3 perldelta - what's new for perl5.006 (as of 5.005_56)
7 This document describes differences between the 5.005 release and this one.
9 =head1 Incompatible Changes
11 =head2 Perl Source Incompatibilities
13 None known at this time.
15 =head2 C Source Incompatibilities
21 Release 5.005 grandfathered old global symbol names by providing preprocessor
22 macros for extension source compatibility. As of release 5.006, these
23 preprocessor definitions are not available by default. You need to explicitly
24 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
25 extensions still using the old symbols, this option can be
26 specified via MakeMaker:
28 perl Makefile.PL POLLUTE=1
30 =item C<PERL_POLLUTE_MALLOC>
32 Enabling Perl's malloc in release 5.005 and earlier caused
33 the namespace of system versions of the malloc family of functions to
34 be usurped by the Perl versions, since by default they used the
37 Besides causing problems on platforms that do not allow these functions to
38 be cleanly replaced, this also meant that the system versions could not
39 be called in programs that used Perl's malloc. Previous versions of Perl
40 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
41 EMBEDMYMALLOC preprocessor definitions.
43 As of release 5.006, Perl's malloc family of functions have default names
44 distinct from the system versions. You need to explicitly compile perl with
45 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
46 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
49 Note that these functions do B<not> constitute Perl's memory allocation API.
50 See L<perlguts/"Memory Allocation"> for further information about that.
52 =item C<PL_na> and C<dTHR> Issues
54 The C<PL_na> global is now thread local, so a C<dTHR> declaration is needed
55 in the scope in which the global appears. XSUBs should handle this automatically,
56 but if you have used C<PL_na> in support functions, you either need to
57 change the C<PL_na> to a local variable (which is recommended), or put in
62 =head2 Compatible C Source API Changes
66 =item C<PATCHLEVEL> is now C<PERL_VERSION>
68 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
69 are now available by default from perl.h, and reflect the base revision,
70 patchlevel, and subversion respectively. C<PERL_REVISION> had no
71 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
72 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
74 The new names cause less pollution of the B<cpp> namespace and reflect what
75 the numbers have come to stand for in common practice. For compatibility,
76 the old names are still supported when F<patchlevel.h> is explicitly
77 included (as required before), so there is no source incompatibility
82 =head2 Binary Incompatibilities
84 This release is not binary compatible with the 5.005 release or its
89 =head2 Unicode and UTF-8 support
91 Perl can optionally use UTF-8 as its internal representation for character
92 strings. The C<use utf8> pragma enables this support in the current lexical
93 scope. See L<utf8> for more information.
95 =head2 Lexically scoped warning categories
97 You can now control the granularity of warnings emitted by perl at a finer
98 level using the C<use warning> pragma. See L<warning> for details.
100 =head2 Binary numbers supported
102 Binary numbers are now supported as literals, in s?printf formats, and
106 printf "The answer is: %b\n", oct("0b101010");
108 =head2 syswrite() ease-of-use
110 The length argument of C<syswrite()> is now optional.
112 =head2 64-bit support
114 Better 64-bit support -- but full support still a distant goal. One
115 must Configure with -Duse64bits to get Configure to probe for the
116 extent of 64-bit support. Depending on the platform (hints file) more
117 or less 64-awareness becomes available. As of 5.005_54 at least
118 somewhat 64-bit aware platforms are HP-UX 11 or better, Solaris 2.6 or
119 better, IRIX 6.2 or better. Naturally 64-bit platforms like Digital
120 Unix and UNICOS also have 64-bit support.
122 =head2 Better syntax checks on parenthesized unary operators
126 =head2 POSIX character class syntax [: :] supported
128 For example to match alphabetic characters use /[[:alpha:]]/.
129 See L<perlre> for details.
133 print defined(&foo,&bar,&baz);
134 print uc("foo","bar","baz");
137 used to be accidentally allowed in earlier versions, and produced
138 unpredictable behaviour. Some produced ancillary warnings
139 when used in this way; others silently did the wrong thing.
141 The parenthesized forms of most unary operators that expect a single
142 argument now ensure that they are not called with more than one
143 argument, making the cases shown above syntax errors. The usual
146 print defined &foo, &bar, &baz;
147 print uc "foo", "bar", "baz";
150 remains unchanged. See L<perlop>.
152 =head2 Improved C<qw//> operator
154 The C<qw//> operator is now evaluated at compile time into a true list
155 instead of being replaced with a run time call to C<split()>. This
156 removes the confusing misbehaviour of C<qw//> in scalar context, which
157 had inherited that behaviour from split().
161 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
163 now correctly prints "3|a", instead of "2|a".
165 =head2 pack() format 'Z' supported
167 The new format type 'Z' is useful for packing and unpacking null-terminated
168 strings. See L<perlfunc/"pack">.
170 =head2 pack() format modifier '!' supported
172 The new format type modifier '!' is useful for packing and unpacking
173 native shorts, ints, and longs. See L<perlfunc/"pack">.
175 =head2 $^X variables may now have names longer than one character
177 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
178 error. Now variable names that begin with a control character may be
179 arbitrarily long. However, for compatibility reasons, these variables
180 I<must> be written with explicit braces, as C<${^XY}> for example.
181 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
182 than one control character, such as C<${^XY^Z}>, are illegal.
184 The old syntax has not changed. As before, `^X' may be either a
185 literal control-X character or the two-character sequence `caret' plus
186 `X'. When braces are omitted, the variable name stops after the
187 control character. Thus C<"$^XYZ"> continues to be synonymous with
188 C<$^X . "YZ"> as before.
190 As before, lexical variables may not have names beginning with control
191 characters. As before, variables whose names begin with a control
192 character are always forced to be in package `main'. All such variables
193 are reserved for future extensions, except those that begin with
194 C<^_>, which may be used by user programs and is guaranteed not to
195 acquire special meaning in any future version of Perl.
197 =head1 Significant bug fixes
199 =head2 E<lt>HANDLEE<gt> on empty files
201 With C<$/> set to C<undef>, slurping an empty file returns a string of
202 zero length (instead of C<undef>, as it used to) the first time the
203 HANDLE is read. Further reads yield C<undef>.
205 This means that the following will append "foo" to an empty file (it used
208 perl -0777 -pi -e 's/^/foo/' empty_file
212 perl -pi -e 's/^/foo/' empty_file
214 is unchanged (it continues to leave the file empty).
216 =head2 C<eval '...'> improvements
218 Line numbers (as reflected by caller() and most diagnostics) within
219 C<eval '...'> were often incorrect when here documents were involved.
220 This has been corrected.
222 Lexical lookups for variables appearing in C<eval '...'> within
223 functions that were themselves called within an C<eval '...'> were
224 searching the wrong place for lexicals. The lexical search now
225 correctly ends at the subroutine's block boundary.
227 Parsing of here documents used to be flawed when they appeared as
228 the replacement expression in C<eval 's/.../.../e'>. This has
231 =head2 Automatic flushing of output buffers
233 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
234 of all files opened for output when the operation
235 was attempted. This mostly eliminates confusing
236 buffering mishaps suffered by users unaware of how Perl internally
239 =head2 Better diagnostics on meaningless filehandle operations
241 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
242 are compile time errors. Attempting to read from filehandles that
243 were opened only for writing will now produce warnings (just as
244 writing to read-only filehandles does).
246 =head1 Supported Platforms
252 VM/ESA is now supported.
256 Siemens BS2000 is now supported under the POSIX Shell.
260 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
265 GNU/Hurd is now supported.
269 Rhapsody is now supported.
273 EPOC is is now supported (on Psion 5).
283 IO constants (SEEK_*, _IO*).
287 Directory-related IO methods (new, read, close, rewind, tied delete).
289 =item op/io_multihomed
291 INET sockets with multi-homed hosts.
307 Verify operations that access pad objects (lexicals and temporaries).
311 =head1 Modules and Pragmata
319 Added Dumpvalue module provides screen dumps of Perl data.
323 You can now run tests for I<n> seconds instead of guessing the right
324 number of tests to run: e.g. timethese(-5, ...) will run each
325 code for at least 5 CPU seconds. Zero as the "number of repetitions"
326 means "for at least 3 CPU seconds". The output format has also
327 changed. For example:
329 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
331 will now output something like this:
333 Benchmark: running a, b, each for at least 5 CPU seconds...
334 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
335 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
337 New features: "each for at least N CPU seconds...", "wallclock secs",
338 and the "@ operations/CPU second (n=operations)".
342 The Devel::Peek module provides access to the internal representation
343 of Perl variables and data. It is a data debugging tool for the XS programmer.
347 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
348 large (more than 4G) file access (64-bit support is not yet
349 working, though, so no need to get overly excited), Free/Net/OpenBSD
350 locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
351 O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
355 New methods have been added to the File::Spec module: devnull() returns
356 the name of the null device (/dev/null on Unix) and tmpdir() the name of
357 the temp directory (normally /tmp on Unix). There are now also methods
358 to convert between absolute and relative filenames: abs2rel() and
359 rel2abs(). For compatibility with operating systems that specify volume
360 names in file paths, the splitpath(), splitdir(), and catdir() methods
363 =item File::Spec::Functions
365 The new File::Spec::Functions modules provides a function interface
366 to the File::Spec module. Allows shorthand
368 $fullname = catfile($dir1, $dir2, $file);
372 $fullname = File::Spec->catfile($dir1, $dir2, $file);
376 The logical operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
377 and C<~> are now supported on bigints.
381 The accessor methods Re, Im, arg, abs, rho, and theta can now also
382 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
386 A little bit of radial trigonometry (cylindrical and spherical),
387 radial coordinate conversions, and the great circle distance were added.
391 An EXISTS method has been added to this module (and sdbm_exists() has
392 been added to the underlying sdbm library), so one can now call exists
393 on an SDBM_File tied hash and get the correct result, rather than a
398 The timelocal() and timegm() functions used to silently return bogus
399 results when the date exceeded the machine's integer range. They
400 now consistently croak() if the date falls in an unsupported range.
404 The error return value in list context has been changed for all functions
405 that return a list of values. Previously these functions returned a list
406 with a single element C<undef> if an error occurred. Now these functions
407 return the empty list in these situations. This applies to the following
413 The remaining functions are unchanged and continue to return C<undef> on
414 error even in list context.
416 The Win32::SetLastError(ERROR) function has been added as a complement
417 to the Win32::GetLastError() function.
419 The new Win32::GetFullPathName(FILENAME) returns the full absolute
420 pathname for FILENAME in scalar context. In list context it returns
421 a two-element list containing the fully qualified directory name and
426 A new feature called "DBM Filters" has been added to all the
427 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
428 DBM Filters add four new methods to each DBM module:
435 These can be used to filter key-value pairs before the pairs are
436 written to the database or just after they are read from the database.
437 See L<perldbmfilter> for further information.
443 C<use utf8> to enable UTF-8 and Unicode support.
445 C<use caller 'encoding'> allows modules to inherit pragmatic attributes
446 from the caller's context. C<encoding> is currently the only supported
449 Lexical warnings pragma, C<use warning;>, to control optional warnings.
451 C<use filetest> to control the behaviour of filetests (C<-r> C<-w> ...).
452 Currently only one subpragma implemented, "use filetest 'access';",
453 that enables the use of access(2) or equivalent to check
454 permissions instead of using stat(2) as usual. This matters
455 in filesystems where there are ACLs (access control lists): the
456 stat(2) might lie, but access(2) knows better.
458 =head1 Utility Changes
462 =head1 Documentation Changes
466 =item perlopentut.pod
468 A tutorial on using open() effectively.
472 A tutorial that introduces the essentials of references.
476 A tutorial on managing class data for object modules.
480 =head1 New Diagnostics
482 =item /%s/: Unrecognized escape \\%c passed through
484 (W) You used a backslash-character combination which is not recognized
485 by Perl. This combination appears in an interpolated variable or a
486 C<'>-delimited regular expression.
488 =item Filehandle %s opened only for output
490 (W) You tried to read from a filehandle opened only for writing. If you
491 intended it to be a read-write filehandle, you needed to open it with
492 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
493 you intended only to read from the file, use "E<lt>". See
496 =item Missing command in piped open
498 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
499 construction, but the command was missing or blank.
501 =item Unrecognized escape \\%c passed through
503 (W) You used a backslash-character combination which is not recognized
506 =item defined(@array) is deprecated
508 (D) defined() is not usually useful on arrays because it checks for an
509 undefined I<scalar> value. If you want to see if the array is empty,
510 just use C<if (@array) { # not empty }> for example.
512 =item defined(%hash) is deprecated
514 (D) defined() is not usually useful on hashes because it checks for an
515 undefined I<scalar> value. If you want to see if the hash is empty,
516 just use C<if (%hash) { # not empty }> for example.
518 =head1 Obsolete Diagnostics
522 =head1 Configuration Changes
524 =head2 installusrbinperl
526 You can use "Configure -Uinstallusrbinperl" which causes installperl
527 to skip installing perl also as /usr/bin/perl. This is useful if you
528 prefer not to modify /usr/bin for some reason or another but harmful
529 because many scripts assume to find Perl in /usr/bin/perl.
533 You can use "Configure -Dusesocks" which causes Perl to probe
534 for the SOCKS proxy protocol library, http://www.socks.nec.com/
538 If you find what you think is a bug, you might check the headers of
539 articles recently posted to the comp.lang.perl.misc newsgroup.
540 There may also be information at http://www.perl.com/perl/, the Perl
543 If you believe you have an unreported bug, please run the B<perlbug>
544 program included with your release. Make sure to trim your bug down
545 to a tiny but sufficient test case. Your bug report, along with the
546 output of C<perl -V>, will be sent off to perlbug@perl.com to be
547 analysed by the Perl porting team.
551 The F<Changes> file for exhaustive details on what changed.
553 The F<INSTALL> file for how to build Perl.
555 The F<README> file for general stuff.
557 The F<Artistic> and F<Copying> files for copyright information.
561 Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions
562 from The Perl Porters.
564 Send omissions or corrections to <F<perlbug@perl.com>>.