2 C<sort $coderef @foo> allowed
749 sort() did not accept a subroutine reference as the comparison
750 function in earlier versions. This is now permitted.
752 =head2 Failures in DESTROY()
754 When code in a destructor threw an exception, it went unnoticed
755 in earlier versions of Perl, unless someone happened to be
756 looking in $@ just after the point the destructor happened to
757 run. Such failures are now visible as warnings when warnings are
760 =head2 Locale bugs fixed
762 printf() and sprintf() previously reset the numeric locale
763 back to the default "C" locale. This has been fixed.
765 Numbers formatted according to the local numeric locale
766 (such as using a decimal comma instead of a decimal dot) caused
767 "isn't numeric" warnings, even while the operations accessing
768 those numbers produced correct results. The warnings are gone.
772 The C<eval 'return sub {...}'> construct could sometimes leak
773 memory. This has been fixed.
775 Operations that aren't filehandle constructors used to leak memory
776 when used on invalid filehandles. This has been fixed.
778 Constructs that modified C<@_> could fail to deallocate values
779 in C<@_> and thus leak memory. This has been corrected.
781 =head2 Spurious subroutine stubs after failed subroutine calls
783 Perl could sometimes create empty subroutine stubs when a
784 subroutine was not found in the package. Such cases stopped
785 later method lookups from progressing into base packages.
786 This has been corrected.
788 =head2 Consistent numeric conversions
791 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
793 =head2 Taint failures under C<-U>
795 When running in unsafe mode, taint violations could sometimes
796 cause silent failures. This has been fixed.
798 =head2 END blocks and the C<-c> switch
800 Prior versions used to run BEGIN B<and> END blocks when Perl was
801 run in compile-only mode. Since this is typically not the expected
802 behavior, END blocks are not executed anymore when the C<-c> switch
805 See L<STOP blocks> for how to run things when the compile phase ends.
807 =head2 Potential to leak DATA filehandles
809 Using the C<__DATA__> token creates an implicit filehandle to
810 the file that contains the token. It is the program's
811 responsibility to close it when it is done reading from it.
813 This caveat is now better explained in the documentation.
816 =head2 Diagnostics follow STDERR
818 Diagnostic output now goes to whichever file the C<STDERR> handle
819 is pointing at, instead of always going to the underlying C runtime
822 =head2 Other fixes for better diagnostics
824 Line numbers are no longer suppressed (under most likely circumstances)
825 during the global destruction phase.
827 Diagnostics emitted from code running in threads other than the main
828 thread are now accompanied by the thread ID.
830 Embedded null characters in diagnostics now actually show up. They
831 used to truncate the message in prior versions.
833 $foo::a and $foo::b are now exempt from "possible typo" warnings only
834 if sort() is encountered in package foo.
836 Unrecognized alphabetic escapes encountered when parsing quote
837 constructs now generate a warning, since they may take on new
838 semantics in later versions of Perl.
840 =head1 Performance enhancements
842 =head2 Simple sort() using { $a <=> $b } and the like are optimized
844 Many common sort() operations using a simple inlined block are now
845 optimized for faster performance.
847 =head2 Optimized assignments to lexical variables
849 Certain operations in the RHS of assignment statements have been
850 optimized to directly set the lexical variable on the LHS,
851 eliminating redundant copying overheads.
853 =head2 Method lookups optimized
855 [TODO - Chip Salzenberg <chip@perlsupport.com>]
857 =head2 Faster mechanism to invoke XSUBs
860 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
862 =head2 Perl_malloc() improvements
865 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
867 =head2 Faster subroutine calls
869 Minor changes in how subroutine calls are handled internally
870 provide marginal improvements in performance.
872 =head1 Platform specific changes
874 =head2 Additional supported platforms
880 VM/ESA is now supported.
884 Siemens BS2000 is now supported under the POSIX Shell.
888 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
893 GNU/Hurd is now supported.
897 Rhapsody is now supported.
901 EPOC is is now supported (on Psion 5).
911 Perl now works with djgpp 2.02 (and 2.03 alpha).
915 Environment variable names are not converted to uppercase any more.
919 Wrong exit code from backticks now fixed.
923 This port is still using its own builtin globbing.
929 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
933 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
937 Site library searches failed to look for ".../site/5.XXX/lib"
938 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
940 When given a pathname that consists only of a drivename, such
941 as C<A:>, opendir() and stat() now use the current working
942 directory for the drive rather than the drive root.
944 The builtin XSUB functions in the Win32:: namespace are
945 documented. See L<Win32>.
947 $^X now contains the full path name of the running executable.
949 A Win32::GetLongPathName() function is provided to complement
950 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
952 POSIX::uname() is supported.
954 system(1,...) now returns true process IDs rather than process
955 handles. kill() accepts any real process id, rather than strictly
956 return values from system(1,...).
958 The C<Shell> module is supported.
960 Rudimentary support for building under command.com in Windows 95
971 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
975 IO constants (SEEK_*, _IO*).
979 Directory-related IO methods (new, read, close, rewind, tied delete).
981 =item lib/io_multihomed
983 INET sockets with multi-homed hosts.
995 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1003 Verify operations that access pad objects (lexicals and temporaries).
1007 =head1 Modules and Pragmata
1015 While used internally by Perl as a pragma, this module also
1016 provides a way to fetch subroutine and variable attributes.
1021 The Perl Compiler suite has been extensively reworked for this
1024 [TODO - Vishal Bhatia <vishal@gol.com>,
1025 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1029 The ByteLoader is a dedicated extension to generate and run
1030 Perl bytecode. See L<ByteLoader>.
1034 References can now be used. See L<constant>.
1039 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1043 A C<Maxdepth> setting can be specified to avoid venturing
1044 too deeply into deep data structures. See L<Data::Dumper>.
1046 Dumping C<qr//> objects works correctly.
1050 C<DB> is an experimental module that exposes a clean abstraction
1051 to Perl's debugging API.
1055 [TODO - Paul Marquess <paul.marquess@bt.com>]
1059 Devel::DProf, a Perl source code profiler has been added. See
1060 L<Devel::DProf> and L<dprofpp>.
1064 The Dumpvalue module provides screen dumps of Perl data.
1068 Overall, Benchmark results exhibit lower average error and better timing
1071 You can now run tests for I<n> seconds instead of guessing the right
1072 number of tests to run: e.g. timethese(-5, ...) will run each
1073 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1074 means "for at least 3 CPU seconds". The output format has also
1075 changed. For example:
1077 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1079 will now output something like this:
1081 Benchmark: running a, b, each for at least 5 CPU seconds...
1082 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1083 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1085 New features: "each for at least N CPU seconds...", "wallclock secs",
1086 and the "@ operations/CPU second (n=operations)".
1088 timethese() now returns a reference to a hash of Benchmark objects containing
1089 the test results, keyed on the names of the tests.
1091 timethis() now returns the iterations field in the Benchmark result object
1094 timethese(), timethis(), and the new cmpthese() (see below) can also take
1095 a format specifier of 'none' to suppress output.
1097 A new function countit() is just like timeit() except that it takes a
1098 TIME instead of a COUNT.
1100 A new function cmpthese() prints a chart comparing the results of each test
1101 returned from a timethese() call. For each possible pair of tests, the
1102 percentage speed difference (iters/sec or seconds/iter) is shown.
1104 For other details, see L<Benchmark>.
1108 The Devel::Peek module provides access to the internal representation
1109 of Perl variables and data. It is a data debugging tool for the XS programmer.
1111 =item ExtUtils::MakeMaker
1113 change#4135, also needs docs in module pod
1114 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1118 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1119 large (more than 4G) file access (64-bit support is not yet
1120 working, though, so no need to get overly excited), Free/Net/OpenBSD
1121 locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
1122 O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
1126 A compare_text() function has been added, which allows custom
1127 comparison functions. See L<File::Compare>.
1131 File::Find now works correctly when the wanted() function is either
1132 autoloaded or is a symbolic reference.
1134 A bug that caused File::Find to lose track of the working directory
1135 when pruning top-level directories has been fixed.
1139 This extension implements BSD-style file globbing. It will also be
1140 used for the internal implementation of the glob() operator if
1141 Perl was compiled with -DPERL_INTERNAL_GLOB. See L<File::Glob>.
1145 New methods have been added to the File::Spec module: devnull() returns
1146 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1147 the temp directory (normally /tmp on Unix). There are now also methods
1148 to convert between absolute and relative filenames: abs2rel() and
1149 rel2abs(). For compatibility with operating systems that specify volume
1150 names in file paths, the splitpath(), splitdir(), and catdir() methods
1153 =item File::Spec::Functions
1155 The new File::Spec::Functions modules provides a function interface
1156 to the File::Spec module. Allows shorthand
1158 $fullname = catfile($dir1, $dir2, $file);
1162 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1166 Getopt::Long licensing has changed to allow the Perl Artistic License
1167 as well as the GPL. It used to be GPL only, which got in the way of
1168 non-GPL applications that wanted to use Getopt::Long.
1170 Getopt::Long encourages the use of Pod::Usage to produce help
1171 messages. For example:
1177 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1178 pod2usage(1) if $help;
1179 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1185 sample - Using GetOpt::Long and Pod::Usage
1189 sample [options] [file ...]
1192 -help brief help message
1193 -man full documentation
1201 Print a brief help message and exits.
1205 Prints the manual page and exits.
1211 B<This program> will read the given input file(s) and do someting
1212 useful with the contents thereof.
1216 See L<Pod::Usage> for details.
1218 A bug that prevented the non-option call-back E<lt>E<gt> from being
1219 specified as the first argument has been fixed.
1221 To specify the characters E<lt> and E<gt> as option starters, use
1222 E<gt>E<lt>. Note, however, that changing option starters is strongly
1227 write() and syswrite() will now accept a single-argument
1228 form of the call, for consistency with Perl's syswrite().
1230 You can now create a TCP-based IO::Socket::INET without forcing
1231 a connect attempt. This allows you to configure its options
1232 (like making it non-blocking) and then call connect() manually.
1234 A bug that prevented the IO::Socket::protocol() accessor
1235 from ever returning the correct value has been corrected.
1239 Java Perl Lingo is now distributed with Perl. See jpl/README
1240 for more information.
1244 C<use lib> now weeds out any trailing duplicate entries.
1245 C<no lib> removes all named entries.
1249 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1250 and C<~> are now supported on bigints.
1254 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1255 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1259 A little bit of radial trigonometry (cylindrical and spherical),
1260 radial coordinate conversions, and the great circle distance were added.
1264 [TODO - Brad Appleton <bradapp@enteract.com>]
1266 =item Pod::Text and Pod::Man
1268 [TODO - Russ Allbery <rra@stanford.edu>]
1272 An EXISTS method has been added to this module (and sdbm_exists() has
1273 been added to the underlying sdbm library), so one can now call exists
1274 on an SDBM_File tied hash and get the correct result, rather than a
1277 A bug that may have caused data loss when more than one disk block
1278 happens to be read from the database in a single FETCH() has been
1283 The timelocal() and timegm() functions used to silently return bogus
1284 results when the date fell outside the machine's integer range. They
1285 now consistently croak() if the date falls in an unsupported range.
1289 The error return value in list context has been changed for all functions
1290 that return a list of values. Previously these functions returned a list
1291 with a single element C<undef> if an error occurred. Now these functions
1292 return the empty list in these situations. This applies to the following
1298 The remaining functions are unchanged and continue to return C<undef> on
1299 error even in list context.
1301 The Win32::SetLastError(ERROR) function has been added as a complement
1302 to the Win32::GetLastError() function.
1304 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1305 pathname for FILENAME in scalar context. In list context it returns
1306 a two-element list containing the fully qualified directory name and
1307 the filename. See L<Win32>.
1311 A new feature called "DBM Filters" has been added to all the
1312 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1313 DBM Filters add four new methods to each DBM module:
1320 These can be used to filter key-value pairs before the pairs are
1321 written to the database or just after they are read from the database.
1322 See L<perldbmfilter> for further information.
1328 C<use attrs> is now obsolete, and is only provided for
1329 backward-compatibility. It's been replaced by the C<sub : attributes>
1330 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1332 C<use utf8> to enable UTF-8 and Unicode support.
1334 C<use caller 'encoding'> allows modules to inherit pragmatic attributes
1335 from the caller's context. C<encoding> is currently the only supported
1338 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1341 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1342 ...). Currently only one subpragma implemented, "use filetest
1343 'access';", that uses access(2) or equivalent to check permissions
1344 instead of using stat(2) as usual. This matters in filesystems
1345 where there are ACLs (access control lists): the stat(2) might lie,
1346 but access(2) knows better.
1348 =head1 Utility Changes
1352 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1356 C<perlcc> now supports the C and Bytecode backends. By default,
1357 it generates output from the simple C backend rather than the
1358 optimized C backend.
1360 Support for non-Unix platforms has been improved.
1365 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1367 =head1 Documentation Changes
1371 =item perlcompile.pod
1373 An introduction to using the Perl Compiler suite.
1375 =item perlfilter.pod
1377 An introduction to writing Perl source filters.
1381 Some guidelines for hacking the Perl source code.
1383 =item perlopentut.pod
1385 A tutorial on using open() effectively.
1387 =item perlreftut.pod
1389 A tutorial that introduces the essentials of references.
1393 A tutorial on managing class data for object modules.
1397 =head1 New or Changed Diagnostics
1401 =item "my sub" not yet implemented
1403 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1406 =item '!' allowed only after types %s
1408 (F) The '!' is allowed in pack() and unpack() only after certain types.
1409 See L<perlfunc/pack>.
1411 =item / cannot take a count
1413 (F) You had an unpack template indicating a counted-length string,
1414 but you have also specified an explicit size for the string.
1415 See L<perlfunc/pack>.
1417 =item / must be followed by a, A or Z
1419 (F) You had an unpack template indicating a counted-length string,
1420 which must be followed by one of the letters a, A or Z
1421 to indicate what sort of string is to be unpacked.
1422 See L<perlfunc/pack>.
1424 =item / must be followed by a*, A* or Z*
1426 (F) You had a pack template indicating a counted-length string,
1427 Currently the only things that can have their length counted are a*, A* or Z*.
1428 See L<perlfunc/pack>.
1430 =item / must follow a numeric type
1432 (F) You had an unpack template that contained a '#',
1433 but this did not follow some numeric unpack specification.
1434 See L<perlfunc/pack>.
1436 =item /%s/: Unrecognized escape \\%c passed through
1438 (W) You used a backslash-character combination which is not recognized
1439 by Perl. This combination appears in an interpolated variable or a
1440 C<'>-delimited regular expression. The character was understood literally.
1442 =item /%s/: Unrecognized escape \\%c in character class passed through
1444 (W) You used a backslash-character combination which is not recognized
1445 by Perl inside character classes. The character was understood literally.
1447 =item /%s/ should probably be written as "%s"
1449 (W) You have used a pattern where Perl expected to find a string,
1450 as in the first argument to C<join>. Perl will treat the true
1451 or false result of matching the pattern against $_ as the string,
1452 which is probably not what you had in mind.
1454 =item %s() called too early to check prototype
1456 (W) You've called a function that has a prototype before the parser saw a
1457 definition or declaration for it, and Perl could not check that the call
1458 conforms to the prototype. You need to either add an early prototype
1459 declaration for the subroutine in question, or move the subroutine
1460 definition ahead of the call to get proper prototype checking. Alternatively,
1461 if you are certain that you're calling the function correctly, you may put
1462 an ampersand before the name to avoid the warning. See L<perlsub>.
1464 =item %s package attribute may clash with future reserved word: %s
1466 (W) A lowercase attribute name was used that had a package-specific handler.
1467 That name might have a meaning to Perl itself some day, even though it
1468 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1471 =item (in cleanup) %s
1473 (W) This prefix usually indicates that a DESTROY() method raised
1474 the indicated exception. Since destructors are usually called by
1475 the system at arbitrary points during execution, and often a vast
1476 number of times, the warning is issued only once for any number
1477 of failures that would otherwise result in the same message being
1480 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1481 could also result in this warning. See L<perlcall/G_KEEPERR>.
1483 =item <> should be quotes
1485 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1488 =item Attempt to join self
1490 (F) You tried to join a thread from within itself, which is an
1491 impossible task. You may be joining the wrong thread, or you may
1492 need to move the join() to some other thread.
1494 =item Bad evalled substitution pattern
1496 (F) You've used the /e switch to evaluate the replacement for a
1497 substitution, but perl found a syntax error in the code to evaluate,
1498 most likely an unexpected right brace '}'.
1500 =item Bad realloc() ignored
1502 (S) An internal routine called realloc() on something that had never been
1503 malloc()ed in the first place. Mandatory, but can be disabled by
1504 setting environment variable C<PERL_BADFREE> to 1.
1506 =item Binary number > 0b11111111111111111111111111111111 non-portable
1508 (W) The binary number you specified is larger than 2**32-1
1509 (4294967295) and therefore non-portable between systems. See
1510 L<perlport> for more on portability concerns.
1512 =item Bit vector size > 32 non-portable
1514 (W) Using bit vector sizes larger than 32 is non-portable.
1516 =item Buffer overflow in prime_env_iter: %s
1518 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
1519 %ENV, it encountered a logical name or symbol definition which was too long,
1520 so it was truncated to the string shown.
1522 =item Can't check filesystem of script "%s"
1524 (P) For some reason you can't check the filesystem of the script for nosuid.
1526 =item Can't ignore signal CHLD, forcing to default
1528 (W) Perl has detected that it is being run with the SIGCHLD signal
1529 (sometimes known as SIGCLD) disabled. Since disabling this signal
1530 will interfere with proper determination of exit status of child
1531 processes, Perl has reset the signal to its default value.
1532 This situation typically indicates that the parent program under
1533 which Perl may be running (e.g. cron) is being very careless.
1535 =item Can't modify non-lvalue subroutine call
1537 (F) Subroutines meant to be used in lvalue context should be declared as
1538 such, see L<perlsub/"Lvalue subroutines">.
1540 =item Can't read CRTL environ
1542 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1543 from the CRTL's internal environment array and discovered the array was
1544 missing. You need to figure out where your CRTL misplaced its environ
1545 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1547 =item Can't remove %s: %s, skipping file
1549 (S) You requested an inplace edit without creating a backup file. Perl
1550 was unable to remove the original file to replace it with the modified
1551 file. The file was left unmodified.
1553 =item Can't return %s from lvalue subroutine
1555 (F) Perl detected an attempt to return illegal lvalues (such
1556 as temporary or readonly values) from a subroutine used as an lvalue.
1557 This is not allowed.
1559 =item Can't weaken a nonreference
1561 (F) You attempted to weaken something that was not a reference. Only
1562 references can be weakened.
1564 =item Character class [:%s:] unknown
1566 (F) The class in the character class [: :] syntax is unknown.
1569 =item Character class syntax [%s] belongs inside character classes
1571 (W) The character class constructs [: :], [= =], and [. .] go
1572 I<inside> character classes, the [] are part of the construct,
1573 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1574 are not currently implemented; they are simply placeholders for
1577 =item Constant is not %s reference
1579 (F) A constant value (perhaps declared using the C<use constant> pragma)
1580 is being dereferenced, but it amounts to the wrong type of reference. The
1581 message indicates the type of reference that was expected. This usually
1582 indicates a syntax error in dereferencing the constant value.
1583 See L<perlsub/"Constant Functions"> and L<constant>.
1585 =item constant(%s): %%^H is not localized
1587 (F) When setting compile-time-lexicalized hash %^H one should set the
1588 corresponding bit of $^H as well.
1590 =item constant(%s): %s
1592 (F) Compile-time-substitutions (such as overloaded constants and
1593 character names) were not correctly set up.
1595 =item defined(@array) is deprecated
1597 (D) defined() is not usually useful on arrays because it checks for an
1598 undefined I<scalar> value. If you want to see if the array is empty,
1599 just use C<if (@array) { # not empty }> for example.
1601 =item defined(%hash) is deprecated
1603 (D) defined() is not usually useful on hashes because it checks for an
1604 undefined I<scalar> value. If you want to see if the hash is empty,
1605 just use C<if (%hash) { # not empty }> for example.
1607 =item Did not produce a valid header
1611 =item Document contains no data
1615 =item entering effective %s failed
1617 (F) While under the C<use filetest> pragma, switching the real and
1618 effective uids or gids failed.
1620 =item false [] range "%s" in regexp
1622 (W) A character class range must start and end at a literal character, not
1623 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
1624 range is interpreted as a literal "-". Consider quoting the "-", "\-".
1627 =item Filehandle %s opened only for output
1629 (W) You tried to read from a filehandle opened only for writing. If you
1630 intended it to be a read/write filehandle, you needed to open it with
1631 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
1632 you intended only to read from the file, use "E<lt>". See
1635 =item Hexadecimal number > 0xffffffff non-portable
1637 (W) The hexadecimal number you specified is larger than 2**32-1
1638 (4294967295) and therefore non-portable between systems. See
1639 L<perlport> for more on portability concerns.
1641 =item Ill-formed CRTL environ value "%s"
1643 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
1644 environ array, and encountered an element without the C<=> delimiter
1645 used to spearate keys from values. The element is ignored.
1647 =item Ill-formed message in prime_env_iter: |%s|
1649 (W) A warning peculiar to VMS. Perl tried to read a logical name
1650 or CLI symbol definition when preparing to iterate over %ENV, and
1651 didn't see the expected delimiter between key and value, so the
1654 =item Illegal binary digit %s
1656 (F) You used a digit other than 0 or 1 in a binary number.
1658 =item Illegal binary digit %s ignored
1660 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
1661 Interpretation of the binary number stopped before the offending digit.
1663 =item Illegal number of bits in vec
1665 (F) The number of bits in vec() (the third argument) must be a power of
1666 two from 1 to 32 (or 64, if your platform supports that).
1668 =item Integer overflow in %s number
1670 (W) The hexadecimal, octal or binary number you have specified either
1671 as a literal or as an argument to hex() or oct() is too big for your
1672 architecture, and has been converted to a floating point number. On a
1673 32-bit architecture the largest hexadecimal, octal or binary number
1674 representable without overflow is 0xFFFFFFFF, 037777777777, or
1675 0b11111111111111111111111111111111 respectively. Note that Perl
1676 transparently promotes all numbers to a floating point representation
1677 internally--subject to loss of precision errors in subsequent
1680 =item Invalid %s attribute: %s
1682 The indicated attribute for a subroutine or variable was not recognized
1683 by Perl or by a user-supplied handler. See L<attributes>.
1685 =item Invalid %s attributes: %s
1687 The indicated attributes for a subroutine or variable were not recognized
1688 by Perl or by a user-supplied handler. See L<attributes>.
1690 =item invalid [] range "%s" in regexp
1692 The offending range is now explicitly displayed.
1694 =item Invalid separator character %s in attribute list
1696 (F) Something other than a comma or whitespace was seen between the
1697 elements of an attribute list. If the previous attribute
1698 had a parenthesised parameter list, perhaps that list was terminated
1699 too soon. See L<attributes>.
1701 =item Invalid separator character %s in subroutine attribute list
1703 (F) Something other than a comma or whitespace was seen between the
1704 elements of a subroutine attribute list. If the previous attribute
1705 had a parenthesised parameter list, perhaps that list was terminated
1708 =item leaving effective %s failed
1710 (F) While under the C<use filetest> pragma, switching the real and
1711 effective uids or gids failed.
1713 =item Lvalue subs returning %s not implemented yet
1715 (F) Due to limitations in the current implementation, array and hash
1716 values cannot be returned in subroutines used in lvalue context.
1717 See L<perlsub/"Lvalue subroutines">.
1719 =item Method %s not permitted
1723 =item Missing %sbrace%s on \N{}
1725 (F) Wrong syntax of character name literal C<\N{charname}> within
1726 double-quotish context.
1728 =item Missing command in piped open
1730 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
1731 construction, but the command was missing or blank.
1733 =item Missing name in "my sub"
1735 (F) The reserved syntax for lexically scoped subroutines requires that they
1736 have a name with which they can be found.
1738 =item no UTC offset information; assuming local time is UTC
1740 (S) A warning peculiar to VMS. Perl was unable to find the local
1741 timezone offset, so it's assuming that local system time is equivalent
1742 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
1743 to translate to the number of seconds which need to be added to UTC to
1746 =item Octal number > 037777777777 non-portable
1748 (W) The octal number you specified is larger than 2**32-1 (4294967295)
1749 and therefore non-portable between systems. See L<perlport> for more
1750 on portability concerns.
1752 See also L<perlport> for writing portable code.
1754 =item panic: del_backref
1756 (P) Failed an internal consistency check while trying to reset a weak
1759 =item panic: kid popen errno read
1761 (F) forked child returned an incomprehensible message about its errno.
1763 =item panic: magic_killbackrefs
1765 (P) Failed an internal consistency check while trying to reset all weak
1766 references to an object.
1768 =item Possible Y2K bug: %s
1770 (W) You are concatenating the number 19 with another number, which
1771 could be a potential Year 2000 problem.
1773 =item Premature end of script headers
1777 =item Repeat count in pack overflows
1779 (F) You can't specify a repeat count so large that it overflows
1780 your signed integers. See L<perlfunc/pack>.
1782 =item Repeat count in unpack overflows
1784 (F) You can't specify a repeat count so large that it overflows
1785 your signed integers. See L<perlfunc/unpack>.
1787 =item realloc() of freed memory ignored
1789 (S) An internal routine called realloc() on something that had already
1792 =item Reference is already weak
1794 (W) You have attempted to weaken a reference that is already weak.
1795 Doing so has no effect.
1797 =item setpgrp can't take arguments
1799 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
1800 unlike POSIX setpgid(), which takes a process ID and process group ID.
1802 =item Strange *+?{} on zero-length expression
1804 (W) You applied a regular expression quantifier in a place where it
1805 makes no sense, such as on a zero-width assertion.
1806 Try putting the quantifier inside the assertion instead. For example,
1807 the way to match "abc" provided that it is followed by three
1808 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
1810 =item switching effective %s is not implemented
1812 (F) While under the C<use filetest> pragma, we cannot switch the
1813 real and effective uids or gids.
1815 =item This Perl can't reset CRTL environ elements (%s)
1817 =item This Perl can't set CRTL environ elements (%s=%s)
1819 (W) Warnings peculiar to VMS. You tried to change or delete an element
1820 of the CRTL's internal environ array, but your copy of Perl wasn't
1821 built with a CRTL that contained the setenv() function. You'll need to
1822 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
1823 L<perlvms>) so that the environ array isn't the target of the change to
1824 %ENV which produced the warning.
1826 =item Unknown open() mode '%s'
1828 (F) The second argument of 3-argument open() is not among the list
1829 of valid modes: C<L<lt>>, C<L<gt>>, C<E<gt>E<gt>>, C<+L<lt>>,
1830 C<+L<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|->.
1832 =item Unknown process %x sent message to prime_env_iter: %s
1834 (P) An error peculiar to VMS. Perl was reading values for %ENV before
1835 iterating over it, and someone else stuck a message in the stream of
1836 data Perl expected. Someone's very confused, or perhaps trying to
1837 subvert Perl's population of %ENV for nefarious purposes.
1839 =item Unrecognized escape \\%c passed through
1841 (W) You used a backslash-character combination which is not recognized
1842 by Perl. The character was understood literally.
1844 =item Unterminated attribute parameter in attribute list
1846 (F) The lexer saw an opening (left) parenthesis character while parsing an
1847 attribute list, but the matching closing (right) parenthesis
1848 character was not found. You may need to add (or remove) a backslash
1849 character to get your parentheses to balance. See L<attributes>.
1851 =item Unterminated attribute list
1853 (F) The lexer found something other than a simple identifier at the start
1854 of an attribute, and it wasn't a semicolon or the start of a
1855 block. Perhaps you terminated the parameter list of the previous attribute
1856 too soon. See L<attributes>.
1858 =item Unterminated attribute parameter in subroutine attribute list
1860 (F) The lexer saw an opening (left) parenthesis character while parsing a
1861 subroutine attribute list, but the matching closing (right) parenthesis
1862 character was not found. You may need to add (or remove) a backslash
1863 character to get your parentheses to balance.
1865 =item Unterminated subroutine attribute list
1867 (F) The lexer found something other than a simple identifier at the start
1868 of a subroutine attribute, and it wasn't a semicolon or the start of a
1869 block. Perhaps you terminated the parameter list of the previous attribute
1872 =item Value of CLI symbol "%s" too long
1874 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
1875 element from a CLI symbol table, and found a resultant string longer
1876 than 1024 characters. The return value has been truncated to 1024
1879 =item Version number must be a constant number
1881 (P) The attempt to translate a C<use Module n.n LIST> statement into
1882 its equivalent C<BEGIN> block found an internal inconsistency with
1887 =head1 Obsolete Diagnostics
1891 =item Character class syntax [: :] is reserved for future extensions
1893 (W) Within regular expression character classes ([]) the syntax beginning
1894 with "[:" and ending with ":]" is reserved for future extensions.
1895 If you need to represent those character sequences inside a regular
1896 expression character class, just quote the square brackets with the
1897 backslash: "\[:" and ":\]".
1899 =item Ill-formed logical name |%s| in prime_env_iter
1901 (W) A warning peculiar to VMS. A logical name was encountered when preparing
1902 to iterate over %ENV which violates the syntactic rules governing logical
1903 names. Because it cannot be translated normally, it is skipped, and will not
1904 appear in %ENV. This may be a benign occurrence, as some software packages
1905 might directly modify logical name tables and introduce nonstandard names,
1906 or it may indicate that a logical name table has been corrupted.
1908 =item regexp too big
1910 (F) The current implementation of regular expressions uses shorts as
1911 address offsets within a string. Unfortunately this means that if
1912 the regular expression compiles to longer than 32767, it'll blow up.
1913 Usually when you want a regular expression this big, there is a better
1914 way to do it with multiple statements. See L<perlre>.
1916 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
1918 (D) Perl versions before 5.004 misinterpreted any type marker followed
1919 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
1920 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
1922 However, the developers of Perl 5.004 could not fix this bug completely,
1923 because at least two widely-used modules depend on the old meaning of
1924 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
1925 old (broken) way inside strings; but it generates this message as a
1926 warning. And in Perl 5.005, this special treatment will cease.
1932 If you find what you think is a bug, you might check the
1933 articles recently posted to the comp.lang.perl.misc newsgroup.
1934 There may also be information at http://www.perl.com/perl/, the Perl
1937 If you believe you have an unreported bug, please run the B<perlbug>
1938 program included with your release. Make sure to trim your bug down
1939 to a tiny but sufficient test case. Your bug report, along with the
1940 output of C<perl -V>, will be sent off to perlbug@perl.com to be
1941 analysed by the Perl porting team.
1945 The F<Changes> file for exhaustive details on what changed.
1947 The F<INSTALL> file for how to build Perl.
1949 The F<README> file for general stuff.
1951 The F<Artistic> and F<Copying> files for copyright information.
1955 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
1956 contributions from The Perl Porters.
1958 Send omissions or corrections to <F<perlbug@perl.com>>.