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1=head1 NAME
2
a5222a85 3perldelta - what's new for perl v5.6 (as of v5.005_62)
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4
5=head1 DESCRIPTION
6
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7This is an unsupported alpha release, meant for intrepid Perl developers
8only. The included sources may not even build correctly on some platforms.
9Subscribing to perl5-porters is the best way to monitor and contribute
10to the progress of development releases (see www.perl.org for info).
11
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12This document describes differences between the 5.005 release and this one.
13
14=head1 Incompatible Changes
15
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16=head2 Perl Source Incompatibilities
17
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18Beware that any new warnings that have been added or enhanced old
19warnings are B<not> considered incompatible changes.
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20
21Since all new warnings must be explicitly requested via the C<-w>
22switch or the C<warnings> pragma, it is ultimately the programmer's
23responsibility to ensure that warnings are enabled judiciously.
e02fdbd2 24
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25=over 4
26
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27=item Treatment of list slices of undef has changed
28
29When taking a slice of a literal list (as opposed to a slice of
30an array or hash), Perl used to return an empty list if the
31result happened to be composed of all undef values.
32
33The new behavior is to produce an empty list if (and only if)
34the original list was empty. Consider the following example:
35
36 @a = (1,undef,undef,2)[2,1,2];
37
38The old behavior would have resulted in @a having no elements.
39The new behavior ensures it has three undefined elements.
40
41Note in particular that the behavior of slices of the following
42cases remains unchanged:
43
44 @a = ()[1,2];
45 @a = (getpwent)[7,0];
46 @a = (anything_returning_empty_list())[2,1,2];
47 @a = @b[2,1,2];
48 @a = @c{'a','b','c'};
49
50See L<perldata>.
51
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52=item Possibly changed pseudo-random number generator
53
54In 5.005_0x and earlier, perl's rand() function used the C library
55rand(3) function. As of 5.005_52, Configure tests for drand48(),
56random(), and rand() (in that order) and picks the first one it finds.
57Perl programs that depend on reproducing a specific set of pseudo-random
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58numbers will now likely produce different output. You can use
59C<sh Configure -Drandfunc=rand> to obtain the old behavior.
757edf6f 60
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61=item Hashing function for hash keys has changed
62
63Perl hashes are not order preserving. The apparently random order
64encountered when iterating on the contents of a hash is determined
65by the hashing algorithm used. To improve the distribution of lower
66bits in the hashed value, the algorithm has changed slightly as of
675.005_52. When iterating over hashes, this may yield a random order
68that is B<different> from that of previous versions.
69
70=item C<undef> fails on read only values
71
72Using the C<undef> operator on a readonly value (such as $1) has
73the same effect as assigning C<undef> to the readonly value--it
74throws an exception.
75
76=item Close-on-exec bit may be set on pipe() handles
77
78On systems that support a close-on-exec flag on filehandles, the
79flag will be set for any handles created by pipe(), if that is
80warranted by the value of $^F that may be in effect. Earlier
81versions neglected to set the flag for handles created with
82pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
83
84=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
85
86Perl 5.004 deprecated the interpretation of C<$$1> and
87similar within interpolated strings to mean C<$$ . "1">,
88but still allowed it.
89
90In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
91
92=item values(%h) and C<\(%h)> operate on aliases to values, not copies
93
94each(), values() and hashes in a list context return the actual
95values in the hash, instead of copies (as they used to in earlier
96versions). Typical idioms for using these constructs copy the
501fbaef 97returned values, but this can make a significant difference when
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98creating references to the returned values.
99
100Keys in the hash are still returned as copies when iterating on
08cd8952 101a hash.
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102
103=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
104
08cd8952 105vec() generates a run-time error if the BITS argument is not
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106a valid power-of-two integer.
107
108=item Text of some diagnostic output has changed
109
110Most references to internal Perl operations in diagnostics
111have been changed to be more descriptive. This may be an
112issue for programs that may incorrectly rely on the exact
113text of diagnostics for proper functioning.
114
115=item C<%@> has been removed
116
117The undocumented special variable C<%@> that used to accumulate
118"background" errors (such as those that happen in DESTROY())
119has been removed, because it could potentially result in memory
120leaks.
121
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122=back
123
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124=head2 C Source Incompatibilities
125
126=over 4
127
128=item C<PERL_POLLUTE>
129
130Release 5.005 grandfathered old global symbol names by providing preprocessor
87275199 131macros for extension source compatibility. As of release 5.6, these
e02fdbd2 132preprocessor definitions are not available by default. You need to explicitly
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133compile perl with C<-DPERL_POLLUTE> to get these definitions. For
134extensions still using the old symbols, this option can be
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135specified via MakeMaker:
136
14218588 137 perl Makefile.PL POLLUTE=1
e02fdbd2 138
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139=item C<PERL_IMPLICIT_CONTEXT>
140
141This new build option provides a set of macros for all API functions
142such that an implicit interpreter/thread context argument is passed to
143every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 144amounts to a macro invocation that actually translates to something like
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145C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
146to not have any significant source compatibility issues, the difference
147between a macro and a real function call will need to be considered.
148
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149This means that there B<is> a source compatibility issue as a result of
150this if your extensions attempt to use pointers to any of the Perl API
151functions.
152
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153Note that the above issue is not relevant to the default build of
154Perl, whose interfaces continue to match those of prior versions
155(but subject to the other options described here).
156
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157PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
158with one of -Dusethreads, -Dusemultiplicity, or both.
f29c64d6 159
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160See L<perlguts/"The Perl API"> for detailed information on the
161ramifications of building Perl using this option.
162
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163=item C<PERL_POLLUTE_MALLOC>
164
14218588 165Enabling Perl's malloc in release 5.005 and earlier caused
86058a2d 166the namespace of system versions of the malloc family of functions to
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167be usurped by the Perl versions, since by default they used the
168same names.
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169
170Besides causing problems on platforms that do not allow these functions to
171be cleanly replaced, this also meant that the system versions could not
172be called in programs that used Perl's malloc. Previous versions of Perl
14218588 173have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
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174EMBEDMYMALLOC preprocessor definitions.
175
87275199 176As of release 5.6, Perl's malloc family of functions have default names
86058a2d 177distinct from the system versions. You need to explicitly compile perl with
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178C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
179and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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180the default.
181
182Note that these functions do B<not> constitute Perl's memory allocation API.
183See L<perlguts/"Memory Allocation"> for further information about that.
184
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185=back
186
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187=head2 Compatible C Source API Changes
188
189=over
190
191=item C<PATCHLEVEL> is now C<PERL_VERSION>
192
14218588 193The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 194are now available by default from perl.h, and reflect the base revision,
14218588 195patchlevel, and subversion respectively. C<PERL_REVISION> had no
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196prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
197previously available as C<PATCHLEVEL> and C<SUBVERSION>.
198
14218588 199The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 200the numbers have come to stand for in common practice. For compatibility,
14218588 201the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 202included (as required before), so there is no source incompatibility
14218588 203from the change.
cceca5ed 204
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205=item Support for C++ exceptions
206
207change#3386, also needs perlguts documentation
208[TODO - Chip Salzenberg <chip@perlsupport.com>]
209
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210=back
211
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212=head2 Binary Incompatibilities
213
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214The default build of this release is binary compatible with the 5.005
215release or its maintenance versions.
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216
217The usethreads or usemultiplicity builds are B<not> binary compatible
218with the corresponding builds in 5.005.
e02fdbd2 219
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220=head1 Installation and Configuration Improvements
221
222=head2 New Configure flags
223
224The following new flags may be enabled on the Configure command line
225by running Configure with C<-Dflag>.
226
227 usemultiplicity
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228
229 uselongdouble
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230 usemorebits
231 uselargefiles
a5222a85 232
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233=head2 -Dusethreads and -Duse64bits now more daring
234
235The Configure options enabling the use of threads and the use of
23664-bitness are now more daring in the sense that they no more have
237an explicit list of operating systems of known threads/64-bit
238capabilities. In other words: if your operating system has the
239necessary APIs, you should be able just to go ahead and use them.
240See also L<"64-bit support">.
241
242=head2 Long Doubles
243
244Some platforms have "long doubles", floating point numbers of even
437784d6 245larger range than ordinary "doubles". To enable using long doubles for
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246Perl's scalars, use -Duselongdouble.
247
248=head2 -Dusemorebits
249
250You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
251See also L<"64-bit support">.
252
253=head2 -Duselargefiles
254
255Some platforms support large files, files larger than two gigabytes.
256See L<"Large file support"> for more information.
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257
258=head2 installusrbinperl
259
260You can use "Configure -Uinstallusrbinperl" which causes installperl
261to skip installing perl also as /usr/bin/perl. This is useful if you
262prefer not to modify /usr/bin for some reason or another but harmful
263because many scripts assume to find Perl in /usr/bin/perl.
264
265=head2 SOCKS support
266
267You can use "Configure -Dusesocks" which causes Perl to probe
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268for the SOCKS (v5, not v4) proxy protocol library,
269http://www.socks.nec.com/
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270
271=head2 C<-A> flag
272
273You can "post-edit" the Configure variables using the Configure C<-A>
274flag. The editing happens immediately after the platform specific
275hints files have been processed but before the actual configuration
276process starts. Run C<Configure -h> to find out the full C<-A> syntax.
277
c35dd67d 278=head2 Enhanced Installation Directories
67d3893f 279
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280The installation structure has been enriched to improve the support for
281maintaining multiple versions of perl, to provide locations for
282vendor-supplied modules and scripts, and to ease maintenance of
283locally-added modules and scripts. See the section on Installation
284Directories in the INSTALL file for complete details. For most users
285building and installing from source, the defaults should be fine.
67d3893f 286
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287=head1 Core Changes
288
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289=head2 Unicode and UTF-8 support
290
291Perl can optionally use UTF-8 as its internal representation for character
a5222a85 292strings. The C<utf8> pragma enables this support in the current lexical
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293scope. See L<utf8> for more information.
294
295=head2 Lexically scoped warning categories
296
297You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 298level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 299for details.
9d73390d 300
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301=head2 Lvalue subroutines
302
303WARNING: This is an experimental feature.
304
305change#4081
306[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
307Tuomas Lukka <lukka@fas.harvard.edu>)]
308
309=head2 "our" declarations
310
311An "our" declaration introduces a value that can be best understood
312as a lexically scoped symbolic alias to a global variable in the
313current package. This is mostly useful as an alternative to the
314C<vars> pragma, but also provides the opportunity to introduce
315typing and other attributes for such variables. See L<perlfunc/our>.
316
317=head2 Weak references
318
319WARNING: This is an experimental feature.
320
321change#3385, also need perlguts documentation
322
323[TODO - Tuomas Lukka <lukka@fas.harvard.edu>]
324
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325=head2 File globbing implemented internally
326
327WARNING: This is currently an experimental feature. Interfaces and
328implementation are likely to change.
329
330Perl can be compiled with -DPERL_INTERNAL_GLOB to use the File::Glob
331implementation of the glob() operator. This avoids using an external
332csh process and the problems associated with it.
333
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334=head2 Binary numbers supported
335
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336Binary numbers are now supported as literals, in s?printf formats, and
337C<oct()>:
338
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339 $answer = 0b101010;
340 printf "The answer is: %b\n", oct("0b101010");
4f19785b 341
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342=head2 Some arrows may be omitted in calls through references
343
344Perl now allows the arrow to be omitted in many constructs
345involving subroutine calls through references. For example,
346C<$foo[10]->('foo')> may now be written C<$foo[10]('foo')>.
347This is rather similar to how the arrow may be omitted from
348C<$foo[10]->{'foo'}>. Note however, that the arrow is still
349required for C<foo(10)->('bar')>.
350
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351=head2 syswrite() ease-of-use
352
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353The length argument of C<syswrite()> has become optional.
354
355=head2 Filehandles can be autovivified
356
357The construct C<open(my $fh, ...)> can be used to create filehandles
358more easily. The filehandle will be automatically closed at the end
359of the scope of $fh, provided there are no other references to it. This
360largely eliminates the need for typeglobs when opening filehandles
361that must be passed around, as in the following example:
362
363 sub myopen {
364 open my $fh, "@_"
365 or die "Can't open '@_': $!";
366 return $fh;
367 }
368
369 {
370 my $f = myopen("</etc/motd");
371 print <$f>;
372 # $f implicitly closed here
373 }
374
375[TODO - this idiom needs more pod penetration]
6c67e1bb 376
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377=head2 64-bit support
378
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379All platforms that have 64-bit integers either (a) natively as longs
380or ints (b) via special compiler flags (c) using long long are able to
381use "quads" (64-integers) as follows:
382
383=over 4
384
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385=item *
386
387constants (decimal, hexadecimal, octal, binary) in the code
388
389=item *
9c107f78 390
a5222a85 391arguments to oct() and hex()
9c107f78 392
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393=item *
394
395arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
396
397=item *
9c107f78 398
a5222a85 399printed as such
9c107f78 400
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401=item *
402
403pack() and unpack() "q" and "Q" formats
404
405=item *
406
407in basic arithmetics: + - * / %
408
409=item *
1fad5d67 410
a5222a85 411vec() (but see the below note about bit arithmetics)
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412
413=back
414
415Note that unless you have the case (a) you will have to configure
416and compile Perl using the -Duse64bits Configure flag.
417
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418Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
41964-bit clean, they are explictly forced to be 32-bit. Bit arithmetics
420for bit vectors (created by vec()) are not limited in their width.
d0ba1bd2 421
2d4389e4 422Last but not least: note that due to Perl's habit of always using
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423floating point numbers the quads are still not true integers.
424When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
425-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
426are silently promoted to floating point numbers, after which they will
427start losing precision (their lower digits).
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428
429=head2 Large file support
430
431If you have filesystems that support "large files" (files larger than
aa855319 4322 gigabytes), you may now also be able to create and access them from
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433Perl. You have to use Configure -Duselargefiles. Turning on the
434large file support turns on also the 64-bit support, for obvious reasons.
2d4389e4 435
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436Note that in addition to requiring a proper file system to do large
437files you may also need to adjust your per-process (or your
438per-system, or per-process-group, or per-user-group) maximum filesize
439limits before running Perl scripts that try to handle large files,
440especially if you intend to write such files.
441
442Finally, in addition to your process/process group maximum filesize
443limits, you may have quota limits on your filesystems that stop you
444(your user id or your user group id) from using large files.
445
446Adjusting your process/user/group/file system/operating system limits
447is outside the scope of Perl core language. For process limits, you
448may try increasing the limits using your shell's limits/limit/ulimit
449command before running Perl. The BSD::Resource extension (not
450included with the standard Perl distribution) may also be of use, it
451offers the getrlimit/setrlimit interface that can be used to adjust
452process resource usage limits, including the maximum filesize limit.
2d4389e4 453
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454=head2 Long doubles
455
456In some systems you may be able to use long doubles to enhance the
457range of precision of your double precision floating point numbers
458(that is, Perl's numbers). Use Configure -Duselongdouble to enable
459this support (if it is available).
460
461=head2 "more bits"
462
463You can Configure -Dusemorebits to turn on both the 64-bit support
464and the long double support.
09bef843 465
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466=head2 Better syntax checks on parenthesized unary operators
467
468Expressions such as:
469
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470 print defined(&foo,&bar,&baz);
471 print uc("foo","bar","baz");
472 undef($foo,&bar);
62c18ce2 473
7711098a 474used to be accidentally allowed in earlier versions, and produced
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475unpredictable behaviour. Some produced ancillary warnings
476when used in this way; others silently did the wrong thing.
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477
478The parenthesized forms of most unary operators that expect a single
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479argument now ensure that they are not called with more than one
480argument, making the cases shown above syntax errors. The usual
481behaviour of:
62c18ce2 482
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483 print defined &foo, &bar, &baz;
484 print uc "foo", "bar", "baz";
485 undef $foo, &bar;
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486
487remains unchanged. See L<perlop>.
488
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489=head2 POSIX character class syntax [: :] supported
490
491For example to match alphabetic characters use /[[:alpha:]]/.
492See L<perlre> for details.
493
5a929a98 494=head2 Improved C<qw//> operator
8127e0e3 495
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496The C<qw//> operator is now evaluated at compile time into a true list
497instead of being replaced with a run time call to C<split()>. This
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498removes the confusing misbehaviour of C<qw//> in scalar context, which
499had inherited that behaviour from split().
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500
501Thus:
502
503 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
504
505now correctly prints "3|a", instead of "2|a".
8127e0e3 506
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507=head2 pack() format 'Z' supported
508
509The new format type 'Z' is useful for packing and unpacking null-terminated
510strings. See L<perlfunc/"pack">.
511
4d0c1c44 512=head2 pack() format modifier '!' supported
ee3907e2 513
14218588 514The new format type modifier '!' is useful for packing and unpacking
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515native shorts, ints, and longs. See L<perlfunc/"pack">.
516
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517=head2 pack() and unpack() support counted strings
518
a5222a85 519The template character '/' can be used to specify a counted string
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520type to be packed or unpacked. See L<perlfunc/"pack">.
521
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522=head2 Comments in pack() templates
523
524The '#' character in a template introduces a comment up to
525end of the line. This facilitates documentation of pack()
526templates.
527
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528=head2 $^X variables may now have names longer than one character
529
530Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
531error. Now variable names that begin with a control character may be
532arbitrarily long. However, for compatibility reasons, these variables
533I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 534C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
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535than one control character, such as C<${^XY^Z}>, are illegal.
536
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537The old syntax has not changed. As before, `^X' may be either a
538literal control-X character or the two-character sequence `caret' plus
539`X'. When braces are omitted, the variable name stops after the
2b92dfce 540control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 541C<$^X . "YZ"> as before.
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542
543As before, lexical variables may not have names beginning with control
544characters. As before, variables whose names begin with a control
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545character are always forced to be in package `main'. All such variables
546are reserved for future extensions, except those that begin with
09bef843 547C<^_>, which may be used by user programs and are guaranteed not to
14218588 548acquire special meaning in any future version of Perl.
2b92dfce 549
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550=head2 C<use attrs> implicit in subroutine attributes
551
552Formerly, if you wanted to mark a subroutine as being a method call or
553as requiring an automatic lock() when it is entered, you had to declare
554that with a C<use attrs> pragma in the body of the subroutine.
555That can now be accomplished with a declaration syntax, like this:
556
557 sub mymethod : locked, method ;
558 ...
559 sub mymethod : locked, method {
560 ...
561 }
562
563F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
564with the stubs they provide. See L<attributes>.
565
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566=head2 Regular expression improvements
567
568change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
569[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
570
571=head2 Overloading improvements
572
573change#2150
574[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
575
576=head2 open() with more than two arguments
577
578[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
579
580=head2 Support for interpolating named characters
581
582change#4052
583[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
584
08cd8952 585=head2 Experimental support for user-hooks in @INC
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586
587[TODO - Ken Fox <kfox@ford.com>]
588
589=head2 C<require> and C<do> may be overridden
590
591C<require> and C<do 'file'> operations may be overridden locally
592by importing subroutines of the same name into the current package
593(or globally by importing them into the CORE::GLOBAL:: namespace).
594Overriding C<require> will also affect C<use>, provided the override
595is visible at compile-time.
596See L<perlsub/"Overriding Built-in Functions">.
597
598=head2 New variable $^C reflects C<-c> switch
599
08cd8952 600C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
601in compile-only mode (i.e. via the C<-c> switch). Since
602BEGIN blocks are executed under such conditions, this variable
603enables perl code to determine whether actions that make sense
604only during normal running are warranted. See L<perlvar>.
605
606=head2 Optional Y2K warnings
607
608If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
609it emits optional warnings when concatenating the number 19
610with another number.
611
612This behavior must be specifically enabled when running Configure.
613See L<INSTALL> and L<README.Y2K>.
614
fbad3eb5
GS
615=head1 Significant bug fixes
616
617=head2 E<lt>HANDLEE<gt> on empty files
618
619With C<$/> set to C<undef>, slurping an empty file returns a string of
14218588
GS
620zero length (instead of C<undef>, as it used to) the first time the
621HANDLE is read. Further reads yield C<undef>.
fbad3eb5
GS
622
623This means that the following will append "foo" to an empty file (it used
14218588 624to do nothing):
fbad3eb5
GS
625
626 perl -0777 -pi -e 's/^/foo/' empty_file
627
14218588 628The behaviour of:
fbad3eb5
GS
629
630 perl -pi -e 's/^/foo/' empty_file
631
632is unchanged (it continues to leave the file empty).
633
0244c3a4
GS
634=head2 C<eval '...'> improvements
635
636Line numbers (as reflected by caller() and most diagnostics) within
637C<eval '...'> were often incorrect when here documents were involved.
638This has been corrected.
639
640Lexical lookups for variables appearing in C<eval '...'> within
641functions that were themselves called within an C<eval '...'> were
14218588
GS
642searching the wrong place for lexicals. The lexical search now
643correctly ends at the subroutine's block boundary.
0244c3a4
GS
644
645Parsing of here documents used to be flawed when they appeared as
646the replacement expression in C<eval 's/.../.../e'>. This has
647been fixed.
648
a5222a85
GS
649=head2 All compilation errors are true errors
650
651Some "errors" encountered at compile time were by neccessity
652generated as warnings followed by eventual termination of the
653program. This enabled more such errors to be reported in a
654single run, rather than causing a hard stop at the first error
655that was encountered.
656
657The mechanism for reporting such errors has been reimplemented
658to queue compile-time errors and report them at the end of the
659compilation as true errors rather than as warnings. This fixes
08cd8952
GS
660cases where error messages leaked through in the form of warnings
661when code was compiled at run time using C<eval STRING>, and
662also allows such errors to be reliably trapped using __DIE__ hooks.
a5222a85 663
45bc9206
GS
664=head2 Automatic flushing of output buffers
665
14218588
GS
666fork(), exec(), system(), qx//, and pipe open()s now flush buffers
667of all files opened for output when the operation
668was attempted. This mostly eliminates confusing
45bc9206 669buffering mishaps suffered by users unaware of how Perl internally
14218588 670handles I/O.
45bc9206 671
af8c498a
GS
672=head2 Better diagnostics on meaningless filehandle operations
673
674Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
675are compile time errors. Attempting to read from filehandles that
676were opened only for writing will now produce warnings (just as
677writing to read-only filehandles does).
678
a5222a85
GS
679=head2 Where possible, buffered data discarded from duped input filehandle
680
681C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
682was previously read and buffered in C<OLD> before duping the handle.
683On platforms where doing this is allowed, the next read operation
684on C<NEW> will return the same data as the corresponding operation
685on C<OLD>. Formerly, it would have returned the data from the start
686of the following disk block instead.
687
688=head2 system(), backticks and pipe open now reflect exec() failure
689
690On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
691etc., are implemented via fork() and exec(). When the underlying
692exec() fails, earlier versions did not report the error properly,
693since the exec() happened to be in a different process.
694
695The child process now communicates with the parent about the
437784d6 696error in launching the external command, which allows these
a5222a85
GS
697constructs to return with their usual error value and set $!.
698
699=head2 Implicitly closed filehandles are safer
700
701Sometimes implicitly closed filehandles (as when they are localized,
702and Perl automatically closes them on exiting the scope) could
703inadvertently set $? or $!. This has been corrected.
704
705=head2 C<(\$)> prototype and C<$foo{a}>
706
707An scalar reference prototype now correctly allows a hash or
708array element in that slot.
709
710=head2 Pseudo-hashes work better
711
712Dereferencing some types of reference values in a pseudo-hash,
713such as C<$ph->{foo}[1]>, was accidentally disallowed. This has
714been corrected.
715
716When applied to a pseudo-hash element, exists() now reports whether
717the specified value exists, not merely if the key is valid.
718
719=head2 C<goto &sub> and AUTOLOAD
720
08cd8952 721The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
722to be autoloaded.
723
724=head2 C<-bareword> allowed under C<use integer>
725
726The autoquoting of barewords preceded by C<-> did not work
727in prior versions when the C<integer> pragma was enabled.
728This has been fixed.
729
730=head2 Boolean assignment operators are legal lvalues
731
732Constructs such as C<($a ||= 2) += 1> are now allowed.
733
734=head2 C<sort $coderef @foo> allowed
735
736sort() did not accept a subroutine reference as the comparison
08cd8952 737function in earlier versions. This is now permitted.
a5222a85
GS
738
739=head2 Failures in DESTROY()
740
741When code in a destructor threw an exception, it went unnoticed
742in earlier versions of Perl, unless someone happened to be
743looking in $@ just after the point the destructor happened to
744run. Such failures are now visible as warnings when warnings are
745enabled.
746
747=head2 Locale bugs fixed
54195c32 748
437784d6 749printf() and sprintf() previously reset the numeric locale
67d3893f
JH
750back to the default "C" locale. This has been fixed.
751
752Numbers formatted according to the local numeric locale
753(such as using a decimal comma instead of a decimal dot) caused
754"isn't numeric" warnings, even while the operations accessing
755those numbers produced correct results. The warnings are gone.
54195c32 756
a5222a85
GS
757=head2 Memory leaks
758
759The C<eval 'return sub {...}'> construct could sometimes leak
760memory. This has been fixed.
761
762Operations that aren't filehandle constructors used to leak memory
763when used on invalid filehandles. This has been fixed.
764
765Constructs that modified C<@_> could fail to deallocate values
766in C<@_> and thus leak memory. This has been corrected.
767
768=head2 Spurious subroutine stubs after failed subroutine calls
769
770Perl could sometimes create empty subroutine stubs when a
771subroutine was not found in the package. Such cases stopped
772later method lookups from progressing into base packages.
773This has been corrected.
774
775=head2 Consistent numeric conversions
776
777change#3378,3318
778[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
779
780=head2 Taint failures under C<-U>
781
782When running in unsafe mode, taint violations could sometimes
783cause silent failures. This has been fixed.
784
785=head2 END blocks and the C<-c> switch
786
787Prior versions used to run BEGIN B<and> END blocks when Perl was
788run in compile-only mode. Since this is typically not the expected
08cd8952 789behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
790is used.
791
792Note that something resembling the previous behavior can still be
793obtained by putting C<BEGIN { $^C = 0; exit; } at the very end of
794the top level source file.
795
796=head2 Potential to leak DATA filehandles
797
798Using the C<__DATA__> token creates an implicit filehandle to
799the file that contains the token. It is the program's
800responsibility to close it when it is done reading from it.
801
802This caveat is now better explained in the documentation.
803See L<perldata>.
804
805=head2 Diagnostics follow STDERR
806
807Diagnostic output now goes to whichever file the C<STDERR> handle
808is pointing at, instead of always going to the underlying C runtime
809library's C<stderr>.
810
811=head2 Other fixes for better diagnostics
812
437784d6 813Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
814during the global destruction phase.
815
816Diagnostics emitted from code running in threads other than the main
817thread are now accompanied by the thread ID.
818
819Embedded null characters in diagnostics now actually show up. They
820used to truncate the message in prior versions.
821
822$foo::a and $foo::b are now exempt from "possible typo" warnings only
823if sort() is encountered in package foo.
824
501fbaef 825Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
826constructs now generate a warning, since they may take on new
827semantics in later versions of Perl.
828
829=head1 Performance enhancements
830
831=head2 Simple sort() using { $a <=> $b } and the like are optimized
832
08cd8952 833Many common sort() operations using a simple inlined block are now
a5222a85
GS
834optimized for faster performance.
835
836=head2 Optimized assignments to lexical variables
837
838Certain operations in the RHS of assignment statements have been
839optimized to directly set the lexical variable on the LHS,
840eliminating redundant copying overheads.
841
842=head2 Method lookups optimized
843
844[TODO - Chip Salzenberg <chip@perlsupport.com>]
845
846=head2 Faster mechanism to invoke XSUBs
847
848change#4044,4125
849[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
850
851=head2 Perl_malloc() improvements
852
853change#4237
854[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
855
856=head2 Faster subroutine calls
857
858Minor changes in how subroutine calls are handled internally
859provide marginal improvements in performance.
860
861=head1 Platform specific changes
862
863=head2 Additional supported platforms
ba8251e8 864
5fdc711f
GS
865=over 4
866
867=item *
868
6c67e1bb
TC
869VM/ESA is now supported.
870
5fdc711f
GS
871=item *
872
ee3907e2
JH
873Siemens BS2000 is now supported under the POSIX Shell.
874
875=item *
876
2bb14304
JH
877The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
878extension.
6c67e1bb 879
5fdc711f
GS
880=item *
881
ee3907e2 882GNU/Hurd is now supported.
6c67e1bb 883
00ad96e1
JH
884=item *
885
886Rhapsody is now supported.
887
27806c82
JH
888=item *
889
890EPOC is is now supported (on Psion 5).
891
5fdc711f
GS
892=back
893
a5222a85
GS
894=head2 DOS
895
896[TODO - Laszlo Molnar <laszlo.molnar@eth.ericsson.se>]
897
898=head2 OS/2
899
900[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
901
902=head2 VMS
903
904[TODO - Charles Bailey <bailey@newman.upenn.edu>]
905
906=head2 Win32
907
908Site library searches failed to look for ".../site/5.XXX/lib"
909if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
910
911When given a pathname that consists only of a drivename, such
912as C<A:>, opendir() and stat() now use the current working
913directory for the drive rather than the drive root.
914
915The builtin XSUB functions in the Win32:: namespace are
916documented. See L<Win32>.
917
918$^X now contains the full path name of the running executable.
919
920A Win32::GetLongPathName() function is provided to complement
921Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
922
923POSIX::uname() is supported.
924
925system(1,...) now returns true process IDs rather than process
926handles. kill() accepts any real process id, rather than strictly
927return values from system(1,...).
928
929The C<Shell> module is supported.
930
883d36a6
GS
931Rudimentary support for building under command.com in Windows 95
932has been added.
933
a5222a85
GS
934[TODO - GSAR]
935
6c67e1bb
TC
936=head1 New tests
937
938=over 4
939
09bef843
SB
940=item lib/attrs
941
942Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
943
944=item lib/io_const
6c67e1bb
TC
945
946IO constants (SEEK_*, _IO*).
14218588 947
09bef843 948=item lib/io_dir
6c67e1bb
TC
949
950Directory-related IO methods (new, read, close, rewind, tied delete).
951
09bef843 952=item lib/io_multihomed
6c67e1bb
TC
953
954INET sockets with multi-homed hosts.
955
09bef843 956=item lib/io_poll
6c67e1bb
TC
957
958IO poll().
959
09bef843 960=item lib/io_unix
6c67e1bb
TC
961
962UNIX sockets.
963
09bef843
SB
964=item op/attrs
965
966Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
967
6c67e1bb
TC
968=item op/filetest
969
970File test operators.
971
972=item op/lex_assign
973
5fdc711f 974Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb
TC
975
976=back
e02fdbd2 977
ba8251e8
GS
978=head1 Modules and Pragmata
979
3e8c4fa0
JH
980=head2 Modules
981
b7d8191e
JH
982=over 4
983
09bef843
SB
984=item attributes
985
986While used internally by Perl as a pragma, this module also
987provides a way to fetch subroutine and variable attributes.
988See L<attributes>.
989
a5222a85
GS
990=item B
991
501fbaef
GS
992The Perl Compiler suite has been extensively reworked for this
993release.
994
a5222a85
GS
995[TODO - Vishal Bhatia <vishal@gol.com>,
996Nick Ing-Simmons <nick@ni-s.u-net.com>]
997
f29c64d6
GS
998=item ByteLoader
999
a5222a85 1000The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1001Perl bytecode. See L<ByteLoader>.
1002
a5222a85
GS
1003=item constant
1004
1005References can now be used. See L<constant>.
1006
1007=item charnames
1008
1009change#4052
1010[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1011
1012=item Data::Dumper
1013
1014A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1015too deeply into deep data structures. See L<Data::Dumper>.
a5222a85
GS
1016
1017Dumping C<qr//> objects works correctly.
1018
1019=item DB
1020
1021C<DB> is an experimental module that exposes a clean abstraction
1022to Perl's debugging API.
1023
1024=item DB_File
1025
1026[TODO - Paul Marquess <paul.marquess@bt.com>]
1027
f29c64d6
GS
1028=item Devel::DProf
1029
a5222a85 1030Devel::DProf, a Perl source code profiler has been added. See L<DProf>.
f29c64d6 1031
b7d8191e
JH
1032=item Dumpvalue
1033
437784d6 1034The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1035
1036=item Benchmark
1037
54e82ce5
GS
1038Overall, Benchmark results exhibit lower average error and better timing
1039accuracy.
1040
868cb350 1041You can now run tests for I<n> seconds instead of guessing the right
14218588
GS
1042number of tests to run: e.g. timethese(-5, ...) will run each
1043code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1044means "for at least 3 CPU seconds". The output format has also
14218588 1045changed. For example:
155776c0 1046
54e82ce5 1047 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1048
1049will now output something like this:
1050
54e82ce5
GS
1051 Benchmark: running a, b, each for at least 5 CPU seconds...
1052 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1053 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1054
1055New features: "each for at least N CPU seconds...", "wallclock secs",
1056and the "@ operations/CPU second (n=operations)".
b7d8191e 1057
54e82ce5
GS
1058timethese() now returns a reference to a hash of Benchmark objects containing
1059the test results, keyed on the names of the tests.
1060
1061timethis() now returns the iterations field in the Benchmark result object
1062instead of 0.
1063
1064timethese(), timethis(), and the new cmpthese() (see below) can also take
1065a format specifier of 'none' to suppress output.
1066
1067A new function countit() is just like timeit() except that it takes a
1068TIME instead of a COUNT.
1069
1070A new function cmpthese() prints a chart comparing the results of each test
1071returned from a timethese() call. For each possible pair of tests, the
1072percentage speed difference (iters/sec or seconds/iter) is shown.
1073
1074For other details, see L<Benchmark>.
a5222a85 1075
f505c983
GS
1076=item Devel::Peek
1077
1078The Devel::Peek module provides access to the internal representation
14218588 1079of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1080
a5222a85
GS
1081=item ExtUtils::MakeMaker
1082
1083change#4135, also needs docs in module pod
1084[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1085
b7d8191e
JH
1086=item Fcntl
1087
1088More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
14218588 1089large (more than 4G) file access (64-bit support is not yet
b7d8191e
JH
1090working, though, so no need to get overly excited), Free/Net/OpenBSD
1091locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
1092O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
1093
a5222a85
GS
1094=item File::Compare
1095
1096A compare_text() function has been added, which allows custom
1097comparison functions. See L<File::Compare>.
1098
1099=item File::Find
1100
1101File::Find now works correctly when the wanted() function is either
1102autoloaded or is a symbolic reference.
1103
08cd8952 1104A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1105when pruning top-level directories has been fixed.
1106
becf2bd3
GS
1107=item File::Glob
1108
1109This extension implements BSD-style file globbing. It will also be
1110used for the internal implementation of the glob() operator if
1111Perl was compiled with -DPERL_INTERNAL_GLOB. See L<File::Glob>.
1112
f505c983
GS
1113=item File::Spec
1114
1115New methods have been added to the File::Spec module: devnull() returns
19799a22 1116the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1117the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1118to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1119rel2abs(). For compatibility with operating systems that specify volume
1120names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1121have been added.
1122
1123=item File::Spec::Functions
1124
1125The new File::Spec::Functions modules provides a function interface
14218588 1126to the File::Spec module. Allows shorthand
f505c983 1127
14218588 1128 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1129
1130instead of
1131
14218588 1132 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1133
a5222a85
GS
1134=item Getopt::Long
1135
c6edd1b7
GS
1136Getopt::Long licensing has changed to allow the Perl Artistic License
1137as well as the GPL. It used to be GPL only, which got in the way of
1138non-GPL applications that wanted to use Getopt::Long.
1139
1140Getopt::Long encourages the use of Pod::Usage to produce help
1141messages. For example:
1142
1143 use Getopt::Long;
1144 use Pod::Usage;
1145 my $man = 0;
1146 my $help = 0;
1147 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1148 pod2usage(1) if $help;
1149 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1150
1151 __END__
1152
1153 =head1 NAME
1154
1155 sample - Using GetOpt::Long and Pod::Usage
1156
1157 =head1 SYNOPSIS
1158
1159 sample [options] [file ...]
1160
1161 Options:
1162 -help brief help message
1163 -man full documentation
1164
1165 =head1 OPTIONS
1166
1167 =over 8
1168
1169 =item B<-help>
1170
1171 Print a brief help message and exits.
1172
1173 =item B<-man>
1174
1175 Prints the manual page and exits.
1176
1177 =back
1178
1179 =head1 DESCRIPTION
1180
1181 B<This program> will read the given input file(s) and do someting
1182 useful with the contents thereof.
1183
1184 =cut
1185
1186See L<Pod::Usage> for details.
1187
1188A bug that prevented the non-option call-back E<lt>E<gt> from being
1189specified as the first argument has been fixed.
1190
1191To specify the characters E<lt> and E<gt> as option starters, use
1192E<gt>E<lt>. Note, however, that changing option starters is strongly
1193deprecated.
a5222a85
GS
1194
1195=item IO
1196
1197write() and syswrite() will now accept a single-argument
1198form of the call, for consistency with Perl's syswrite().
1199
1200You can now create a TCP-based IO::Socket::INET without forcing
1201a connect attempt. This allows you to configure its options
1202(like making it non-blocking) and then call connect() manually.
1203
1204A bug that prevented the IO::Socket::protocol() accessor
1205from ever returning the correct value has been corrected.
1206
1207=item JPL
1208
1209Java Perl Lingo is now distributed with Perl. See jpl/README
1210for more information.
1211
883d36a6
GS
1212=item lib
1213
1214C<use lib> now weeds out any trailing duplicate entries.
1215C<no lib> removes all named entries.
1216
e16b8f49
WM
1217=item Math::BigInt
1218
437784d6 1219The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
e16b8f49
WM
1220and C<~> are now supported on bigints.
1221
b7d8191e 1222=item Math::Complex
7711098a 1223
14218588 1224The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1225act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e
JH
1226
1227=item Math::Trig
1228
14218588
GS
1229A little bit of radial trigonometry (cylindrical and spherical),
1230radial coordinate conversions, and the great circle distance were added.
b7d8191e 1231
a5222a85
GS
1232=item Pod::Parser
1233
1234[TODO - Brad Appleton <bradapp@enteract.com>]
1235
1236=item Pod::Text and Pod::Man
1237
1238[TODO - Russ Allbery <rra@stanford.edu>]
1239
f4b9d880
RA
1240=item SDBM_File
1241
1242An EXISTS method has been added to this module (and sdbm_exists() has
1243been added to the underlying sdbm library), so one can now call exists
14218588 1244on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1245runtime error.
1246
a5222a85
GS
1247A bug that may have caused data loss when more than one disk block
1248happens to be read from the database in a single FETCH() has been
1249fixed.
1250
06ef4121
PC
1251=item Time::Local
1252
1253The timelocal() and timegm() functions used to silently return bogus
437784d6 1254results when the date fell outside the machine's integer range. They
a5222a85 1255now consistently croak() if the date falls in an unsupported range.
06ef4121 1256
8fe0a5c4
JD
1257=item Win32
1258
1259The error return value in list context has been changed for all functions
14218588
GS
1260that return a list of values. Previously these functions returned a list
1261with a single element C<undef> if an error occurred. Now these functions
1262return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1263functions:
1264
14218588
GS
1265 Win32::FsType
1266 Win32::GetOSVersion
8fe0a5c4
JD
1267
1268The remaining functions are unchanged and continue to return C<undef> on
1269error even in list context.
1270
1271The Win32::SetLastError(ERROR) function has been added as a complement
1272to the Win32::GetLastError() function.
1273
1274The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1275pathname for FILENAME in scalar context. In list context it returns
1276a two-element list containing the fully qualified directory name and
501fbaef 1277the filename. See L<Win32>.
8fe0a5c4 1278
9fe6733a
PM
1279=item DBM Filters
1280
1281A new feature called "DBM Filters" has been added to all the
14218588
GS
1282DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1283DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1284
1285 filter_store_key
1286 filter_store_value
1287 filter_fetch_key
1288 filter_fetch_value
1289
14218588 1290These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1291written to the database or just after they are read from the database.
1292See L<perldbmfilter> for further information.
1293
b7d8191e 1294=back
3e8c4fa0
JH
1295
1296=head2 Pragmata
1297
437784d6 1298C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1299backward-compatibility. It's been replaced by the C<sub : attributes>
1300syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1301
14218588 1302C<use utf8> to enable UTF-8 and Unicode support.
43165c05
GS
1303
1304C<use caller 'encoding'> allows modules to inherit pragmatic attributes
1305from the caller's context. C<encoding> is currently the only supported
1306attribute.
9d73390d 1307
4438c4b7 1308Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1309See L<perllexwarn>.
6c67e1bb 1310
67d3893f
JH
1311C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1312...). Currently only one subpragma implemented, "use filetest
1313'access';", that uses access(2) or equivalent to check permissions
1314instead of using stat(2) as usual. This matters in filesystems
1315where there are ACLs (access control lists): the stat(2) might lie,
1316but access(2) knows better.
6c67e1bb 1317
ba8251e8
GS
1318=head1 Utility Changes
1319
a5222a85
GS
1320=head2 h2ph
1321
1322[TODO - Kurt Starsinic <kstar@chapin.edu>]
1323
1324=head2 perlcc
1325
1326C<perlcc> now supports the C and Bytecode backends. By default,
1327it generates output from the simple C backend rather than the
1328optimized C backend.
1329
1330Support for non-Unix platforms has been improved.
1331
1332=head2 h2xs
1333
1334change#4232
1335[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
e02fdbd2 1336
ba8251e8
GS
1337=head1 Documentation Changes
1338
5fdc711f
GS
1339=over 4
1340
883d36a6
GS
1341=item perlcompile.pod
1342
1343An introduction to using the Perl Compiler suite.
1344
1345=item perlhack.pod
1346
1347Some guidelines for hacking the Perl source code.
1348
5fdc711f 1349=item perlopentut.pod
f8284313 1350
5fdc711f
GS
1351A tutorial on using open() effectively.
1352
1353=item perlreftut.pod
1354
1355A tutorial that introduces the essentials of references.
1356
14218588
GS
1357=item perltootc.pod
1358
1359A tutorial on managing class data for object modules.
1360
5fdc711f 1361=back
e02fdbd2 1362
73b437c8 1363=head1 New or Changed Diagnostics
ba8251e8 1364
a99ba403
GS
1365=over 4
1366
09bef843
SB
1367=item "my sub" not yet implemented
1368
1369(F) Lexically scoped subroutines are not yet implemented. Don't try that
1370yet.
1371
a99ba403
GS
1372=item '!' allowed only after types %s
1373
1374(F) The '!' is allowed in pack() and unpack() only after certain types.
1375See L<perlfunc/pack>.
1376
1377=item / cannot take a count
1378
1379(F) You had an unpack template indicating a counted-length string,
1380but you have also specified an explicit size for the string.
1381See L<perlfunc/pack>.
1382
1383=item / must be followed by a, A or Z
1384
1385(F) You had an unpack template indicating a counted-length string,
1386which must be followed by one of the letters a, A or Z
1387to indicate what sort of string is to be unpacked.
1388See L<perlfunc/pack>.
1389
1390=item / must be followed by a*, A* or Z*
1391
437784d6 1392(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1393Currently the only things that can have their length counted are a*, A* or Z*.
1394See L<perlfunc/pack>.
1395
1396=item / must follow a numeric type
1397
1398(F) You had an unpack template that contained a '#',
1399but this did not follow some numeric unpack specification.
1400See L<perlfunc/pack>.
1401
1402=item Repeat count in pack overflows
1403
1404(F) You can't specify a repeat count so large that it overflows
1405your signed integers. See L<perlfunc/pack>.
1406
1407=item Repeat count in unpack overflows
1408
1409(F) You can't specify a repeat count so large that it overflows
1410your signed integers. See L<perlfunc/unpack>.
1411
1412=item /%s/: Unrecognized escape \\%c passed through
1413
1414(W) You used a backslash-character combination which is not recognized
1415by Perl. This combination appears in an interpolated variable or a
1416C<'>-delimited regular expression.
1417
1418=item /%s/ should probably be written as "%s"
1419
1420(W) You have used a pattern where Perl expected to find a string,
437784d6 1421as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
1422or false result of matching the pattern against $_ as the string,
1423which is probably not what you had in mind.
1424
1425=item %s() called too early to check prototype
1426
1427(W) You've called a function that has a prototype before the parser saw a
1428definition or declaration for it, and Perl could not check that the call
1429conforms to the prototype. You need to either add an early prototype
1430declaration for the subroutine in question, or move the subroutine
1431definition ahead of the call to get proper prototype checking. Alternatively,
1432if you are certain that you're calling the function correctly, you may put
1433an ampersand before the name to avoid the warning. See L<perlsub>.
1434
09bef843
SB
1435=item %s package attribute may clash with future reserved word: %s
1436
1437(W) A lowercase attribute name was used that had a package-specific handler.
1438That name might have a meaning to Perl itself some day, even though it
1439doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1440See L<attributes>.
1441
a99ba403 1442=item (in cleanup) %s
6b121555 1443
a99ba403
GS
1444(W) This prefix usually indicates that a DESTROY() method raised
1445the indicated exception. Since destructors are usually called by
1446the system at arbitrary points during execution, and often a vast
1447number of times, the warning is issued only once for any number
1448of failures that would otherwise result in the same message being
1449repeated.
1450
1451Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1452could also result in this warning. See L<perlcall/G_KEEPERR>.
1453
1454=item <> should be quotes
1455
1456(F) You wrote C<require E<lt>fileE<gt>> when you should have written
1457C<require 'file'>.
1458
1459=item Attempt to join self
1460
1461(F) You tried to join a thread from within itself, which is an
1462impossible task. You may be joining the wrong thread, or you may
1463need to move the join() to some other thread.
1464
1465=item Bad evalled substitution pattern
1466
1467(F) You've used the /e switch to evaluate the replacement for a
1468substitution, but perl found a syntax error in the code to evaluate,
1469most likely an unexpected right brace '}'.
1470
1471=item Bad realloc() ignored
1472
1473(S) An internal routine called realloc() on something that had never been
1474malloc()ed in the first place. Mandatory, but can be disabled by
1475setting environment variable C<PERL_BADFREE> to 1.
1476
1477=item Binary number > 0b11111111111111111111111111111111 non-portable
1478
1479(W) The binary number you specified is larger than 2**32-1
1480(4294967295) and therefore non-portable between systems. See
1481L<perlport> for more on portability concerns.
1482
1483=item Bit vector size > 32 non-portable
1484
1485(W) Using bit vector sizes larger than 32 is non-portable.
1486
1487=item Buffer overflow in prime_env_iter: %s
1488
1489(W) A warning peculiar to VMS. While Perl was preparing to iterate over
1490%ENV, it encountered a logical name or symbol definition which was too long,
1491so it was truncated to the string shown.
1492
1493=item Can't check filesystem of script "%s"
1494
1495(P) For some reason you can't check the filesystem of the script for nosuid.
1496
1497=item Can't modify non-lvalue subroutine call
1498
437784d6
GS
1499(F) Subroutines meant to be used in lvalue context should be declared as
1500such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
1501
1502=item Can't read CRTL environ
1503
1504(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1505from the CRTL's internal environment array and discovered the array was
1506missing. You need to figure out where your CRTL misplaced its environ
1507or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1508
1509=item Can't remove %s: %s, skipping file
1510
1511(S) You requested an inplace edit without creating a backup file. Perl
1512was unable to remove the original file to replace it with the modified
1513file. The file was left unmodified.
1514
1515=item Can't return %s from lvalue subroutine
1516
1517(F) Perl detected an attempt to return illegal lvalues (such
1518as temporary or readonly values) from a subroutine used as an lvalue.
1519This is not allowed.
1520
1521=item Can't weaken a nonreference
1522
1523(F) You attempted to weaken something that was not a reference. Only
1524references can be weakened.
1525
1526=item Character class [:%s:] unknown
1527
1528(F) The class in the character class [: :] syntax is unknown.
437784d6 1529See L<perlre>.
a99ba403
GS
1530
1531=item Character class syntax [%s] belongs inside character classes
1532
1533(W) The character class constructs [: :], [= =], and [. .] go
1534I<inside> character classes, the [] are part of the construct,
437784d6
GS
1535for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1536are not currently implemented; they are simply placeholders for
1537future extensions.
a99ba403
GS
1538
1539=item Constant is not %s reference
1540
1541(F) A constant value (perhaps declared using the C<use constant> pragma)
1542is being dereferenced, but it amounts to the wrong type of reference. The
1543message indicates the type of reference that was expected. This usually
1544indicates a syntax error in dereferencing the constant value.
1545See L<perlsub/"Constant Functions"> and L<constant>.
1546
1547=item constant(%s): %%^H is not localized
1548
1549(F) When setting compile-time-lexicalized hash %^H one should set the
1550corresponding bit of $^H as well.
1551
1552=item constant(%s): %s
1553
1554(F) Compile-time-substitutions (such as overloaded constants and
1555character names) were not correctly set up.
1556
1557=item defined(@array) is deprecated
1558
1559(D) defined() is not usually useful on arrays because it checks for an
1560undefined I<scalar> value. If you want to see if the array is empty,
1561just use C<if (@array) { # not empty }> for example.
1562
1563=item defined(%hash) is deprecated
1564
1565(D) defined() is not usually useful on hashes because it checks for an
1566undefined I<scalar> value. If you want to see if the hash is empty,
1567just use C<if (%hash) { # not empty }> for example.
1568
1569=item Did not produce a valid header
1570
1571See Server error.
1572
1573=item Document contains no data
1574
1575See Server error.
1576
1577=item entering effective %s failed
1578
1579(F) While under the C<use filetest> pragma, switching the real and
1580effective uids or gids failed.
6b121555 1581
73b437c8
JH
1582=item false [] range "%s" in regexp
1583
1584(W) A character class range must start and end at a literal character, not
1585another character class like C<\d> or C<[:alpha:]>. The "-" in your false
1586range is interpreted as a literal "-". Consider quoting the "-", "\-".
1587See L<perlre>.
1588
af8c498a 1589=item Filehandle %s opened only for output
6b121555 1590
af8c498a 1591(W) You tried to read from a filehandle opened only for writing. If you
437784d6 1592intended it to be a read/write filehandle, you needed to open it with
af8c498a
GS
1593"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
1594you intended only to read from the file, use "E<lt>". See
1595L<perlfunc/open>.
e02fdbd2 1596
a99ba403
GS
1597=item Hexadecimal number > 0xffffffff non-portable
1598
1599(W) The hexadecimal number you specified is larger than 2**32-1
1600(4294967295) and therefore non-portable between systems. See
1601L<perlport> for more on portability concerns.
1602
1603=item Ill-formed CRTL environ value "%s"
1604
1605(W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
1606environ array, and encountered an element without the C<=> delimiter
1607used to spearate keys from values. The element is ignored.
1608
1609=item Ill-formed message in prime_env_iter: |%s|
1610
1611(W) A warning peculiar to VMS. Perl tried to read a logical name
1612or CLI symbol definition when preparing to iterate over %ENV, and
1613didn't see the expected delimiter between key and value, so the
1614line was ignored.
1615
1616=item Illegal binary digit %s
1617
437784d6 1618(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
1619
1620=item Illegal binary digit %s ignored
1621
1622(W) You may have tried to use a digit other than 0 or 1 in a binary number.
1623Interpretation of the binary number stopped before the offending digit.
1624
1625=item Illegal number of bits in vec
1626
1627(F) The number of bits in vec() (the third argument) must be a power of
1628two from 1 to 32 (or 64, if your platform supports that).
1629
1630=item Integer overflow in %s number
1631
1632(W) The hexadecimal, octal or binary number you have specified either
c6edd1b7 1633as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
1634architecture, and has been converted to a floating point number. On a
163532-bit architecture the largest hexadecimal, octal or binary number
1636representable without overflow is 0xFFFFFFFF, 037777777777, or
16370b11111111111111111111111111111111 respectively. Note that Perl
1638transparently promotes all numbers to a floating point representation
1639internally--subject to loss of precision errors in subsequent
1640operations.
1641
09bef843
SB
1642=item Invalid %s attribute: %s
1643
1644The indicated attribute for a subroutine or variable was not recognized
1645by Perl or by a user-supplied handler. See L<attributes>.
1646
1647=item Invalid %s attributes: %s
1648
1649The indicated attributes for a subroutine or variable were not recognized
1650by Perl or by a user-supplied handler. See L<attributes>.
1651
73b437c8
JH
1652=item invalid [] range "%s" in regexp
1653
1654The offending range is now explicitly displayed.
1655
09bef843
SB
1656=item Invalid separator character %s in attribute list
1657
1658(F) Something other than a comma or whitespace was seen between the
1659elements of an attribute list. If the previous attribute
1660had a parenthesised parameter list, perhaps that list was terminated
1661too soon. See L<attributes>.
1662
a99ba403
GS
1663=item Invalid separator character %s in subroutine attribute list
1664
1665(F) Something other than a comma or whitespace was seen between the
1666elements of a subroutine attribute list. If the previous attribute
1667had a parenthesised parameter list, perhaps that list was terminated
1668too soon.
1669
1670=item leaving effective %s failed
1671
1672(F) While under the C<use filetest> pragma, switching the real and
1673effective uids or gids failed.
1674
1675=item Lvalue subs returning %s not implemented yet
1676
1677(F) Due to limitations in the current implementation, array and hash
1678values cannot be returned in subroutines used in lvalue context.
1679See L<perlsub/"Lvalue subroutines">.
1680
1681=item Method %s not permitted
1682
1683See Server error.
1684
1685=item Missing %sbrace%s on \N{}
1686
1687(F) Wrong syntax of character name literal C<\N{charname}> within
1688double-quotish context.
1689
06eaf0bc
GS
1690=item Missing command in piped open
1691
1692(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
1693construction, but the command was missing or blank.
1694
09bef843
SB
1695=item Missing name in "my sub"
1696
1697(F) The reserved syntax for lexically scoped subroutines requires that they
1698have a name with which they can be found.
1699
a99ba403
GS
1700=item no UTC offset information; assuming local time is UTC
1701
1702(S) A warning peculiar to VMS. Perl was unable to find the local
1703timezone offset, so it's assuming that local system time is equivalent
1704to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
1705to translate to the number of seconds which need to be added to UTC to
1706get local time.
1707
1708=item Octal number > 037777777777 non-portable
1709
1710(W) The octal number you specified is larger than 2**32-1 (4294967295)
1711and therefore non-portable between systems. See L<perlport> for more
1712on portability concerns.
1713
1714See also L<perlport> for writing portable code.
1715
1716=item panic: del_backref
1717
1718(P) Failed an internal consistency check while trying to reset a weak
1719reference.
1720
1721=item panic: kid popen errno read
1722
1723(F) forked child returned an incomprehensible message about its errno.
1724
1725=item panic: magic_killbackrefs
1726
1727(P) Failed an internal consistency check while trying to reset all weak
1728references to an object.
1729
1730=item Possible Y2K bug: %s
1731
1732(W) You are concatenating the number 19 with another number, which
1733could be a potential Year 2000 problem.
1734
1735=item Premature end of script headers
1736
1737See Server error.
1738
1739=item realloc() of freed memory ignored
1740
1741(S) An internal routine called realloc() on something that had already
1742been freed.
1743
1744=item Reference is already weak
1745
1746(W) You have attempted to weaken a reference that is already weak.
1747Doing so has no effect.
1748
1749=item setpgrp can't take arguments
1750
1751(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
1752unlike POSIX setpgid(), which takes a process ID and process group ID.
1753
1754=item Strange *+?{} on zero-length expression
1755
1756(W) You applied a regular expression quantifier in a place where it
1757makes no sense, such as on a zero-width assertion.
1758Try putting the quantifier inside the assertion instead. For example,
1759the way to match "abc" provided that it is followed by three
1760repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
1761
1762=item switching effective %s is not implemented
1763
1764(F) While under the C<use filetest> pragma, we cannot switch the
1765real and effective uids or gids.
1766
437784d6 1767=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
1768
1769=item This Perl can't set CRTL environ elements (%s=%s)
1770
1771(W) Warnings peculiar to VMS. You tried to change or delete an element
1772of the CRTL's internal environ array, but your copy of Perl wasn't
1773built with a CRTL that contained the setenv() function. You'll need to
1774rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
1775L<perlvms>) so that the environ array isn't the target of the change to
1776%ENV which produced the warning.
1777
1778=item Unknown open() mode '%s'
1779
437784d6
GS
1780(F) The second argument of 3-argument open() is not among the list
1781of valid modes: C<L<lt>>, C<L<gt>>, C<E<gt>E<gt>>, C<+L<lt>>,
1782C<+L<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|->.
a99ba403
GS
1783
1784=item Unknown process %x sent message to prime_env_iter: %s
1785
1786(P) An error peculiar to VMS. Perl was reading values for %ENV before
1787iterating over it, and someone else stuck a message in the stream of
1788data Perl expected. Someone's very confused, or perhaps trying to
1789subvert Perl's population of %ENV for nefarious purposes.
1790
af8c498a
GS
1791=item Unrecognized escape \\%c passed through
1792
1793(W) You used a backslash-character combination which is not recognized
1794by Perl.
1795
09bef843
SB
1796=item Unterminated attribute parameter in attribute list
1797
1798(F) The lexer saw an opening (left) parenthesis character while parsing an
1799attribute list, but the matching closing (right) parenthesis
1800character was not found. You may need to add (or remove) a backslash
1801character to get your parentheses to balance. See L<attributes>.
1802
1803=item Unterminated attribute list
1804
1805(F) The lexer found something other than a simple identifier at the start
1806of an attribute, and it wasn't a semicolon or the start of a
1807block. Perhaps you terminated the parameter list of the previous attribute
1808too soon. See L<attributes>.
1809
09bef843
SB
1810=item Unterminated attribute parameter in subroutine attribute list
1811
1812(F) The lexer saw an opening (left) parenthesis character while parsing a
1813subroutine attribute list, but the matching closing (right) parenthesis
1814character was not found. You may need to add (or remove) a backslash
1815character to get your parentheses to balance.
1816
1817=item Unterminated subroutine attribute list
1818
1819(F) The lexer found something other than a simple identifier at the start
1820of a subroutine attribute, and it wasn't a semicolon or the start of a
1821block. Perhaps you terminated the parameter list of the previous attribute
1822too soon.
1823
a99ba403 1824=item Value of CLI symbol "%s" too long
eb6e2d6f 1825
a99ba403
GS
1826(W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
1827element from a CLI symbol table, and found a resultant string longer
1828than 1024 characters. The return value has been truncated to 1024
1829characters.
eb6e2d6f 1830
a99ba403 1831=item Version number must be a constant number
ba8251e8 1832
a99ba403
GS
1833(P) The attempt to translate a C<use Module n.n LIST> statement into
1834its equivalent C<BEGIN> block found an internal inconsistency with
1835the version number.
1836
1837=back
27806c82 1838
a5222a85 1839=head1 Obsolete Diagnostics
3175b8cd 1840
a99ba403
GS
1841=over 4
1842
1843=item Character class syntax [: :] is reserved for future extensions
1844
1845(W) Within regular expression character classes ([]) the syntax beginning
1846with "[:" and ending with ":]" is reserved for future extensions.
1847If you need to represent those character sequences inside a regular
1848expression character class, just quote the square brackets with the
1849backslash: "\[:" and ":\]".
1850
1851=item Ill-formed logical name |%s| in prime_env_iter
1852
1853(W) A warning peculiar to VMS. A logical name was encountered when preparing
1854to iterate over %ENV which violates the syntactic rules governing logical
1855names. Because it cannot be translated normally, it is skipped, and will not
1856appear in %ENV. This may be a benign occurrence, as some software packages
1857might directly modify logical name tables and introduce nonstandard names,
1858or it may indicate that a logical name table has been corrupted.
1859
1860=item regexp too big
1861
1862(F) The current implementation of regular expressions uses shorts as
1863address offsets within a string. Unfortunately this means that if
1864the regular expression compiles to longer than 32767, it'll blow up.
1865Usually when you want a regular expression this big, there is a better
1866way to do it with multiple statements. See L<perlre>.
1867
1868=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
1869
1870(D) Perl versions before 5.004 misinterpreted any type marker followed
1871by "$" and a digit. For example, "$$0" was incorrectly taken to mean
1872"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
1873
1874However, the developers of Perl 5.004 could not fix this bug completely,
1875because at least two widely-used modules depend on the old meaning of
1876"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
1877old (broken) way inside strings; but it generates this message as a
1878warning. And in Perl 5.005, this special treatment will cease.
1879
1880=back
3175b8cd 1881
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1882=head1 BUGS
1883
437784d6 1884If you find what you think is a bug, you might check the
14218588 1885articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
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1886There may also be information at http://www.perl.com/perl/, the Perl
1887Home Page.
1888
1889If you believe you have an unreported bug, please run the B<perlbug>
14218588 1890program included with your release. Make sure to trim your bug down
ba8251e8 1891to a tiny but sufficient test case. Your bug report, along with the
14218588 1892output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
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1893analysed by the Perl porting team.
1894
1895=head1 SEE ALSO
1896
1897The F<Changes> file for exhaustive details on what changed.
1898
1899The F<INSTALL> file for how to build Perl.
1900
1901The F<README> file for general stuff.
1902
1903The F<Artistic> and F<Copying> files for copyright information.
1904
1905=head1 HISTORY
1906
a5222a85
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1907Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
1908contributions from The Perl Porters.
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1909
1910Send omissions or corrections to <F<perlbug@perl.com>>.
1911
1912=cut