3 perldelta - what's new for perl5.005
7 This document describes differences between the 5.004 release and this one.
9 =head1 About the new versioning system
11 Perl is now developed on two tracks: a maintenance track that makes
12 small, safe updates to released production versions with emphasis on
13 compatibility; and a development track that pursues more aggressive
14 evolution. Maintenance releases (which should be considered production
15 quality) have subversion numbers that run from C<1> to C<49>, and
16 development releases (which should be considered "alpha" quality) run
19 Perl 5.005 is the combined product of the new dual-track development
22 =head1 Incompatible Changes
24 =head2 WARNING: This version is not binary compatible with Perl 5.004.
26 Starting with Perl 5.004_50 there were many deep and far-reaching changes
27 to the language internals. If you have dynamically loaded extensions
28 that you built under perl 5.003 or 5.004, you can continue to use them
29 with 5.004, but you will need to rebuild and reinstall those extensions
30 to use them 5.005. See L<INSTALL> for detailed instructions on how to
33 =head2 Default installation structure has changed
35 The new Configure defaults are designed to allow a smooth upgrade from
36 5.004 to 5.005, but you should read L<INSTALL> for a detailed
37 discussion of the changes in order to adapt them to your system.
39 =head2 Perl Source Compatibility
41 When none of the experimental features are enabled, there should be
42 very few user-visible Perl source compatibility issues.
44 If threads are enabled, then some caveats apply. C<@_> and C<$_> become
45 lexical variables. The effect of this should be largely transparent to
46 the user, but there are some boundary conditions under which user will
47 need to be aware of the issues. For example, C<local(@_)> results in
48 a "Can't localize lexical variable @_ ..." message. This may be enabled
51 Some new keywords have been introduced. These are generally expected to
52 have very little impact on compatibility. See L<New C<INIT> keyword>,
53 L<New C<lock> keyword>, and L<New C<qr//> operator>.
55 Certain barewords are now reserved. Use of these will provoke a warning
56 if you have asked for them with the C<-w> switch.
57 See L<C<our> is now a reserved word>.
59 =head2 C Source Compatibility
61 There have been a large number of changes in the internals to support
62 the new features in this release.
66 =item Core sources now require ANSI C compiler
68 An ANSI C compiler is now B<required> to build perl. See F<INSTALL>.
70 =item All Perl global variables must now be referenced with an explicit prefix
72 All Perl global variables that are visible for use by extensions now
73 have a C<PL_> prefix. New extensions should C<not> refer to perl globals
74 by their unqualified names. To preserve sanity, we provide limited
75 backward compatibility for globals that are being widely used like
76 C<sv_undef> and C<na> (which should now be written as C<PL_sv_undef>,
79 If you find that your XS extension does not compile anymore because a
80 perl global is not visible, try adding a C<PL_> prefix to the global
83 It is strongly recommended that all functions in the Perl API that don't
84 begin with C<perl> be referenced with a C<Perl_> prefix. The bare function
85 names without the C<Perl_> prefix are supported with macros, but this
86 support may cease in a future release.
88 See L<perlguts/API LISTING>.
90 =item Enabling threads has source compatibility issues
92 Perl built with threading enabled requires extensions to use the new
93 C<dTHR> macro to initialize the handle to access per-thread data.
94 If you see a compiler error that talks about the variable C<thr> not
95 being declared (when building a module that has XS code), you need
96 to add C<dTHR;> at the beginning of the block that elicited the error.
98 The API function C<perl_get_sv("@",FALSE)> should be used instead of
99 directly accessing perl globals as C<GvSV(errgv)>. The API call is
100 backward compatible with existing perls and provides source compatibility
101 with threading is enabled.
103 See L<API Changes for more information>.
107 =head2 Binary Compatibility
109 This version is NOT binary compatible with older versions. All extensions
110 will need to be recompiled. Further binaries built with threads enabled
111 are incompatible with binaries built without. This should largely be
112 transparent to the user, as all binary incompatible configurations have
113 their own unique architecture name, and extension binaries get installed at
114 unique locations. This allows coexistence of several configurations in
115 the same directory hierarchy. See F<INSTALL>.
117 =head2 Security fixes may affect compatibility
119 A few taint leaks and taint omissions have been corrected. This may lead
120 to "failure" of scripts that used to work with older versions. Compiling
121 with -DINCOMPLETE_TAINTS provides a perl with minimal amounts of changes
122 to the tainting behavior. But note that the resulting perl will have
125 Oneliners with the C<-e> switch do not create temporary files anymore.
127 =head2 Relaxed new mandatory warnings introduced in 5.004
129 Many new warnings that were introduced in 5.004 have been made
130 optional. Some of these warnings are still present, but perl's new
131 features make them less often a problem. See L<New Diagnostics>.
135 Perl has a new Social Contract for contributors. See F<Porting/Contract>.
137 The license included in much of the Perl documentation has changed.
138 Most of the Perl documentation was previously under the implicit GNU
139 General Public License or the Artistic License (at the user's choice).
140 Now much of the documentation unambigously states the terms under which
141 it may be distributed. Those terms are in general much less restrictive
142 than the GNU GPL. See L<perl> and the individual perl man pages listed
150 WARNING: Threading is considered an B<experimental> feature. Details of the
151 implementation may change without notice. There are known limitations
152 and some bugs. These are expected to be fixed in future versions.
154 See L<README.threads>.
158 WARNING: The Compiler and related tools are considered B<experimental>.
159 Features may change without notice, and there are known limitations
160 and bugs. Since the compiler is fully external to perl, the default
161 configuration will build and install it.
163 The Compiler produces three different types of transformations of a
164 perl program. The C backend generates C code that captures perl's state
165 just before execution begins. It eliminates the compile-time overheads
166 of the regular perl interpreter, but the run-time performance remains
167 comparatively the same. The CC backend generates optimized C code
168 equivivalent to the code path at run-time. The CC backend has greater
169 potential for big optimizations, but only a few optimizations are
170 implemented currently. The Bytecode backend generates a platform
171 independent bytecode representation of the interpreter's state
172 just before execution. Thus, the Bytecode back end also eliminates
173 much of the compilation overhead of the interpreter.
175 The compiler comes with several valuable utilities.
177 C<B::Lint> is an experimental module to detect and warn about suspicious
178 code, especially the cases that the C<-w> switch does not detect.
180 C<B::Deparse> can be used to demystify perl code, and understand
181 how perl optimizes certain constructs.
183 C<B::Xref> generates cross reference reports of all definition and use
184 of variables, subroutines and formats in a program.
186 C<B::Showlex> show the lexical variables used by a subroutine or file
189 C<perlcc> is a simple frontend for compiling perl.
191 See C<ext/B/README>, L<B>, and the respective compiler modules.
193 =head2 Regular Expressions
195 Perl's regular expression engine has been seriously overhauled, and
196 many new constructs are supported. Several bugs have been fixed.
198 Here is an itemized summary:
202 =item Many new and improved optimizations
204 Changes in the RE engine:
206 Unneeded nodes removed;
207 Substrings merged together;
208 New types of nodes to process (SUBEXPR)* and similar expressions
209 quickly, used if the SUBEXPR has no side effects and matches
210 strings of the same length;
211 better optimizations by lookup for constant substrings;
212 Better search for constants substrings anchored by $ ;
214 Changes in Perl code using RE engine:
216 more optimizations to s/longer/short/;
217 study() was not working;
218 /blah/ may be optimized to an analogue of index() if $& $` $' not seen;
219 Unneeded copying of matched-against string removed;
220 Only matched part of the string is copying if $` $' were not seen;
224 Note that only the major bug fixes are listed here. See F<Changes> for others.
226 Backtracking might not restore start of $3.
227 No feedback if max count for * or + on "complex" subexpression
228 was reached, similarly (but at compile time) for {3,34567}
229 Primitive restrictions on max count introduced to decrease a
230 possibility of a segfault;
231 (ZERO-LENGTH)* could segfault;
232 (ZERO-LENGTH)* was prohibited;
233 Long RE were not allowed;
234 /RE/g could skip matches at the same position after a
237 =item New regular expression constructs
239 The following new syntax elements are supported:
246 (?(COND)YES_RE|NO_RE)
250 =item New operator for precompiled regular expressions
252 See L<New C<qr//> operator>.
254 =item Other improvements
256 better debugging output (possibly with colors), even from non-debugging Perl;
257 RE engine code now looks like C, not like assembler;
258 behaviour of RE modifiable by `use re' directive;
259 Improved documentation;
260 Test suite significantly extended;
261 Syntax [:^upper:] etc., reserved inside character classes;
263 =item Incompatible changes
265 (?i) localized inside enclosing group;
266 $( is not interpolated into RE any more;
267 /RE/g may match at the same position (with non-zero length)
268 after a zero-length match (bug fix).
272 See L<perlre> and L<perlop>.
274 =head2 Improved malloc()
276 See banner at the beginning of C<malloc.c> for details.
278 =head2 Quicksort is internally implemented
280 Perl now contains its own highly optimized qsort() routine. The new qsort()
281 is resistant to inconsistent comparison functions, so Perl's C<sort()> will
282 not provoke coredumps any more when given poorly written sort subroutines.
283 (Some C library C<qsort()>s that were being used before used to have this
284 problem.) In our testing, the new C<qsort()> required the minimal number
285 of pair-wise compares on average, among all known C<qsort()> implementations.
287 See C<perlfunc/sort>.
289 =head2 Reliable signals
291 Perl's signal handling is susceptible to random crashes, because signals
292 arrive asynchronously, and the Perl runtime is not reentrant at arbitrary
295 However, one experimental implementation of reliable signals is available
296 when threads are enabled. See C<Thread::Signal>. Also see F<INSTALL> for
297 how to build a Perl capable of threads.
299 =head2 Reliable stack pointers
301 The internals now reallocate the perl stack only at predictable times.
302 In particular, magic calls never trigger reallocations of the stack,
303 because all reentrancy of the runtime is handled using a "stack of stacks".
304 This should improve reliability of cached stack pointers in the internals
307 =head2 More generous treatment of carriage returns
309 Perl used to complain if it encountered literal carriage returns in
310 scripts. Now they are mostly treated like whitespace within program text.
311 Inside string literals and here documents, literal carriage returns are
312 ignored if they occur paired with newlines, or get interpreted as newlines
313 if they stand alone. This behavior means that literal carriage returns
314 in files should be avoided. You can get the older, more compatible (but
315 less generous) behavior by defining the preprocessor symbol
316 C<PERL_STRICT_CR> when building perl. Of course, all this has nothing
317 whatever to do with how escapes like C<\r> are handled within strings.
319 Note that this doesn't somehow magically allow you to keep all text files
320 in DOS format. The generous treatment only applies to files that perl
321 itself parses. If your C compiler doesn't allow carriage returns in
322 files, you may still be unable to build modules that need a C compiler.
326 C<substr>, C<pos> and C<vec> don't leak memory anymore when used in lvalue
327 context. Many small leaks that impacted applications that embed multiple
328 interpreters have been fixed.
330 =head2 Better support for multiple interpreters
332 The build-time option C<-DMULTIPLICITY> has had many of the details
333 reworked. Some previously global variables that should have been
334 per-interpreter now are. With care, this allows interpreters to call
335 each other. See the C<PerlInterp> extension on CPAN.
337 =head2 Behavior of local() on array and hash elements is now well-defined
339 See L<perlsub/"Temporary Values via local()">.
341 =head2 C<%!> is transparently tied to the L<Errno> module
343 See L<perlvar>, and L<Errno>.
345 =head2 Pseudo-hashes are supported
349 =head2 C<EXPR foreach EXPR> is supported
353 =head2 Keywords can be globally overridden
357 =head2 C<$^E> is meaningful on Win32
361 =head2 C<foreach (1..1000000)> optimized
363 C<foreach (1..1000000)> is now optimized into a counting loop. It does
364 not try to allocate a 1000000-size list anymore.
366 =head2 C<Foo::> can be used as implicitly quoted package name
368 Barewords caused unintuitive behavior when a subroutine with the same
369 name as a package happened to be defined. Thus, C<new Foo @args>,
370 use the result of the call to C<Foo()> instead of C<Foo> being treated
371 as a literal. The recommended way to write barewords in the indirect
372 object slot is C<new Foo:: @args>. Note that the method C<new()> is
373 called with a first argument of C<Foo>, not C<Foo::> when you do that.
375 =head2 C<exists $Foo::{Bar::}> tests existence of a package
377 It was impossible to test for the existence of a package without
378 actually creating it before. Now C<exists $Foo::{Bar::}> can be
379 used to test if the C<Foo::Bar> namespace has been created.
381 =head2 Better locale support
385 =head2 Experimental support for 64-bit platforms
387 Perl5 has always had 64-bit support on systems with 64-bit longs.
388 Starting with 5.005, the beginnings of experimental support for systems
389 with 32-bit long and 64-bit 'long long' integers has been added.
390 If you add -DUSE_LONG_LONG to your ccflags in config.sh (or manually
391 define it in perl.h) then perl will be built with 'long long' support.
392 There will be many compiler warnings, and the resultant perl may not
393 work on all systems. There are many other issues related to
394 third-party extensions and libraries. This option exists to allow
395 people to work on those issues.
397 =head2 prototype() returns useful results on builtins
399 See L<perlfunc/prototype>.
401 =head2 Extended support for exception handling
403 C<die()> now accepts a reference value, and C<$@> gets set to that
404 value in exception traps. This makes it possible to propagate
405 exception objects. This is an undocumented B<experimental> feature.
407 =head2 Re-blessing in DESTROY() supported for chaining DESTROY() methods
409 See L<perlobj/Destructors>.
411 =head2 All C<printf> format conversions are handled internally
413 See L<perlfunc/printf>.
415 =head2 New C<INIT> keyword
417 C<INIT> subs are like C<BEGIN> and C<END>, but they get run just before
418 the perl runtime begins execution. e.g., the Perl Compiler makes use of
419 C<INIT> blocks to initialize and resolve pointers to XSUBs.
421 =head2 New C<lock> keyword
423 The C<lock> keyword is the fundamental synchronization primitive
424 in threaded perl. When threads are not enabled, it is currently a noop.
426 To minimize impact on source compatibility this keyword is "weak", i.e., any
427 user-defined subroutine of the same name overrides it, unless a C<use Thread>
430 =head2 New C<qr//> operator
432 The C<qr//> operator, which is syntactically similar to the other quote-like
433 operators, is used to create precompiled regular expressions. This compiled
434 form can now be explicitly passed around in variables, and interpolated in
435 other regular expressions. See L<perlop>.
437 =head2 C<our> is now a reserved word
439 Calling a subroutine with the name C<our> will now provoke a warning when
440 using the C<-w> switch.
442 =head2 Tied arrays are now fully supported
446 =head2 Tied handles support is better
448 Several missing hooks have been added. There is also a new base class for
449 TIEARRAY implementations. See L<Tie::Array>.
451 =head2 4th argument to substr
453 substr() can now both return and replace in one operation. The optional
454 4th argument is the replacement string. See L<perlfunc/substr>.
456 =head2 Negative LENGTH argument to splice
458 Splice() with a negative LENGTH argument now work similar to what the
459 LENGTH did for substr(). Previously a negative LENGTH was treated as
460 0. See L<perlfunc/splice>.
462 =head2 Magic lvalues are now more magical
464 When you say something like C<substr($x, 5) = "hi">, the scalar returned
465 by substr() is special, in that any modifications to it affect $x.
466 (This is called a 'magic lvalue' because an 'lvalue' is something on
467 the left side of an assignment.) Normally, this is exactly what you
468 would expect to happen, but Perl uses the same magic if you use substr(),
469 pos(), or vec() in a context where they might be modified, like taking
470 a reference with C<\> or as an argument to a sub that modifies C<@_>.
471 In previous versions, this 'magic' only went one way, but now changes
472 to the scalar the magic refers to ($x in the above example) affect the
473 magic lvalue too. For instance, this code now acts differently:
480 printit(substr($x, 0, 5));
482 In previous versions, this would print "hello", but it now prints "g'bye".
484 =head2 E<lt>E<gt> now reads in records
486 If C<$/> is a referenence to an integer, or a scalar that holds an integer,
487 E<lt>E<gt> will read in records instead of lines. For more info, see
490 =head1 Supported Platforms
492 Configure has many incremental improvements. Site-wide policy for building
493 perl can now be made persistent, via Policy.sh. Configure also records
494 the command-line arguments used in F<config.sh>.
498 BeOS is now supported. See L<README.beos>.
500 DOS is now supported under the DJGPP tools. See L<README.dos>.
502 MPE/iX is now supported. See L<README.mpeix>.
504 =head2 Changes in existing support
506 Win32 support has been vastly enhanced. Support for Perl Object, a C++
507 encapsulation of Perl. GCC and EGCS are now supported on Win32.
508 See F<README.win32>, aka L<perlwin32>.
510 VMS configuration system has been rewritten. See L<README.vms>.
512 The hints files for most Unix platforms have seen incremental improvements.
514 =head1 Modules and Pragmata
522 Perl compiler and tools. See L<B>.
526 A module to pretty print Perl data. See L<Data::Dumper>.
530 A module to look up errors more conveniently. See L<Errno>.
534 A portable API for file operations.
536 =item ExtUtils::Installed
538 Query and manage installed modules.
540 =item ExtUtils::Packlist
542 Manipulate .packlist files.
546 Make functions/builtins succeed or die.
550 Constants and other support infrastructure for System V IPC operations
555 A framework for writing testsuites.
559 Base class for tied arrays.
563 Base class for tied handles.
567 Perl thread creation, manipulation, and support.
571 Set subroutine attributes.
575 Compile-time class fields.
579 Various pragmata to control behavior of regular expressions.
583 =head2 Changes in existing modules
589 CGI has been updated to version 2.42.
593 POSIX now has its own platform-specific hints files.
597 DB_File supports version 2.x of Berkeley DB. See C<ext/DB_File/Changes>.
601 MakeMaker now supports writing empty makefiles, provides a way to
602 specify that site umask() policy should be honored. There is also
603 better support for manipulation of .packlist files, and getting
604 information about installed modules.
606 Extensions that have both architecture-dependent and
607 architecture-independent files are now always installed completely in
608 the architecture-dependent locations. Previously, the shareable parts
609 were shared both across architectures and across perl versions and were
610 therefore liable to be overwritten with newer versions that might have
611 subtle incompatibilities.
615 See <perlmodinstall> and L<CPAN>.
619 Cwd::cwd is faster on most platforms.
627 =head1 Utility Changes
629 C<h2ph> and related utilities have been vastly overhauled.
631 C<perlcc>, a new experimental front end for the compiler is available.
633 The crude GNU C<configure> emulator is now called C<configure.gnu> to
634 avoid trampling on C<Configure> under case-insensitive filesystems.
636 C<perldoc> used to be rather slow. The slower features are now optional.
637 In particular, case-insensitive searches need the C<-i> switch, and
638 recursive searches need C<-r>. You can set these switches in the
639 C<PERLDOC> environment variable to get the old behavior.
641 =head1 Documentation Changes
643 Config.pm now has a glossary of variables.
645 F<Porting/patching.pod> has detailed instructions on how to create and
646 submit patches for perl.
648 L<perlport> specifies guidelines on how to write portably.
650 L<perlmodinstall> describes how to fetch and install modules from C<CPAN>
653 Some more Perl traps are documented now. See L<perltrap>.
655 =head1 New Diagnostics
659 =item Ambiguous call resolved as CORE::%s(), qualify as such or use &
661 (W) A subroutine you have declared has the same name as a Perl keyword,
662 and you have used the name without qualification for calling one or the
663 other. Perl decided to call the builtin because the subroutine is
666 To force interpretation as a subroutine call, either put an ampersand
667 before the subroutine name, or qualify the name with its package.
668 Alternatively, you can import the subroutine (or pretend that it's
669 imported with the C<use subs> pragma).
671 To silently interpret it as the Perl operator, use the C<CORE::> prefix
672 on the operator (e.g. C<CORE::log($x)>) or by declaring the subroutine
673 to be an object method (see L<attrs>).
675 =item Bad index while coercing array into hash
677 (F) The index looked up in the hash found as the 0'th element of a
678 pseudo-hash is not legal. Index values must be at 1 or greater.
681 =item Bareword "%s" refers to nonexistent package
683 (W) You used a qualified bareword of the form C<Foo::>, but
684 the compiler saw no other uses of that namespace before that point.
685 Perhaps you need to predeclare a package?
687 =item Can't call method "%s" on an undefined value
689 (F) You used the syntax of a method call, but the slot filled by the
690 object reference or package name contains an undefined value.
691 Something like this will reproduce the error:
694 process $BADREF 1,2,3;
695 $BADREF->process(1,2,3);
697 =item Can't coerce array into hash
699 (F) You used an array where a hash was expected, but the array has no
700 information on how to map from keys to array indices. You can do that
701 only with arrays that have a hash reference at index 0.
703 =item Can't goto subroutine from an eval-string
705 (F) The "goto subroutine" call can't be used to jump out of an eval "string".
706 (You can use it to jump out of an eval {BLOCK}, but you probably don't want to.)
708 =item Can't localize pseudo-hash element
710 (F) You said something like C<local $ar-E<gt>{'key'}>, where $ar is
711 a reference to a pseudo-hash. That hasn't been implemented yet, but
712 you can get a similar effect by localizing the corresponding array
713 element directly -- C<local $ar-E<gt>[$ar-E<gt>[0]{'key'}]>.
715 =item Can't use %%! because Errno.pm is not available
717 (F) The first time the %! hash is used, perl automatically loads the
718 Errno.pm module. The Errno module is expected to tie the %! hash to
719 provide symbolic names for C<$!> errno values.
721 =item Cannot find an opnumber for "%s"
723 (F) A string of a form C<CORE::word> was given to prototype(), but
724 there is no builtin with the name C<word>.
726 =item Character class syntax [. .] is reserved for future extensions
728 (W) Within regular expression character classes ([]) the syntax beginning
729 with "[." and ending with ".]" is reserved for future extensions.
730 If you need to represent those character sequences inside a regular
731 expression character class, just quote the square brackets with the
732 backslash: "\[." and ".\]".
734 =item Character class syntax [: :] is reserved for future extensions
736 (W) Within regular expression character classes ([]) the syntax beginning
737 with "[:" and ending with ":]" is reserved for future extensions.
738 If you need to represent those character sequences inside a regular
739 expression character class, just quote the square brackets with the
740 backslash: "\[:" and ":\]".
742 =item Character class syntax [= =] is reserved for future extensions
744 (W) Within regular expression character classes ([]) the syntax
745 beginning with "[=" and ending with "=]" is reserved for future extensions.
746 If you need to represent those character sequences inside a regular
747 expression character class, just quote the square brackets with the
748 backslash: "\[=" and "=\]".
750 =item %s: Eval-group in insecure regular expression
752 (F) Perl detected tainted data when trying to compile a regular expression
753 that contains the C<(?{ ... })> zero-width assertion, which is unsafe.
754 See L<perlre/(?{ code })>, and L<perlsec>.
756 =item %s: Eval-group not allowed, use re 'eval'
758 (F) A regular expression contained the C<(?{ ... })> zero-width assertion,
759 but that construct is only allowed when the C<use re 'eval'> pragma is
760 in effect. See L<perlre/(?{ code })>.
762 =item %s: Eval-group not allowed at run time
764 (F) Perl tried to compile a regular expression containing the C<(?{ ... })>
765 zero-width assertion at run time, as it would when the pattern contains
766 interpolated values. Since that is a security risk, it is not allowed.
767 If you insist, you may still do this by explicitly building the pattern
768 from an interpolated string at run time and using that in an eval().
769 See L<perlre/(?{ code })>.
771 =item Explicit blessing to '' (assuming package main)
773 (W) You are blessing a reference to a zero length string. This has
774 the effect of blessing the reference into the package main. This is
775 usually not what you want. Consider providing a default target
776 package, e.g. bless($ref, $p or 'MyPackage');
778 =item Illegal hex digit ignored
780 (W) You may have tried to use a character other than 0 - 9 or A - F in a
781 hexadecimal number. Interpretation of the hexadecimal number stopped
782 before the illegal character.
784 =item No such array field
786 (F) You tried to access an array as a hash, but the field name used is
787 not defined. The hash at index 0 should map all valid field names to
788 array indices for that to work.
790 =item No such field "%s" in variable %s of type %s
792 (F) You tried to access a field of a typed variable where the type
793 does not know about the field name. The field names are looked up in
794 the %FIELDS hash in the type package at compile time. The %FIELDS hash
795 is usually set up with the 'fields' pragma.
797 =item Out of memory during ridiculously large request
799 (F) You can't allocate more than 2^31+"small amount" bytes. This error
800 is most likely to be caused by a typo in the Perl program. e.g., C<$arr[time]>
801 instead of C<$arr[$time]>.
803 =item Range iterator outside integer range
805 (F) One (or both) of the numeric arguments to the range operator ".."
806 are outside the range which can be represented by integers internally.
807 One possible workaround is to force Perl to use magical string
808 increment by prepending "0" to your numbers.
810 =item Recursive inheritance detected while looking for method '%s' in package '%s'
812 (F) More than 100 levels of inheritance were encountered while invoking a
813 method. Probably indicates an unintended loop in your inheritance hierarchy.
815 =item Reference found where even-sized list expected
817 (W) You gave a single reference where Perl was expecting a list with
818 an even number of elements (for assignment to a hash). This
819 usually means that you used the anon hash constructor when you meant
820 to use parens. In any case, a hash requires key/value B<pairs>.
822 %hash = { one => 1, two => 2, }; # WRONG
823 %hash = [ qw/ an anon array / ]; # WRONG
824 %hash = ( one => 1, two => 2, ); # right
825 %hash = qw( one 1 two 2 ); # also fine
827 =item Undefined value assigned to typeglob
829 (W) An undefined value was assigned to a typeglob, a la C<*foo = undef>.
830 This does nothing. It's possible that you really mean C<undef *foo>.
832 =item Use of reserved word "%s" is deprecated
834 (D) The indicated bareword is a reserved word. Future versions of perl
835 may use it as a keyword, so you're better off either explicitly quoting
836 the word in a manner appropriate for its context of use, or using a
837 different name altogether. The warning can be suppressed for subroutine
838 names by either adding a C<&> prefix, or using a package qualifier,
839 e.g. C<&our()>, or C<Foo::our()>.
841 =item perl: warning: Setting locale failed.
843 (S) The whole warning message will look something like:
845 perl: warning: Setting locale failed.
846 perl: warning: Please check that your locale settings:
849 are supported and installed on your system.
850 perl: warning: Falling back to the standard locale ("C").
852 Exactly what were the failed locale settings varies. In the above the
853 settings were that the LC_ALL was "En_US" and the LANG had no value.
854 This error means that Perl detected that you and/or your system
855 administrator have set up the so-called variable system but Perl could
856 not use those settings. This was not dead serious, fortunately: there
857 is a "default locale" called "C" that Perl can and will use, the
858 script will be run. Before you really fix the problem, however, you
859 will get the same error message each time you run Perl. How to really
860 fix the problem can be found in L<perllocale> section B<LOCALE PROBLEMS>.
865 =head1 Obsolete Diagnostics
871 (F) The mktemp() routine failed for some reason while trying to process
872 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
874 =item Can't write to temp file for B<-e>: %s
876 (F) The write routine failed for some reason while trying to process
877 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
879 =item Cannot open temporary file
881 (F) The create routine failed for some reason while trying to process
882 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
888 If you find what you think is a bug, you might check the headers of
889 recently posted articles in the comp.lang.perl.misc newsgroup.
890 There may also be information at http://www.perl.com/perl/, the Perl
893 If you believe you have an unreported bug, please run the B<perlbug>
894 program included with your release. Make sure you trim your bug down
895 to a tiny but sufficient test case. Your bug report, along with the
896 output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be
897 analysed by the Perl porting team.
901 The F<Changes> file for exhaustive details on what changed.
903 The F<INSTALL> file for how to build Perl.
905 The F<README> file for general stuff.
907 The F<Artistic> and F<Copying> files for copyright information.
911 Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions
912 from The Perl Porters.
914 Send omissions or corrections to <F<perlbug@perl.com>>.