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1=head1 NAME
2
063663a9 3perldelta - what's new for perl v5.6.0
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4
5=head1 DESCRIPTION
6
7This document describes differences between the 5.005 release and this one.
8
7a95317d 9=head1 Core Enhancements
ba8251e8 10
7a95317d 11=head2 Interpreter cloning, threads, and concurrency
e02fdbd2 12
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13Perl 5.005_63 introduces the beginnings of support for running multiple
14interpreters concurrently in different threads. In conjunction with
15the perl_clone() API call, which can be used to selectively duplicate
16the state of any given interpreter, it is possible to compile a
17piece of code once in an interpreter, clone that interpreter
18one or more times, and run all the resulting interpreters in distinct
19threads.
a5222a85 20
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21On the Windows platform, this feature is used to emulate fork() at the
22interpreter level. See L<perlfork> for details about that.
e02fdbd2 23
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24This feature is still in evolution. It is eventually meant to be used
25to selectively clone a subroutine and data reachable from that
26subroutine in a separate interpreter and run the cloned subroutine
27in a separate thread. Since there is no shared data between the
28interpreters, little or no locking will be needed (unless parts of
29the symbol table are explicitly shared). This is obviously intended
30to be an easy-to-use replacement for the existing threads support.
757edf6f 31
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32Support for cloning interpreters and interpreter concurrency can be
33enabled using the -Dusethreads Configure option (see win32/Makefile for
34how to enable it on Windows.) The resulting perl executable will be
35functionally identical to one that was built with -Dmultiplicity, but
36the perl_clone() API call will only be available in the former.
4f25aa18 37
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38-Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
39enables Perl source code changes that provide a clear separation between
40the op tree and the data it operates with. The former is immutable, and
41can therefore be shared between an interpreter and all of its clones,
42while the latter is considered local to each interpreter, and is therefore
43copied for each clone.
4f25aa18 44
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45Note that building Perl with the -Dusemultiplicity Configure option
46is adequate if you wish to run multiple B<independent> interpreters
47concurrently in different threads. -Dusethreads only provides the
48additional functionality of the perl_clone() API call and other
49support for running B<cloned> interpreters concurrently.
08cd8952 50
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51 NOTE: This is an experimental feature. Implementation details are
52 subject to change.
08cd8952 53
7a95317d 54=head2 Lexically scoped warning categories
08cd8952 55
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56You can now control the granularity of warnings emitted by perl at a finer
57level using the C<use warnings> pragma. L<warnings> and L<perllexwarn>
58have copious documentation on this feature.
08cd8952 59
7a95317d 60=head2 Unicode and UTF-8 support
08cd8952 61
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62Perl now uses UTF-8 as its internal representation for character
63strings. The C<utf8> and C<bytes> pragmas are used to control this support
64in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
65more information.
08cd8952 66
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67This feature is expected to evolve quickly to support some form of I/O
68disciplines that can be used to specify the kind of input and output data
69(bytes or characters). Until that happens, additional modules from CPAN
70will be needed to complete the toolkit for dealing with Unicode.
08cd8952 71
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72 NOTE: This should be considered an experimental feature. Implementation
73 details are subject to change.
74
75=head2 Support for interpolating named characters
76
77The new C<\N> escape interpolates named characters within strings.
78For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
79with a unicode smiley face at the end.
80
81=head2 "our" declarations
82
83An "our" declaration introduces a value that can be best understood
84as a lexically scoped symbolic alias to a global variable in the
85package that was current where the variable was declared. This is
86mostly useful as an alternative to the C<vars> pragma, but also provides
87the opportunity to introduce typing and other attributes for such
88variables. See L<perlfunc/our>.
89
90=head2 Support for strings represented as a vector of ordinals
91
92Literals of the form C<v1.2.3.4> are now parsed as a string composed
93of characters with the specified ordinals. This is an alternative, more
94readable way to construct (possibly unicode) strings instead of
95interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
96C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
97parsed the same as C<v1.2.3>.
98
99Strings written in this form are also useful to represent version "numbers".
100It is easy to compare such version "numbers" (which are really just plain
101strings) using any of the usual string comparison operators C<eq>, C<ne>,
102C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
103C<&>, etc.
104
105In conjunction with the new C<$^V> magic variable (which contains
106the perl version as a string), such literals can be used as a readable way
107to check if you're running a particular version of Perl:
108
109 # this will parse in older versions of Perl also
110 if ($^V and $^V gt v5.6.0) {
111 # new features supported
112 }
113
114C<require> and C<use> also have some special magic to support such literals.
115They will be interpreted as a version rather than as a module name:
116
117 require v5.6.0; # croak if $^V lt v5.6.0
118 use v5.6.0; # same, but croaks at compile-time
119
120Alternatively, the C<v> may be omitted if there is more than one dot:
121
122 require 5.6.0;
123 use 5.6.0;
124
125Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
126to print ordinals of characters in arbitrary strings:
127
128 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
129 printf "%*vX", ":", $addr; # formats IPv6 address
130 printf "%*vb", " ", $bits; # displays bitstring
131
132See L<perldata/"Scalar value constructors"> for additional information.
08cd8952 133
7a95317d 134=head2 Improved Perl version numbering system
44dcb63b 135
063663a9 136Beginning with Perl version 5.6.0, the version number convention has been
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137changed to a "dotted integer" scheme that is more commonly found in open
138source projects.
139
140Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
063663a9 141The next development series following v5.6.0 will be numbered v5.7.x,
44dcb63b 142beginning with v5.7.0, and the next major production release following
063663a9 143v5.6.0 will be v5.8.0.
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144
145The English module now sets $PERL_VERSION to $^V (a string value) rather
146than C<$]> (a numeric value). (This is a potential incompatibility.
147Send us a report via perlbug if you are affected by this.)
148
149The v1.2.3 syntax is also now legal in Perl.
150See L<Support for strings represented as a vector of ordinals> for more on that.
151
152To cope with the new versioning system's use of at least three significant
153digits for each version component, the method used for incrementing the
154subversion number has also changed slightly. We assume that versions older
063663a9 155than v5.6.0 have been incrementing the subversion component in multiples of
44dcb63b 15610. Versions after v5.6.0 will increment them by 1. Thus, using the new
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157notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
158version following v5.6.0 will be v5.6.1 (which should be read as being
159equivalent to a floating point value of 5.006_001 in the older format,
160stored in C<$]>).
44dcb63b 161
7a95317d 162=head2 New syntax for declaring subroutine attributes
dd629d5b 163
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164Formerly, if you wanted to mark a subroutine as being a method call or
165as requiring an automatic lock() when it is entered, you had to declare
166that with a C<use attrs> pragma in the body of the subroutine.
167That can now be accomplished with declaration syntax, like this:
dd629d5b 168
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169 sub mymethod : locked method ;
170 ...
171 sub mymethod : locked method {
172 ...
173 }
dd629d5b 174
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175 sub othermethod :locked :method ;
176 ...
177 sub othermethod :locked :method {
178 ...
179 }
dd629d5b 180
757edf6f 181
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182(Note how only the first C<:> is mandatory, and whitespace surrounding
183the C<:> is optional.)
757edf6f 184
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185F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
186with the stubs they provide. See L<attributes>.
a5222a85 187
7a95317d 188=head2 File and directory handles can be autovivified
a5222a85 189
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190Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
191handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
192socket(), and accept()) now autovivify a file or directory handle
193if the handle passed to them is an uninitialized scalar variable. This
194allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
195to be used to create filehandles that will conveniently be closed
196automatically when the scope ends, provided there are no other references
197to them. This largely eliminates the need for typeglobs when opening
198filehandles that must be passed around, as in the following example:
a5222a85 199
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200 sub myopen {
201 open my $fh, "@_"
202 or die "Can't open '@_': $!";
203 return $fh;
204 }
a5222a85 205
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206 {
207 my $f = myopen("</etc/motd");
208 print <$f>;
209 # $f implicitly closed here
210 }
a5222a85 211
7a95317d 212=head2 open() with more than two arguments
a5222a85 213
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214If open() is passed three arguments instead of two, the second argument
215is used as the mode and the third argument is taken to be the file name.
216This is primarily useful for protecting against unintended magic behavior
217of the traditional two-argument form. See L<perlfunc/open>.
a5222a85 218
7a95317d 219=head2 64-bit support
a5222a85 220
7a95317d 221Any platform that has 64-bit integers either
a5222a85 222
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223 (1) natively as longs or ints
224 (2) via special compiler flags
225 (3) using long long or int64_t
a5222a85 226
7a95317d 227is able to use "quads" (64-bit integers) as follows:
a5222a85 228
7a95317d 229=over 4
a5222a85 230
7a95317d 231=item *
a5222a85 232
7a95317d 233constants (decimal, hexadecimal, octal, binary) in the code
a5222a85 234
7a95317d 235=item *
a5222a85 236
7a95317d 237arguments to oct() and hex()
a5222a85 238
7a95317d 239=item *
a5222a85 240
7a95317d 241arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
a5222a85 242
7a95317d 243=item *
39429b3b 244
7a95317d 245printed as such
39429b3b 246
7a95317d 247=item *
39429b3b 248
7a95317d 249pack() and unpack() "q" and "Q" formats
39429b3b 250
7a95317d 251=item *
39429b3b 252
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253in basic arithmetics: + - * / % (NOTE: operating close to the limits
254of the integer values may produce surprising results)
39429b3b 255
7a95317d 256=item *
39429b3b 257
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258in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
259to be 32 bits wide but now operate on the full native width.)
39429b3b 260
7a95317d 261=item *
39429b3b 262
7a95317d 263vec()
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264
265=back
266
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267Note that unless you have the case (a) you will have to configure
268and compile Perl using the -Duse64bitint Configure flag.
67d3893f 269
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270 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
271 deprecated. Use -Duse64bitint instead.
67d3893f 272
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273There are actually two modes of 64-bitness: the first one is achieved
274using Configure -Duse64bitint and the second one using Configure
275-Duse64bitall. The difference is that the first one is minimal and
276the second one maximal. The first works in more places than the second.
67d3893f 277
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278The C<use64bitint> does only as much as is required to get 64-bit
279integers into Perl (this may mean, for example, using "long longs")
280while your memory may still be limited to 2 gigabytes (because your
281pointers could still be 32-bit). Note that the name C<64bitint> does
282not imply that your C compiler will be using 64-bit C<int>s (it might,
283but it doesn't have to): the C<use64bitint> means that you will be
284able to have 64 bits wide scalar values.
67d3893f 285
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286The C<use64bitall> goes all the way by attempting to switch also
287integers (if it can), longs (and pointers) to being 64-bit. This may
288create an even more binary incompatible Perl than -Duse64bitint: the
289resulting executable may not run at all in a 32-bit box, or you may
290have to reboot/reconfigure/rebuild your operating system to be 64-bit
291aware.
67d3893f 292
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293Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
294nor -Duse64bitall.
67d3893f 295
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296Last but not least: note that due to Perl's habit of always using
297floating point numbers, the quads are still not true integers.
298When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
299-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
300are silently promoted to floating point numbers, after which they will
301start losing precision (in their lower digits).
67d3893f 302
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303 NOTE: 64-bit support is still experimental on most platforms.
304 Existing support only covers the LP64 data model. In particular, the
305 LLP64 data model is not yet supported. 64-bit libraries and system
306 APIs on many platforms have not stabilized--your mileage may vary.
642f9deb 307
7a95317d 308=head2 Large file support
a5222a85 309
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310If you have filesystems that support "large files" (files larger than
3112 gigabytes), you may now also be able to create and access them from
312Perl.
a5222a85 313
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314 NOTE: The default action is to enable large file support, if
315 available on the platform.
a5222a85 316
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317If the large file support is on, and you have a Fcntl constant
318O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
319of sysopen().
a5222a85 320
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321Beware that unless your filesystem also supports "sparse files" seeking
322to umpteen petabytes may be inadvisable.
642f9deb 323
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324Note that in addition to requiring a proper file system to do large
325files you may also need to adjust your per-process (or your
326per-system, or per-process-group, or per-user-group) maximum filesize
327limits before running Perl scripts that try to handle large files,
328especially if you intend to write such files.
a5222a85 329
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330Finally, in addition to your process/process group maximum filesize
331limits, you may have quota limits on your filesystems that stop you
332(your user id or your user group id) from using large files.
a5222a85 333
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334Adjusting your process/user/group/file system/operating system limits
335is outside the scope of Perl core language. For process limits, you
336may try increasing the limits using your shell's limits/limit/ulimit
337command before running Perl. The BSD::Resource extension (not
338included with the standard Perl distribution) may also be of use, it
339offers the getrlimit/setrlimit interface that can be used to adjust
340process resource usage limits, including the maximum filesize limit.
a5222a85 341
7a95317d 342=head2 Long doubles
67d3893f 343
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344In some systems you may be able to use long doubles to enhance the
345range and precision of your double precision floating point numbers
346(that is, Perl's numbers). Use Configure -Duselongdouble to enable
347this support (if it is available).
49c10eea 348
7a95317d 349=head2 "more bits"
67d3893f 350
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351You can "Configure -Dusemorebits" to turn on both the 64-bit support
352and the long double support.
ba8251e8 353
7a95317d 354=head2 Enhanced support for sort() subroutines
9d73390d 355
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356Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
357now be used as sort subroutines. In either case, the two elements to
358be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
21bad921 359
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360For unprototyped sort subroutines, the historical behavior of passing
361the elements to be compared as the global variables $a and $b remains
362unchanged.
9d73390d 363
7a95317d 364=head2 C<sort $coderef @foo> allowed
af365420 365
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366sort() did not accept a subroutine reference as the comparison
367function in earlier versions. This is now permitted.
af365420 368
7a95317d 369=head2 File globbing implemented internally
af365420 370
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371Perl now uses the File::Glob implementation of the glob() operator
372automatically. This avoids using an external csh process and the
373problems associated with it.
af365420 374
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375 NOTE: This is currently an experimental feature. Interfaces and
376 implementation are subject to change.
af365420 377
7a95317d 378=item Support for CHECK blocks
af365420 379
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380In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
381subroutines named C<CHECK> are now special. These are queued up during
382compilation and behave similar to END blocks, except they are called at
383the end of compilation rather than at the end of execution. They cannot
384be called directly.
af365420 385
7a95317d 386=head2 POSIX character class syntax [: :] supported
af365420 387
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388For example to match alphabetic characters use /[[:alpha:]]/.
389See L<perlre> for details.
9d73390d 390
7a95317d 391=item Better pseudo-random number generator
9d73390d 392
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393In 5.005_0x and earlier, perl's rand() function used the C library
394rand(3) function. As of 5.005_52, Configure tests for drand48(),
395random(), and rand() (in that order) and picks the first one it finds.
a5222a85 396
7a95317d 397These changes should result in better random numbers from rand().
a5222a85 398
7a95317d 399=head2 Improved C<qw//> operator
a5222a85 400
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401The C<qw//> operator is now evaluated at compile time into a true list
402instead of being replaced with a run time call to C<split()>. This
403removes the confusing misbehaviour of C<qw//> in scalar context, which
404had inherited that behaviour from split().
a5222a85 405
7a95317d 406Thus:
16070b82 407
7a95317d 408 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
16070b82 409
7a95317d 410now correctly prints "3|a", instead of "2|a".
16070b82 411
7a95317d 412=item Better worst-case behavior of hashes
16070b82 413
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414Small changes in the hashing algorithm have been implemented in
415order to improve the distribution of lower order bits in the
416hashed value. This is expected to yield better performance on
417keys that are repeated sequences.
16070b82 418
7a95317d 419=head2 pack() format 'Z' supported
16070b82 420
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421The new format type 'Z' is useful for packing and unpacking null-terminated
422strings. See L<perlfunc/"pack">.
16070b82 423
7a95317d 424=head2 pack() format modifier '!' supported
a5222a85 425
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426The new format type modifier '!' is useful for packing and unpacking
427native shorts, ints, and longs. See L<perlfunc/"pack">.
dd629d5b 428
7a95317d 429=head2 pack() and unpack() support counted strings
dd629d5b 430
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431The template character '/' can be used to specify a counted string
432type to be packed or unpacked. See L<perlfunc/"pack">.
1761cee5 433
7a95317d 434=head2 Comments in pack() templates
1761cee5 435
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436The '#' character in a template introduces a comment up to
437end of the line. This facilitates documentation of pack()
438templates.
44dcb63b 439
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440=head2 Weak references
441
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442In previous versions of Perl, you couldn't cache objects so as
443to allow them to be deleted if the last reference from outside
444the cache is deleted. The reference in the cache would hold a
445reference count on the object and the objects would never be
446destroyed.
447
448Another familiar problem is with circular references. When an
449object references itself, its reference count would never go
450down to zero, and it would not get destroyed until the program
451is about to exit.
452
453Weak references solve this by allowing you to "weaken" any
454reference, that is, make it not count towards the reference count.
455When the last non-weak reference to an object is deleted, the object
456is destroyed and all the weak references to the object are
457automatically undef-ed.
a5222a85 458
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459To use this feature, you need the WeakRef package from CPAN, which
460contains additional documentation.
461
7a95317d 462 NOTE: This is an experimental feature. Details are subject to change.
becf2bd3 463
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464=head2 Binary numbers supported
465
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466Binary numbers are now supported as literals, in s?printf formats, and
467C<oct()>:
468
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469 $answer = 0b101010;
470 printf "The answer is: %b\n", oct("0b101010");
4f19785b 471
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472=head2 Lvalue subroutines
473
474Subroutines can now return modifiable lvalues.
475See L<perlsub/"Lvalue subroutines">.
476
477 NOTE: This is an experimental feature. Details are subject to change.
478
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479=head2 Some arrows may be omitted in calls through references
480
481Perl now allows the arrow to be omitted in many constructs
482involving subroutine calls through references. For example,
c47ff5f1 483C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
a5222a85 484This is rather similar to how the arrow may be omitted from
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485C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
486required for C<< foo(10)->('bar') >>.
a5222a85 487
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488=head2 Boolean assignment operators are legal lvalues
489
490Constructs such as C<($a ||= 2) += 1> are now allowed.
491
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492=head2 exists() is supported on subroutine names
493
494The exists() builtin now works on subroutine names. A subroutine
495is considered to exist if it has been declared (even if implicitly).
496See L<perlfunc/exists> for examples.
497
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498=head2 exists() and delete() are supported on array elements
499
500The exists() and delete() builtins now work on simple arrays as well.
501The behavior is similar to that on hash elements.
502
8ea97a1e 503exists() can be used to check whether an array element has been
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504initialized. This avoids autovivifying array elements that don't exist.
505If the array is tied, the EXISTS() method in the corresponding tied
506package will be invoked.
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507
508delete() may be used to remove an element from the array and return
4375e838 509it. The array element at that position returns to its uninitialized
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510state, so that testing for the same element with exists() will return
511false. If the element happens to be the one at the end, the size of
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512the array also shrinks up to the highest element that tests true for
513exists(), or 0 if none such is found. If the array is tied, the DELETE()
514method in the corresponding tied package will be invoked.
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515
516See L<perlfunc/exists> and L<perlfunc/delete> for examples.
517
7a95317d 518=head2 Pseudo-hashes work better
9c107f78 519
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520Dereferencing some types of reference values in a pseudo-hash,
521such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
522been corrected.
4bca7e4f 523
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524When applied to a pseudo-hash element, exists() now reports whether
525the specified value exists, not merely if the key is valid.
9c107f78 526
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527delete() now works on pseudo-hashes. When given a pseudo-hash element
528or slice it deletes the values corresponding to the keys (but not the keys
529themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
a5222a85 530
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531Pseudo-hash slices with constant keys are now optimized to array lookups
532at compile-time.
a5222a85 533
7a95317d 534List assignments to pseudo-hash slices are now supported.
9c107f78 535
7a95317d
GS
536The C<fields> pragma now provides ways to create pseudo-hashes, via
537fields::new() and fields::phash(). See L<fields>.
9c107f78 538
7a95317d
GS
539 NOTE: The pseudo-hash data type continues to be experimental.
540 Limiting oneself to the interface elements provided by the
541 fields pragma will provide protection from any future changes.
a5222a85 542
7a95317d 543=head2 Automatic flushing of output buffers
a5222a85 544
7a95317d
GS
545fork(), exec(), system(), qx//, and pipe open()s now flush buffers
546of all files opened for output when the operation was attempted. This
547mostly eliminates confusing buffering mishaps suffered by users unaware
548of how Perl internally handles I/O.
9c107f78 549
7a95317d
GS
550This is not supported on some platforms like Solaris where a suitably
551correct implementation of fflush(NULL) isn't available.
9c107f78 552
7a95317d 553=head2 Better diagnostics on meaningless filehandle operations
a5222a85 554
7a95317d
GS
555Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
556are compile time errors. Attempting to read from filehandles that
557were opened only for writing will now produce warnings (just as
558writing to read-only filehandles does).
a5222a85 559
7a95317d 560=head2 Where possible, buffered data discarded from duped input filehandle
a5222a85 561
7a95317d
GS
562C<< open(NEW, "<&OLD") >> now attempts to discard any data that
563was previously read and buffered in C<OLD> before duping the handle.
564On platforms where doing this is allowed, the next read operation
565on C<NEW> will return the same data as the corresponding operation
566on C<OLD>. Formerly, it would have returned the data from the start
567of the following disk block instead.
a5222a85 568
7a95317d 569=head2 eof() has the same old magic as <>
1fad5d67 570
7a95317d
GS
571C<eof()> would return true if no attempt to read from C<< <> >> had
572yet been made. C<eof()> has been changed to have a little magic of its
573own, it now opens the C<< <> >> files.
972b05a9 574
7a95317d 575=head2 binmode() can be used to set :crlf and :raw modes
972b05a9 576
7a95317d
GS
577binmode() now accepts a second argument that specifies a discipline
578for the handle in question. The two pseudo-disciplines ":raw" and
579":crlf" are currently supported on DOS-derivative platforms.
580See L<perlfunc/"binmode"> and L<open>.
9c107f78 581
7a95317d 582=head2 C<-T> filetest recognizes UTF-8 encoded files as "text"
9c107f78 583
7a95317d
GS
584The algorithm used for the C<-T> filetest has been enhanced to
585correctly identify UTF-8 content as "text".
9c107f78 586
7a95317d 587=head2 system(), backticks and pipe open now reflect exec() failure
55f6b6ec 588
7a95317d
GS
589On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
590etc., are implemented via fork() and exec(). When the underlying
591exec() fails, earlier versions did not report the error properly,
592since the exec() happened to be in a different process.
55f6b6ec 593
7a95317d
GS
594The child process now communicates with the parent about the
595error in launching the external command, which allows these
596constructs to return with their usual error value and set $!.
49c10eea 597
7a95317d 598=head2 Improved diagnostics
49c10eea 599
7a95317d
GS
600Line numbers are no longer suppressed (under most likely circumstances)
601during the global destruction phase.
2d4389e4 602
7a95317d
GS
603Diagnostics emitted from code running in threads other than the main
604thread are now accompanied by the thread ID.
2d4389e4 605
7a95317d
GS
606Embedded null characters in diagnostics now actually show up. They
607used to truncate the message in prior versions.
55f6b6ec 608
7a95317d
GS
609$foo::a and $foo::b are now exempt from "possible typo" warnings only
610if sort() is encountered in package C<foo>.
55f6b6ec 611
7a95317d
GS
612Unrecognized alphabetic escapes encountered when parsing quote
613constructs now generate a warning, since they may take on new
614semantics in later versions of Perl.
2d4389e4 615
7a95317d
GS
616Many diagnostics now report the internal operation in which the warning
617was provoked, like so:
eed7fde4 618
7a95317d
GS
619 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
620 Use of uninitialized value in print at (eval 1) line 1.
eed7fde4 621
7a95317d
GS
622Diagnostics that occur within eval may also report the file and line
623number where the eval is located, in addition to the eval sequence
624number and the line number within the evaluated text itself. For
625example:
475d79b5 626
7a95317d 627 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
aa855319 628
7a95317d 629=head2 Diagnostics follow STDERR
aa855319 630
7a95317d
GS
631Diagnostic output now goes to whichever file the C<STDERR> handle
632is pointing at, instead of always going to the underlying C runtime
633library's C<stderr>.
aa855319 634
7a95317d 635=item More consistent close-on-exec behavior
09bef843 636
7a95317d
GS
637On systems that support a close-on-exec flag on filehandles, the
638flag is now set for any handles created by pipe(), socketpair(),
639socket(), and accept(), if that is warranted by the value of $^F
640that may be in effect. Earlier versions neglected to set the flag
641for handles created with these operators. See L<perlfunc/pipe>,
642L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
643and L<perlvar/$^F>.
43481408 644
7a95317d 645=head2 syswrite() ease-of-use
43481408 646
7a95317d 647The length argument of C<syswrite()> has become optional.
43481408 648
62c18ce2
GS
649=head2 Better syntax checks on parenthesized unary operators
650
651Expressions such as:
652
14218588
GS
653 print defined(&foo,&bar,&baz);
654 print uc("foo","bar","baz");
655 undef($foo,&bar);
62c18ce2 656
7711098a 657used to be accidentally allowed in earlier versions, and produced
14218588
GS
658unpredictable behaviour. Some produced ancillary warnings
659when used in this way; others silently did the wrong thing.
62c18ce2
GS
660
661The parenthesized forms of most unary operators that expect a single
14218588
GS
662argument now ensure that they are not called with more than one
663argument, making the cases shown above syntax errors. The usual
664behaviour of:
62c18ce2 665
14218588
GS
666 print defined &foo, &bar, &baz;
667 print uc "foo", "bar", "baz";
668 undef $foo, &bar;
62c18ce2
GS
669
670remains unchanged. See L<perlop>.
671
7a95317d 672=head2 Bit operators support full native integer width
26ef7447 673
7a95317d
GS
674The bit operators (& | ^ ~ << >>) now operate on the full native
675integral width (the exact size of which is available in $Config{ivsize}).
676For example, if your platform is either natively 64-bit or if Perl
677has been configured to use 64-bit integers, these operations apply
678to 8 bytes (as opposed to 4 bytes on 32-bit platforms).
679For portability, be sure to mask off the excess bits in the result of
680unary C<~>, e.g., C<~$x & 0xffffffff>.
26ef7447 681
7a95317d 682=head2 Improved security features
8127e0e3 683
7a95317d
GS
684More potentially unsafe operations taint their results for improved
685security.
5a929a98 686
7a95317d
GS
687The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(),
688and getpwuid() are now tainted, because the user can affect their own
689encrypted password and login shell.
5a929a98 690
7a95317d
GS
691The variable modified by shmread(), and messages returned by msgrcv()
692(and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
693because other untrusted processes can modify messages and shared memory
694segments for their own nefarious purposes.
ee3907e2 695
7a95317d 696=item More functional bareword prototype (*)
ee3907e2 697
7a95317d
GS
698Bareword prototypes have been rationalized to enable them to be used
699to override builtins that accept barewords and interpret them in
700a special way, such as C<require> or C<do>.
f29c64d6 701
7a95317d
GS
702Arguments prototyped as C<*> will now be visible within the subroutine
703as either a simple scalar or as a reference to a typeglob.
704See L<perlsub/Prototypes>.
f29c64d6 705
7a95317d 706=head2 C<require> and C<do> may be overridden
a5222a85 707
7a95317d
GS
708C<require> and C<do 'file'> operations may be overridden locally
709by importing subroutines of the same name into the current package
710(or globally by importing them into the CORE::GLOBAL:: namespace).
711Overriding C<require> will also affect C<use>, provided the override
712is visible at compile-time.
713See L<perlsub/"Overriding Built-in Functions">.
a5222a85 714
2b92dfce
GS
715=head2 $^X variables may now have names longer than one character
716
717Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
718error. Now variable names that begin with a control character may be
719arbitrarily long. However, for compatibility reasons, these variables
720I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 721C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
2b92dfce
GS
722than one control character, such as C<${^XY^Z}>, are illegal.
723
14218588
GS
724The old syntax has not changed. As before, `^X' may be either a
725literal control-X character or the two-character sequence `caret' plus
726`X'. When braces are omitted, the variable name stops after the
2b92dfce 727control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 728C<$^X . "YZ"> as before.
2b92dfce
GS
729
730As before, lexical variables may not have names beginning with control
731characters. As before, variables whose names begin with a control
14218588
GS
732character are always forced to be in package `main'. All such variables
733are reserved for future extensions, except those that begin with
09bef843 734C<^_>, which may be used by user programs and are guaranteed not to
14218588 735acquire special meaning in any future version of Perl.
2b92dfce 736
a5222a85
GS
737=head2 New variable $^C reflects C<-c> switch
738
08cd8952 739C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
740in compile-only mode (i.e. via the C<-c> switch). Since
741BEGIN blocks are executed under such conditions, this variable
742enables perl code to determine whether actions that make sense
743only during normal running are warranted. See L<perlvar>.
744
063663a9 745=head2 New variable $^V contains Perl version as a string
16070b82 746
da2094fd 747C<$^V> contains the Perl version number as a string composed of
642f9deb 748characters whose ordinals match the version numbers, i.e. v5.6.0.
063663a9 749This may be used in string comparisons.
44dcb63b
GS
750
751See C<Support for strings represented as a vector of ordinals> for an
752example.
16070b82 753
a5222a85
GS
754=head2 Optional Y2K warnings
755
756If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
757it emits optional warnings when concatenating the number 19
758with another number.
759
760This behavior must be specifically enabled when running Configure.
b4bc034f 761See F<INSTALL> and F<README.Y2K>.
a5222a85 762
7a95317d 763=head1 Modules and Pragmata
fbad3eb5 764
7a95317d 765=head2 Modules
0244c3a4 766
7a95317d 767=over 4
0244c3a4 768
7a95317d 769=item attributes
0244c3a4 770
7a95317d
GS
771While used internally by Perl as a pragma, this module also
772provides a way to fetch subroutine and variable attributes.
773See L<attributes>.
0244c3a4 774
7a95317d 775=item B
a5222a85 776
7a95317d
GS
777The Perl Compiler suite has been extensively reworked for this
778release. More of the standard Perl testsuite passes when run
779under the Compiler, but there is still a significant way to
780go to achieve production quality compiled executables.
a5222a85 781
7a95317d 782 NOTE: The Compiler suite remains highly experimental. The
4375e838 783 generated code may not be correct, even when it manages to execute
7a95317d 784 without errors.
a5222a85 785
7a95317d 786=item Benchmark
45bc9206 787
7a95317d
GS
788Overall, Benchmark results exhibit lower average error and better timing
789accuracy.
45bc9206 790
7a95317d
GS
791You can now run tests for I<n> seconds instead of guessing the right
792number of tests to run: e.g., timethese(-5, ...) will run each
793code for at least 5 CPU seconds. Zero as the "number of repetitions"
794means "for at least 3 CPU seconds". The output format has also
795changed. For example:
023ceb80 796
7a95317d 797 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
af8c498a 798
7a95317d 799will now output something like this:
af8c498a 800
7a95317d
GS
801 Benchmark: running a, b, each for at least 5 CPU seconds...
802 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
803 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
a5222a85 804
7a95317d
GS
805New features: "each for at least N CPU seconds...", "wallclock secs",
806and the "@ operations/CPU second (n=operations)".
a5222a85 807
7a95317d
GS
808timethese() now returns a reference to a hash of Benchmark objects containing
809the test results, keyed on the names of the tests.
820475bd 810
7a95317d
GS
811timethis() now returns the iterations field in the Benchmark result object
812instead of 0.
820475bd 813
7a95317d
GS
814timethese(), timethis(), and the new cmpthese() (see below) can also take
815a format specifier of 'none' to suppress output.
a5222a85 816
7a95317d
GS
817A new function countit() is just like timeit() except that it takes a
818TIME instead of a COUNT.
a5222a85 819
7a95317d
GS
820A new function cmpthese() prints a chart comparing the results of each test
821returned from a timethese() call. For each possible pair of tests, the
822percentage speed difference (iters/sec or seconds/iter) is shown.
a5222a85 823
7a95317d 824For other details, see L<Benchmark>.
a5222a85 825
7a95317d 826=item ByteLoader
a5222a85 827
7a95317d
GS
828The ByteLoader is a dedicated extension to generate and run
829Perl bytecode. See L<ByteLoader>.
a5222a85 830
7a95317d 831=item constant
a5222a85 832
7a95317d 833References can now be used.
a5222a85 834
7a95317d
GS
835The new version also allows a leading underscore in constant names, but
836disallows a double leading underscore (as in "__LINE__"). Some other names
837are disallowed or warned against, including BEGIN, END, etc. Some names
838which were forced into main:: used to fail silently in some cases; now they're
839fatal (outside of main::) and an optional warning (inside of main::).
840The ability to detect whether a constant had been set with a given name has
841been added.
4bca7e4f 842
7a95317d 843See L<constant>.
a5222a85 844
7a95317d 845=item charnames
a5222a85 846
7a95317d 847This pragma implements the C<\N> string escape. See L<charnames>.
01020589 848
7a95317d 849=item Data::Dumper
479ba383 850
7a95317d
GS
851A C<Maxdepth> setting can be specified to avoid venturing
852too deeply into deep data structures. See L<Data::Dumper>.
479ba383 853
7a95317d
GS
854The XSUB implementation of Dump() is now automatically called if the
855C<Useqq> setting is not in use.
a5222a85 856
7a95317d 857Dumping C<qr//> objects works correctly.
a5222a85 858
7a95317d 859=item DB
a5222a85 860
7a95317d
GS
861C<DB> is an experimental module that exposes a clean abstraction
862to Perl's debugging API.
a5222a85 863
7a95317d 864=item DB_File
a5222a85 865
7a95317d
GS
866DB_File can now be built with Berkeley DB versions 1, 2 or 3.
867See C<ext/DB_File/Changes>.
a5222a85 868
7a95317d 869=item Devel::DProf
a5222a85 870
7a95317d
GS
871Devel::DProf, a Perl source code profiler has been added. See
872L<Devel::DProf> and L<dprofpp>.
a5222a85 873
7a95317d 874=item Devel::Peek
a5222a85 875
7a95317d
GS
876The Devel::Peek module provides access to the internal representation
877of Perl variables and data. It is a data debugging tool for the XS programmer.
a5222a85 878
7a95317d 879=item Dumpvalue
54195c32 880
7a95317d 881The Dumpvalue module provides screen dumps of Perl data.
67d3893f 882
7a95317d 883=item DynaLoader
54195c32 884
7a95317d
GS
885DynaLoader now supports a dl_unload_file() function on platforms that
886support unloading shared objects using dlclose().
a5222a85 887
7a95317d
GS
888Perl can also optionally arrange to unload all extension shared objects
889loaded by Perl. To enable this, build Perl with the Configure option
890C<-Accflags=-DDL_UNLOAD_ALL_AT_EXIT>. (This maybe useful if you are
891using Apache with mod_perl.)
a5222a85 892
7a95317d 893=item English
a5222a85 894
7a95317d
GS
895$PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
896(a numeric value).
a5222a85 897
7a95317d 898=item Env
a5222a85 899
7a95317d
GS
900Env now supports accessing environment variables like PATH as array
901variables.
a5222a85 902
7a95317d 903=item Fcntl
a5222a85 904
7a95317d
GS
905More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
906large file (more than 4GB) access (NOTE: the O_LARGEFILE is
907automatically added to sysopen() flags if large file support has been
908configured, as is the default), Free/Net/OpenBSD locking behaviour
909flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
910mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
911constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
912C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
913are available via the C<:mode> tag.
a5222a85 914
7a95317d 915=item File::Compare
a5222a85 916
7a95317d
GS
917A compare_text() function has been added, which allows custom
918comparison functions. See L<File::Compare>.
a5222a85 919
7a95317d 920=item File::Find
a5222a85 921
7a95317d
GS
922File::Find now works correctly when the wanted() function is either
923autoloaded or is a symbolic reference.
a5222a85 924
7a95317d
GS
925A bug that caused File::Find to lose track of the working directory
926when pruning top-level directories has been fixed.
a5222a85 927
7a95317d
GS
928File::Find now also supports several other options to control its
929behavior. It can follow symbolic links if the C<follow> option is
930specified. Enabling the C<no_chdir> option will make File::Find skip
931changing the current directory when walking directories. The C<untaint>
932flag can be useful when running with taint checks enabled.
a5222a85 933
7a95317d 934See L<File::Find>.
a5222a85 935
7a95317d 936=item File::Glob
a5222a85 937
7a95317d
GS
938This extension implements BSD-style file globbing. By default,
939it will also be used for the internal implementation of the glob()
940operator. See L<File::Glob>.
a5222a85 941
7a95317d 942=item File::Spec
a5222a85 943
7a95317d
GS
944New methods have been added to the File::Spec module: devnull() returns
945the name of the null device (/dev/null on Unix) and tmpdir() the name of
946the temp directory (normally /tmp on Unix). There are now also methods
947to convert between absolute and relative filenames: abs2rel() and
948rel2abs(). For compatibility with operating systems that specify volume
949names in file paths, the splitpath(), splitdir(), and catdir() methods
950have been added.
a5222a85 951
7a95317d 952=item File::Spec::Functions
a5222a85 953
7a95317d
GS
954The new File::Spec::Functions modules provides a function interface
955to the File::Spec module. Allows shorthand
a5222a85 956
7a95317d 957 $fullname = catfile($dir1, $dir2, $file);
a5222a85 958
7a95317d 959instead of
a398b1cd 960
7a95317d 961 $fullname = File::Spec->catfile($dir1, $dir2, $file);
a398b1cd 962
7a95317d 963=item Getopt::Long
a398b1cd 964
7a95317d
GS
965Getopt::Long licensing has changed to allow the Perl Artistic License
966as well as the GPL. It used to be GPL only, which got in the way of
967non-GPL applications that wanted to use Getopt::Long.
a398b1cd 968
7a95317d
GS
969Getopt::Long encourages the use of Pod::Usage to produce help
970messages. For example:
a5222a85 971
7a95317d
GS
972 use Getopt::Long;
973 use Pod::Usage;
974 my $man = 0;
975 my $help = 0;
976 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
977 pod2usage(1) if $help;
978 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
979
980 __END__
a5222a85 981
7a95317d 982 =head1 NAME
a5222a85 983
7a95317d 984 sample - Using GetOpt::Long and Pod::Usage
a5222a85 985
7a95317d 986 =head1 SYNOPSIS
a5222a85 987
7a95317d 988 sample [options] [file ...]
a5222a85 989
7a95317d
GS
990 Options:
991 -help brief help message
992 -man full documentation
a5222a85 993
7a95317d 994 =head1 OPTIONS
a5222a85 995
7a95317d 996 =over 8
ba8251e8 997
7a95317d 998 =item B<-help>
5fdc711f 999
7a95317d 1000 Print a brief help message and exits.
5fdc711f 1001
7a95317d 1002 =item B<-man>
6c67e1bb 1003
7a95317d 1004 Prints the manual page and exits.
5fdc711f 1005
7a95317d 1006 =back
ee3907e2 1007
7a95317d 1008 =head1 DESCRIPTION
ee3907e2 1009
4375e838 1010 B<This program> will read the given input file(s) and do something
7a95317d 1011 useful with the contents thereof.
6c67e1bb 1012
7a95317d 1013 =cut
5fdc711f 1014
7a95317d 1015See L<Pod::Usage> for details.
6c67e1bb 1016
7a95317d
GS
1017A bug that prevented the non-option call-back <> from being
1018specified as the first argument has been fixed.
00ad96e1 1019
7a95317d
GS
1020To specify the characters < and > as option starters, use ><. Note,
1021however, that changing option starters is strongly deprecated.
00ad96e1 1022
7a95317d 1023=item IO
27806c82 1024
7a95317d
GS
1025write() and syswrite() will now accept a single-argument
1026form of the call, for consistency with Perl's syswrite().
27806c82 1027
7a95317d
GS
1028You can now create a TCP-based IO::Socket::INET without forcing
1029a connect attempt. This allows you to configure its options
1030(like making it non-blocking) and then call connect() manually.
5fdc711f 1031
7a95317d
GS
1032A bug that prevented the IO::Socket::protocol() accessor
1033from ever returning the correct value has been corrected.
a5222a85 1034
7a95317d
GS
1035IO::Socket::connect now uses non-blocking IO instead of alarm()
1036to do connect timeouts.
d524f05e 1037
7a95317d
GS
1038IO::Socket::accept now uses select() instead of alarm() for doing
1039timeouts.
d524f05e 1040
7a95317d 1041IO::Socket::INET->new now sets $! correctly on failure. $@ is
4375e838 1042still set for backwards compatibility.
d524f05e 1043
7a95317d 1044=item JPL
d524f05e 1045
7a95317d
GS
1046Java Perl Lingo is now distributed with Perl. See jpl/README
1047for more information.
d524f05e 1048
7a95317d 1049=item lib
d524f05e 1050
7a95317d
GS
1051C<use lib> now weeds out any trailing duplicate entries.
1052C<no lib> removes all named entries.
d524f05e 1053
7a95317d 1054=item Math::BigInt
d524f05e 1055
7a95317d
GS
1056The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1057and C<~> are now supported on bigints.
d524f05e 1058
7a95317d 1059=item Math::Complex
a5222a85 1060
7a95317d
GS
1061The accessor methods Re, Im, arg, abs, rho, and theta can now also
1062act as mutators (accessor $z->Re(), mutator $z->Re(3)).
063663a9 1063
7a95317d
GS
1064The class method C<display_format> and the corresponding object method
1065C<display_format>, in addition to accepting just one argument, now can
1066also accept a parameter hash. Recognized keys of a parameter hash are
1067C<"style">, which corresponds to the old one parameter case, and two
1068new parameters: C<"format">, which is a printf()-style format string
1069(defaults usually to C<"%.15g">, you can revert to the default by
1070setting the format string to C<undef>) used for both parts of a
1071complex number, and C<"polar_pretty_print"> (defaults to true),
1072which controls whether an attempt is made to try to recognize small
1073multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1074polar complex number.
063663a9 1075
7a95317d
GS
1076The potentially disruptive change is that in list context both methods
1077now I<return the parameter hash>, instead of only the value of the
1078C<"style"> parameter.
063663a9 1079
7a95317d 1080=item Math::Trig
a5222a85 1081
7a95317d
GS
1082A little bit of radial trigonometry (cylindrical and spherical),
1083radial coordinate conversions, and the great circle distance were added.
c93fa817 1084
7a95317d 1085=item Pod::Parser, Pod::InputObjects
c93fa817 1086
7a95317d
GS
1087Pod::Parser is a base class for parsing and selecting sections of
1088pod documentation from an input stream. This module takes care of
1089identifying pod paragraphs and commands in the input and hands off the
1090parsed paragraphs and commands to user-defined methods which are free
1091to interpret or translate them as they see fit.
c93fa817 1092
7a95317d
GS
1093Pod::InputObjects defines some input objects needed by Pod::Parser, and
1094for advanced users of Pod::Parser that need more about a command besides
1095its name and text.
c93fa817 1096
7a95317d
GS
1097As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
1098"base parser code" recommended for use by all pod2xxx translators.
1099Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1100to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1101underway. For any questions or comments about pod parsing and translating
1102issues and utilities, please use the pod-people@perl.org mailing list.
c93fa817 1103
7a95317d 1104For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
c93fa817 1105
7a95317d 1106=item Pod::Checker, podchecker
c93fa817 1107
7a95317d
GS
1108This utility checks pod files for correct syntax, according to
1109L<perlpod>. Obvious errors are flagged as such, while warnings are
1110printed for mistakes that can be handled gracefully. The checklist is
1111not complete yet. See L<Pod::Checker>.
c93fa817 1112
7a95317d 1113=item Pod::ParseUtils, Pod::Find
c93fa817 1114
7a95317d
GS
1115These modules provide a set of gizmos that are useful mainly for pod
1116translators. L<Pod::Find|Pod::Find> traverses directory structures and
1117returns found pod files, along with their canonical names (like
1118C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1119B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1120(for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1121(for caching information about pod files, e.g., link nodes).
a5222a85 1122
7a95317d 1123=item Pod::Select, podselect
a5222a85 1124
7a95317d
GS
1125Pod::Select is a subclass of Pod::Parser which provides a function
1126named "podselect()" to filter out user-specified sections of raw pod
1127documentation from an input stream. podselect is a script that provides
1128access to Pod::Select from other scripts to be used as a filter.
1129See L<Pod::Select>.
a5222a85 1130
7a95317d 1131=item Pod::Usage, pod2usage
a5222a85 1132
7a95317d
GS
1133Pod::Usage provides the function "pod2usage()" to print usage messages for
1134a Perl script based on its embedded pod documentation. The pod2usage()
1135function is generally useful to all script authors since it lets them
1136write and maintain a single source (the pods) for documentation, thus
1137removing the need to create and maintain redundant usage message text
1138consisting of information already in the pods.
a5222a85 1139
7a95317d
GS
1140There is also a pod2usage script which can be used from other kinds of
1141scripts to print usage messages from pods (even for non-Perl scripts
1142with pods embedded in comments).
a5222a85 1143
7a95317d 1144For details and examples, please see L<Pod::Usage>.
a5222a85 1145
7a95317d 1146=item Pod::Text and Pod::Man
a5222a85 1147
7a95317d
GS
1148Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1149still available for backwards compatibility, the module now has a new
1150preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1151module is easily subclassed for tweaks to the output, and two such
1152subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1153using termcap information, and Pod::Text::Color for markup with ANSI color
1154sequences) are now standard.
a5222a85 1155
7a95317d
GS
1156pod2man has been turned into a module, Pod::Man, which also uses
1157Pod::Parser. In the process, several outstanding bugs related to quotes
1158in section headers, quoting of code escapes, and nested lists have been
1159fixed. pod2man is now a wrapper script around this module.
42b8b86c 1160
7a95317d 1161=item SDBM_File
a5222a85 1162
7a95317d
GS
1163An EXISTS method has been added to this module (and sdbm_exists() has
1164been added to the underlying sdbm library), so one can now call exists
1165on an SDBM_File tied hash and get the correct result, rather than a
1166runtime error.
883d36a6 1167
7a95317d
GS
1168A bug that may have caused data loss when more than one disk block
1169happens to be read from the database in a single FETCH() has been
1170fixed.
c39cd008 1171
7a95317d 1172=item Sys::Syslog
16070b82 1173
7a95317d
GS
1174Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1175no longer requires syslog.ph to exist.
6c67e1bb 1176
7a95317d 1177=item Sys::Hostname
6c67e1bb 1178
7a95317d
GS
1179Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1180uname() if they exist.
09bef843 1181
7a95317d 1182=item Term::ANSIColor
09bef843 1183
7a95317d
GS
1184Term::ANSIColor is a very simple module to provide easy and readable
1185access to the ANSI color and highlighting escape sequences, supported by
1186most ANSI terminal emulators. It is now included standard.
2675e62c 1187
7a95317d 1188=item Time::Local
2675e62c 1189
7a95317d
GS
1190The timelocal() and timegm() functions used to silently return bogus
1191results when the date fell outside the machine's integer range. They
1192now consistently croak() if the date falls in an unsupported range.
2675e62c 1193
7a95317d 1194=item Win32
2675e62c 1195
7a95317d
GS
1196The error return value in list context has been changed for all functions
1197that return a list of values. Previously these functions returned a list
1198with a single element C<undef> if an error occurred. Now these functions
1199return the empty list in these situations. This applies to the following
1200functions:
6c67e1bb 1201
7a95317d
GS
1202 Win32::FsType
1203 Win32::GetOSVersion
14218588 1204
7a95317d
GS
1205The remaining functions are unchanged and continue to return C<undef> on
1206error even in list context.
6c67e1bb 1207
7a95317d
GS
1208The Win32::SetLastError(ERROR) function has been added as a complement
1209to the Win32::GetLastError() function.
6c67e1bb 1210
7a95317d
GS
1211The new Win32::GetFullPathName(FILENAME) returns the full absolute
1212pathname for FILENAME in scalar context. In list context it returns
1213a two-element list containing the fully qualified directory name and
1214the filename. See L<Win32>.
6c67e1bb 1215
7a95317d 1216=item XSLoader
6c67e1bb 1217
7a95317d
GS
1218The XSLoader extension is a simpler alternative to DynaLoader.
1219See L<XSLoader>.
6c67e1bb 1220
7a95317d 1221=item DBM Filters
6c67e1bb 1222
7a95317d
GS
1223A new feature called "DBM Filters" has been added to all the
1224DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1225DBM Filters add four new methods to each DBM module:
6c67e1bb 1226
7a95317d
GS
1227 filter_store_key
1228 filter_store_value
1229 filter_fetch_key
1230 filter_fetch_value
6c67e1bb 1231
7a95317d
GS
1232These can be used to filter key-value pairs before the pairs are
1233written to the database or just after they are read from the database.
1234See L<perldbmfilter> for further information.
09bef843 1235
7a95317d 1236=back
09bef843 1237
7a95317d 1238=head2 Pragmata
6c67e1bb 1239
7a95317d
GS
1240C<use attrs> is now obsolete, and is only provided for
1241backward-compatibility. It's been replaced by the C<sub : attributes>
1242syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
6c67e1bb 1243
7a95317d
GS
1244Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1245See L<perllexwarn>.
6c67e1bb 1246
7a95317d
GS
1247C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1248...). Currently only one subpragma implemented, "use filetest
1249'access';", that uses access(2) or equivalent to check permissions
1250instead of using stat(2) as usual. This matters in filesystems
1251where there are ACLs (access control lists): the stat(2) might lie,
1252but access(2) knows better.
6c67e1bb 1253
7a95317d
GS
1254The C<open> pragma can be used to specify default disciplines for
1255handle constructors (e.g. open()) and for qx//. The two
1256pseudo-disciplines C<:raw> and C<:crlf> are currently supported on
1257DOS-derivative platforms (i.e. where binmode is not a no-op).
1258See also L</"binmode() can be used to set :crlf and :raw modes">.
afebc493 1259
7a95317d 1260=head1 Utility Changes
afebc493 1261
7a95317d 1262=head2 dprofpp
e02fdbd2 1263
7a95317d
GS
1264C<dprofpp> is used to display profile data generated using C<Devel::DProf>.
1265See L<dprofpp>.
ba8251e8 1266
7a95317d 1267=head2 find2perl
3e8c4fa0 1268
7a95317d
GS
1269The C<find2perl> utility now uses the enhanced features of the File::Find
1270module. The -depth and -follow options are supported. Pod documentation
1271is also included in the script.
b7d8191e 1272
7a95317d 1273=head2 h2xs
09bef843 1274
7a95317d
GS
1275The C<h2xs> tool can now work in conjunction with C<C::Scan> (available
1276from CPAN) to automatically parse real-life header files. The C<-M>,
1277C<-a>, C<-k>, and C<-o> options are new.
09bef843 1278
7a95317d 1279=head2 perlcc
a5222a85 1280
7a95317d
GS
1281C<perlcc> now supports the C and Bytecode backends. By default,
1282it generates output from the simple C backend rather than the
1283optimized C backend.
501fbaef 1284
7a95317d 1285Support for non-Unix platforms has been improved.
a5222a85 1286
7a95317d 1287=head2 perldoc
f29c64d6 1288
7a95317d
GS
1289C<perldoc> has been reworked to avoid possible security holes.
1290It will not by default let itself be run as the superuser, but you
1291may still use the B<-U> switch to try to make it drop privileges
1292first.
f29c64d6 1293
7a95317d 1294=head2 The Perl Debugger
a5222a85 1295
7a95317d
GS
1296Many bug fixes and enhancements were added to F<perl5db.pl>, the
1297Perl debugger. The help documentation was rearranged. New commands
1298include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1299actions, C<man I<docpage>> to run your doc viewer on some perl
1300docset, and support for quoted options. The help information was
1301rearranged, and should be viewable once again if you're using B<less>
1302as your pager. A serious security hole was plugged--you should
1303immediately remove all older versions of the Perl debugger as
1304installed in previous releases, all the way back to perl3, from
1305your system to avoid being bitten by this.
83763826 1306
7a95317d 1307=head1 Improved Documentation
83763826 1308
7a95317d
GS
1309Many of the platform-specific README files are now part of the perl
1310installation. See L<perl> for the complete list.
a5222a85 1311
7a95317d 1312=over 4
a5222a85 1313
7a95317d 1314=item perlapi.pod
a5222a85 1315
7a95317d 1316The official list of public Perl API functions.
a5222a85 1317
7a95317d 1318=item perlboot.pod
a5222a85 1319
7a95317d 1320A tutorial for beginners on object-oriented Perl.
0f1923bd 1321
7a95317d 1322=item perlcompile.pod
a5222a85 1323
7a95317d 1324An introduction to using the Perl Compiler suite.
a5222a85 1325
7a95317d 1326=item perldbmfilter.pod
a5222a85 1327
7a95317d 1328A howto document on using the DBM filter facility.
a5222a85 1329
7a95317d 1330=item perldebug.pod
a5222a85 1331
7a95317d
GS
1332All material unrelated to running the Perl debugger, plus all
1333low-level guts-like details that risked crushing the casual user
1334of the debugger, have been relocated from the old manpage to the
1335next entry below.
f29c64d6 1336
7a95317d 1337=item perldebguts.pod
f29c64d6 1338
7a95317d
GS
1339This new manpage contains excessively low-level material not related
1340to the Perl debugger, but slightly related to debugging Perl itself.
1341It also contains some arcane internal details of how the debugging
1342process works that may only be of interest to developers of Perl
1343debuggers.
b7d8191e 1344
7a95317d 1345=item perlfork.pod
b7d8191e 1346
7a95317d 1347Notes on the fork() emulation currently available for the Windows platform.
23d2500b 1348
7a95317d 1349=item perlfilter.pod
23d2500b 1350
7a95317d 1351An introduction to writing Perl source filters.
23d2500b 1352
7a95317d 1353=item perlhack.pod
b7d8191e 1354
7a95317d 1355Some guidelines for hacking the Perl source code.
54e82ce5 1356
7a95317d 1357=item perlintern.pod
155776c0 1358
7a95317d
GS
1359A list of internal functions in the Perl source code.
1360(List is currently empty.)
155776c0 1361
7a95317d 1362=item perllexwarn.pod
155776c0 1363
7a95317d
GS
1364Introduction and reference information about lexically scoped
1365warning categories.
155776c0 1366
7a95317d 1367=item perlnumber.pod
b7d8191e 1368
7a95317d 1369Detailed information about numbers as they are represented in Perl.
54e82ce5 1370
7a95317d 1371=item perlopentut.pod
54e82ce5 1372
7a95317d 1373A tutorial on using open() effectively.
54e82ce5 1374
7a95317d 1375=item perlreftut.pod
54e82ce5 1376
7a95317d 1377A tutorial that introduces the essentials of references.
54e82ce5 1378
7a95317d 1379=item perltootc.pod
a5222a85 1380
7a95317d 1381A tutorial on managing class data for object modules.
f505c983 1382
7a95317d 1383=item perltodo.pod
f505c983 1384
7a95317d
GS
1385Discussion of the most often wanted features that may someday be
1386supported in Perl.
44dcb63b 1387
7a95317d 1388=item perlunicode.pod
44dcb63b 1389
7a95317d 1390An introduction to Unicode support features in Perl.
2675e62c 1391
7a95317d 1392=back
2675e62c 1393
7a95317d 1394=head1 Performance enhancements
b7d8191e 1395
7a95317d 1396=head2 Simple sort() using { $a <=> $b } and the like are optimized
b7d8191e 1397
7a95317d
GS
1398Many common sort() operations using a simple inlined block are now
1399optimized for faster performance.
a5222a85 1400
7a95317d 1401=head2 Optimized assignments to lexical variables
a5222a85 1402
7a95317d
GS
1403Certain operations in the RHS of assignment statements have been
1404optimized to directly set the lexical variable on the LHS,
1405eliminating redundant copying overheads.
a5222a85 1406
7a95317d 1407=head2 Faster subroutine calls
a5222a85 1408
7a95317d
GS
1409Minor changes in how subroutine calls are handled internally
1410provide marginal improvements in performance.
a5222a85 1411
7a95317d 1412=item delete(), each(), values() and hash iteration are faster
81793b90 1413
7a95317d
GS
1414The hash values returned by delete(), each(), values() and hashes in a
1415list context are the actual values in the hash, instead of copies.
1416This results in significantly better performance, because it eliminates
1417needless copying in most situations.
81793b90 1418
7a95317d 1419=head1 Installation and Configuration Improvements
becf2bd3 1420
7a95317d 1421=head2 -Dusethreads means something different
becf2bd3 1422
7a95317d
GS
1423The -Dusethreads flag now enables the experimental interpreter-based thread
1424support by default. To get the flavor of experimental threads that was in
14255.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
f505c983 1426
7a95317d
GS
1427As of v5.6.0, interpreter-threads support is still lacking a way to
1428create new threads from Perl (i.e., C<use Thread;> will not work with
1429interpreter threads). C<use Thread;> continues to be available when you
1430specify the -Duse5005threads option to Configure, bugs and all.
f505c983 1431
7a95317d
GS
1432 NOTE: Support for threads continues to be an experimental feature.
1433 Interfaces and implementation are subject to sudden and drastic changes.
f505c983 1434
7a95317d 1435=head2 New Configure flags
f505c983 1436
7a95317d
GS
1437The following new flags may be enabled on the Configure command line
1438by running Configure with C<-Dflag>.
f505c983 1439
7a95317d
GS
1440 usemultiplicity
1441 usethreads useithreads (new interpreter threads: no Perl API yet)
1442 usethreads use5005threads (threads as they were in 5.005)
f505c983 1443
7a95317d
GS
1444 use64bitint (equal to now deprecated 'use64bits')
1445 use64bitall
f505c983 1446
7a95317d
GS
1447 uselongdouble
1448 usemorebits
1449 uselargefiles
1450 usesocks (only SOCKS v5 supported)
a5222a85 1451
7a95317d 1452=head2 Threadedness and 64-bitness now more daring
c6edd1b7 1453
7a95317d
GS
1454The Configure options enabling the use of threads and the use of
145564-bitness are now more daring in the sense that they no more have an
1456explicit list of operating systems of known threads/64-bit
1457capabilities. In other words: if your operating system has the
1458necessary APIs and datatypes, you should be able just to go ahead and
1459use them, for threads by Configure -Dusethreads, and for 64 bits
1460either explicitly by Configure -Duse64bitint or implicitly if your
1461system has 64-bit wide datatypes. See also L<"64-bit support">.
c6edd1b7 1462
7a95317d 1463=head2 Long Doubles
c6edd1b7 1464
7a95317d
GS
1465Some platforms have "long doubles", floating point numbers of even
1466larger range than ordinary "doubles". To enable using long doubles for
1467Perl's scalars, use -Duselongdouble.
c6edd1b7 1468
7a95317d 1469=head2 -Dusemorebits
c6edd1b7 1470
7a95317d
GS
1471You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
1472See also L<"64-bit support">.
c6edd1b7 1473
7a95317d 1474=head2 -Duselargefiles
c6edd1b7 1475
7a95317d
GS
1476Some platforms support system APIs that are capable of handling large files
1477(typically, files larger than two gigabytes). Perl will try to use these
1478APIs if you ask for -Duselargefiles.
c6edd1b7 1479
7a95317d 1480See L<"Large file support"> for more information.
c6edd1b7 1481
7a95317d 1482=head2 installusrbinperl
c6edd1b7 1483
7a95317d
GS
1484You can use "Configure -Uinstallusrbinperl" which causes installperl
1485to skip installing perl also as /usr/bin/perl. This is useful if you
1486prefer not to modify /usr/bin for some reason or another but harmful
1487because many scripts assume to find Perl in /usr/bin/perl.
c6edd1b7 1488
7a95317d 1489=head2 SOCKS support
c6edd1b7 1490
7a95317d
GS
1491You can use "Configure -Dusesocks" which causes Perl to probe
1492for the SOCKS proxy protocol library (v5, not v4). For more information
1493on SOCKS, see:
c6edd1b7 1494
7a95317d 1495 http://www.socks.nec.com/
c6edd1b7 1496
7a95317d 1497=head2 C<-A> flag
c6edd1b7 1498
7a95317d
GS
1499You can "post-edit" the Configure variables using the Configure C<-A>
1500switch. The editing happens immediately after the platform specific
1501hints files have been processed but before the actual configuration
1502process starts. Run C<Configure -h> to find out the full C<-A> syntax.
c6edd1b7 1503
7a95317d 1504=head2 Enhanced Installation Directories
c6edd1b7 1505
7a95317d
GS
1506The installation structure has been enriched to improve the support
1507for maintaining multiple versions of perl, to provide locations for
1508vendor-supplied modules, scripts, and manpages, and to ease maintenance
1509of locally-added modules, scripts, and manpages. See the section on
1510Installation Directories in the INSTALL file for complete details.
1511For most users building and installing from source, the defaults should
1512be fine.
c6edd1b7 1513
7a95317d
GS
1514If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
1515special values for library directories, you might wish to consider using
1516the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
1517config.sh file from an earlier version of perl, you should be sure to
1518check that Configure makes sensible choices for the new directories.
1519See INSTALL for complete details.
c6edd1b7 1520
7a95317d 1521=head1 Platform specific changes
c6edd1b7 1522
7a95317d 1523=head2 Supported platforms
c6edd1b7 1524
7a95317d 1525=over 4
a5222a85 1526
7a95317d 1527=item *
a5222a85 1528
7a95317d
GS
1529The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1530extension.
36f31b50 1531
7a95317d 1532=item *
36f31b50 1533
7a95317d 1534GNU/Hurd is now supported.
a5222a85 1535
7a95317d 1536=item *
a5222a85 1537
7a95317d 1538Rhapsody/Darwin is now supported.
883d36a6 1539
7a95317d 1540=item *
883d36a6 1541
106325ad 1542EPOC is now supported (on Psion 5).
e16b8f49 1543
7a95317d 1544=item *
e16b8f49 1545
7a95317d 1546The cygwin port (formerly cygwin32) has been greatly improved.
7711098a 1547
7a95317d 1548=back
b7d8191e 1549
7a95317d 1550=head2 DOS
16357284 1551
7a95317d 1552=over 4
16357284 1553
7a95317d 1554=item *
b7d8191e 1555
7a95317d 1556Perl now works with djgpp 2.02 (and 2.03 alpha).
b7d8191e 1557
7a95317d 1558=item *
d4629d6a 1559
7a95317d 1560Environment variable names are not converted to uppercase any more.
d4629d6a 1561
7a95317d 1562=item *
d4629d6a 1563
7a95317d 1564Incorrect exit codes from backticks have been fixed.
d4629d6a 1565
7a95317d 1566=item *
d4629d6a 1567
7a95317d 1568This port continues to use its own builtin globbing (not File::Glob).
d4629d6a 1569
7a95317d 1570=back
d4629d6a 1571
7a95317d 1572=head2 OS390 (OpenEdition MVS)
d4629d6a 1573
7a95317d
GS
1574Support for this EBCDIC platform has not been renewed in this release.
1575There are difficulties in reconciling Perl's standardization on UTF-8
1576as its internal representation for characters with the EBCDIC character
1577set, because the two are incompatible.
d4629d6a 1578
7a95317d
GS
1579It is unclear whether future versions will renew support for this
1580platform, but the possibility exists.
d4629d6a 1581
7a95317d 1582=head2 VMS
d4629d6a 1583
7a95317d 1584Numerous revisions and extensions to configuration, build, testing, and
4375e838 1585installation process to accommodate core changes and VMS-specific options.
d4629d6a 1586
7a95317d
GS
1587Expand %ENV-handling code to allow runtime mapping to logical names,
1588CLI symbols, and CRTL environ array.
d4629d6a 1589
7a95317d
GS
1590Extension of subprocess invocation code to accept filespecs as command
1591"verbs".
a5222a85 1592
7a95317d
GS
1593Add to Perl command line processing the ability to use default file types and
1594to recognize Unix-style C<2E<gt>&1>.
a5222a85 1595
7a95317d 1596Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
a5222a85 1597
7a95317d
GS
1598Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
1599
1600Barewords at start of Unix-syntax paths may be treated as text rather than
1601only as logical names.
1602
1603Optional secure translation of several logical names used internally by Perl.
1604
1605Miscellaneous bugfixing and porting of new core code to VMS.
e3e5e1ea 1606
7a95317d
GS
1607Thanks are gladly extended to the many people who have contributed VMS
1608patches, testing, and ideas.
a5222a85 1609
7a95317d 1610=head2 Win32
f4b9d880 1611
7a95317d
GS
1612Perl can now emulate fork() internally, using multiple interpreters running
1613in different concurrent threads. This support must be enabled at build
1614time. See L<perlfork> for detailed information.
f4b9d880 1615
7a95317d
GS
1616When given a pathname that consists only of a drivename, such as C<A:>,
1617opendir() and stat() now use the current working directory for the drive
1618rather than the drive root.
a5222a85 1619
7a95317d
GS
1620The builtin XSUB functions in the Win32:: namespace are documented. See
1621L<Win32>.
8ce86de8 1622
7a95317d 1623$^X now contains the full path name of the running executable.
8ce86de8 1624
7a95317d
GS
1625A Win32::GetLongPathName() function is provided to complement
1626Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
f91101c9 1627
7a95317d 1628POSIX::uname() is supported.
f91101c9 1629
7a95317d
GS
1630system(1,...) now returns true process IDs rather than process
1631handles. kill() accepts any real process id, rather than strictly
1632return values from system(1,...).
e3e5e1ea 1633
7a95317d
GS
1634For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1635test whether a process exists.
e3e5e1ea 1636
7a95317d 1637The C<Shell> module is supported.
06ef4121 1638
7a95317d
GS
1639Better support for building Perl under command.com in Windows 95
1640has been added.
06ef4121 1641
7a95317d
GS
1642Scripts are read in binary mode by default to allow ByteLoader (and
1643the filter mechanism in general) to work properly. For compatibility,
1644the DATA filehandle will be set to text mode if a carriage return is
1645detected at the end of the line containing the __END__ or __DATA__
1646token; if not, the DATA filehandle will be left open in binary mode.
1647Earlier versions always opened the DATA filehandle in text mode.
8fe0a5c4 1648
7a95317d
GS
1649The glob() operator is implemented via the C<File::Glob> extension,
1650which supports glob syntax of the C shell. This increases the flexibility
1651of the glob() operator, but there may be compatibility issues for
1652programs that relied on the older globbing syntax. If you want to
1653preserve compatibility with the older syntax, you might want to run
1654perl with C<-MFile::DosGlob>. For details and compatibility information,
1655see L<File::Glob>.
8fe0a5c4 1656
7a95317d 1657=head1 Significant bug fixes
8fe0a5c4 1658
7a95317d 1659=head2 <HANDLE> on empty files
8fe0a5c4 1660
7a95317d
GS
1661With C<$/> set to C<undef>, "slurping" an empty file returns a string of
1662zero length (instead of C<undef>, as it used to) the first time the
1663HANDLE is read after C<$/> is set to C<undef>. Further reads yield
1664C<undef>.
8fe0a5c4 1665
7a95317d
GS
1666This means that the following will append "foo" to an empty file (it used
1667to do nothing):
8fe0a5c4 1668
7a95317d 1669 perl -0777 -pi -e 's/^/foo/' empty_file
23d2500b 1670
7a95317d 1671The behaviour of:
23d2500b 1672
7a95317d 1673 perl -pi -e 's/^/foo/' empty_file
9fe6733a 1674
7a95317d 1675is unchanged (it continues to leave the file empty).
9fe6733a 1676
7a95317d 1677=head2 C<eval '...'> improvements
9fe6733a 1678
7a95317d
GS
1679Line numbers (as reflected by caller() and most diagnostics) within
1680C<eval '...'> were often incorrect where here documents were involved.
1681This has been corrected.
9fe6733a 1682
7a95317d
GS
1683Lexical lookups for variables appearing in C<eval '...'> within
1684functions that were themselves called within an C<eval '...'> were
1685searching the wrong place for lexicals. The lexical search now
1686correctly ends at the subroutine's block boundary.
3e8c4fa0 1687
7a95317d
GS
1688The use of C<return> within C<eval {...}> caused $@ not to be reset
1689correctly when no exception occurred within the eval. This has
1690been fixed.
3e8c4fa0 1691
7a95317d
GS
1692Parsing of here documents used to be flawed when they appeared as
1693the replacement expression in C<eval 's/.../.../e'>. This has
1694been fixed.
09bef843 1695
7a95317d 1696=head2 All compilation errors are true errors
6c67e1bb 1697
4375e838 1698Some "errors" encountered at compile time were by necessity
7a95317d
GS
1699generated as warnings followed by eventual termination of the
1700program. This enabled more such errors to be reported in a
1701single run, rather than causing a hard stop at the first error
1702that was encountered.
6c67e1bb 1703
7a95317d
GS
1704The mechanism for reporting such errors has been reimplemented
1705to queue compile-time errors and report them at the end of the
1706compilation as true errors rather than as warnings. This fixes
1707cases where error messages leaked through in the form of warnings
1708when code was compiled at run time using C<eval STRING>, and
1709also allows such errors to be reliably trapped using C<eval "...">.
ba8251e8 1710
7a95317d 1711=head2 Implicitly closed filehandles are safer
a5222a85 1712
7a95317d
GS
1713Sometimes implicitly closed filehandles (as when they are localized,
1714and Perl automatically closes them on exiting the scope) could
1715inadvertently set $? or $!. This has been corrected.
a5222a85 1716
a5222a85 1717
7a95317d 1718=head2 Behavior of list slices is more consistent
055fd3a9 1719
7a95317d
GS
1720When taking a slice of a literal list (as opposed to a slice of
1721an array or hash), Perl used to return an empty list if the
1722result happened to be composed of all undef values.
055fd3a9 1723
7a95317d
GS
1724The new behavior is to produce an empty list if (and only if)
1725the original list was empty. Consider the following example:
055fd3a9 1726
7a95317d 1727 @a = (1,undef,undef,2)[2,1,2];
055fd3a9 1728
7a95317d
GS
1729The old behavior would have resulted in @a having no elements.
1730The new behavior ensures it has three undefined elements.
ba8251e8 1731
7a95317d
GS
1732Note in particular that the behavior of slices of the following
1733cases remains unchanged:
5fdc711f 1734
7a95317d
GS
1735 @a = ()[1,2];
1736 @a = (getpwent)[7,0];
1737 @a = (anything_returning_empty_list())[2,1,2];
1738 @a = @b[2,1,2];
1739 @a = @c{'a','b','c'};
954c1994 1740
7a95317d 1741See L<perldata>.
954c1994 1742
7a95317d 1743=head2 C<(\$)> prototype and C<$foo{a}>
883d36a6 1744
7a95317d
GS
1745A scalar reference prototype now correctly allows a hash or
1746array element in that slot.
883d36a6 1747
7a95317d 1748=head2 C<goto &sub> and AUTOLOAD
055fd3a9 1749
7a95317d
GS
1750The C<goto &sub> construct works correctly when C<&sub> happens
1751to be autoloaded.
055fd3a9 1752
7a95317d 1753=head2 C<-bareword> allowed under C<use integer>
055fd3a9 1754
7a95317d
GS
1755The autoquoting of barewords preceded by C<-> did not work
1756in prior versions when the C<integer> pragma was enabled.
1757This has been fixed.
055fd3a9 1758
7a95317d 1759=head2 Failures in DESTROY()
c7c04614 1760
7a95317d
GS
1761When code in a destructor threw an exception, it went unnoticed
1762in earlier versions of Perl, unless someone happened to be
1763looking in $@ just after the point the destructor happened to
1764run. Such failures are now visible as warnings when warnings are
1765enabled.
c7c04614 1766
7a95317d 1767=head2 Locale bugs fixed
883d36a6 1768
7a95317d
GS
1769printf() and sprintf() previously reset the numeric locale
1770back to the default "C" locale. This has been fixed.
883d36a6 1771
7a95317d
GS
1772Numbers formatted according to the local numeric locale
1773(such as using a decimal comma instead of a decimal dot) caused
1774"isn't numeric" warnings, even while the operations accessing
1775those numbers produced correct results. These warnings have been
1776discontinued.
954c1994 1777
7a95317d 1778=head2 Memory leaks
954c1994 1779
7a95317d
GS
1780The C<eval 'return sub {...}'> construct could sometimes leak
1781memory. This has been fixed.
f8284313 1782
7a95317d
GS
1783Operations that aren't filehandle constructors used to leak memory
1784when used on invalid filehandles. This has been fixed.
5fdc711f 1785
7a95317d
GS
1786Constructs that modified C<@_> could fail to deallocate values
1787in C<@_> and thus leak memory. This has been corrected.
5fdc711f 1788
7a95317d 1789=head2 Spurious subroutine stubs after failed subroutine calls
5fdc711f 1790
7a95317d
GS
1791Perl could sometimes create empty subroutine stubs when a
1792subroutine was not found in the package. Such cases stopped
1793later method lookups from progressing into base packages.
1794This has been corrected.
694468e3 1795
7a95317d 1796=head2 Taint failures under C<-U>
694468e3 1797
7a95317d
GS
1798When running in unsafe mode, taint violations could sometimes
1799cause silent failures. This has been fixed.
1800
1801=head2 END blocks and the C<-c> switch
1802
1803Prior versions used to run BEGIN B<and> END blocks when Perl was
1804run in compile-only mode. Since this is typically not the expected
1805behavior, END blocks are not executed anymore when the C<-c> switch
1806is used.
14218588 1807
7a95317d 1808See L<CHECK blocks> for how to run things when the compile phase ends.
14218588 1809
7a95317d 1810=head2 Potential to leak DATA filehandles
393fec97 1811
7a95317d
GS
1812Using the C<__DATA__> token creates an implicit filehandle to
1813the file that contains the token. It is the program's
1814responsibility to close it when it is done reading from it.
393fec97 1815
7a95317d
GS
1816This caveat is now better explained in the documentation.
1817See L<perldata>.
e02fdbd2 1818
73b437c8 1819=head1 New or Changed Diagnostics
ba8251e8 1820
a99ba403
GS
1821=over 4
1822
56e90b21
GS
1823=item "%s" variable %s masks earlier declaration in same %s
1824
ddda08b7 1825(W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
56e90b21
GS
1826effectively eliminating all access to the previous instance. This is almost
1827always a typographical error. Note that the earlier variable will still exist
1828until the end of the scope or until all closure referents to it are
1829destroyed.
1830
33633739
GS
1831=item "my sub" not yet implemented
1832
1833(F) Lexically scoped subroutines are not yet implemented. Don't try that
1834yet.
1835
1836=item "our" variable %s redeclared
1837
ddda08b7 1838(W misc) You seem to have already declared the same global once before in the
33633739
GS
1839current lexical scope.
1840
a99ba403
GS
1841=item '!' allowed only after types %s
1842
1843(F) The '!' is allowed in pack() and unpack() only after certain types.
1844See L<perlfunc/pack>.
1845
1846=item / cannot take a count
1847
1848(F) You had an unpack template indicating a counted-length string,
1849but you have also specified an explicit size for the string.
1850See L<perlfunc/pack>.
1851
1852=item / must be followed by a, A or Z
1853
1854(F) You had an unpack template indicating a counted-length string,
1855which must be followed by one of the letters a, A or Z
1856to indicate what sort of string is to be unpacked.
1857See L<perlfunc/pack>.
1858
1859=item / must be followed by a*, A* or Z*
1860
437784d6 1861(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1862Currently the only things that can have their length counted are a*, A* or Z*.
1863See L<perlfunc/pack>.
1864
1865=item / must follow a numeric type
1866
1867(F) You had an unpack template that contained a '#',
1868but this did not follow some numeric unpack specification.
1869See L<perlfunc/pack>.
1870
a99ba403
GS
1871=item /%s/: Unrecognized escape \\%c passed through
1872
ddda08b7 1873(W regexp) You used a backslash-character combination which is not recognized
a99ba403 1874by Perl. This combination appears in an interpolated variable or a
1028017a
JH
1875C<'>-delimited regular expression. The character was understood literally.
1876
1877=item /%s/: Unrecognized escape \\%c in character class passed through
1878
ddda08b7 1879(W regexp) You used a backslash-character combination which is not recognized
1028017a 1880by Perl inside character classes. The character was understood literally.
a99ba403
GS
1881
1882=item /%s/ should probably be written as "%s"
1883
ddda08b7 1884(W syntax) You have used a pattern where Perl expected to find a string,
437784d6 1885as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
1886or false result of matching the pattern against $_ as the string,
1887which is probably not what you had in mind.
1888
1889=item %s() called too early to check prototype
1890
ddda08b7 1891(W prototype) You've called a function that has a prototype before the parser saw a
a99ba403
GS
1892definition or declaration for it, and Perl could not check that the call
1893conforms to the prototype. You need to either add an early prototype
1894declaration for the subroutine in question, or move the subroutine
1895definition ahead of the call to get proper prototype checking. Alternatively,
1896if you are certain that you're calling the function correctly, you may put
1897an ampersand before the name to avoid the warning. See L<perlsub>.
1898
56e90b21
GS
1899=item %s argument is not a HASH or ARRAY element
1900
1901(F) The argument to exists() must be a hash or array element, such as:
1902
1903 $foo{$bar}
7a95317d 1904 $ref->{"susie"}[12]
56e90b21
GS
1905
1906=item %s argument is not a HASH or ARRAY element or slice
1907
1908(F) The argument to delete() must be either a hash or array element, such as:
1909
1910 $foo{$bar}
7a95317d 1911 $ref->{"susie"}[12]
56e90b21
GS
1912
1913or a hash or array slice, such as:
1914
1915 @foo[$bar, $baz, $xyzzy]
1916 @{$ref->[12]}{"susie", "queue"}
1917
afebc493
GS
1918=item %s argument is not a subroutine name
1919
1920(F) The argument to exists() for C<exists &sub> must be a subroutine
1921name, and not a subroutine call. C<exists &sub()> will generate this error.
1922
09bef843
SB
1923=item %s package attribute may clash with future reserved word: %s
1924
ddda08b7 1925(W reserved) A lowercase attribute name was used that had a package-specific handler.
09bef843
SB
1926That name might have a meaning to Perl itself some day, even though it
1927doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1928See L<attributes>.
1929
cc507455 1930=item (in cleanup) %s
6b121555 1931
ddda08b7 1932(W misc) This prefix usually indicates that a DESTROY() method raised
a99ba403
GS
1933the indicated exception. Since destructors are usually called by
1934the system at arbitrary points during execution, and often a vast
1935number of times, the warning is issued only once for any number
1936of failures that would otherwise result in the same message being
1937repeated.
1938
1939Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1940could also result in this warning. See L<perlcall/G_KEEPERR>.
1941
1942=item <> should be quotes
1943
c47ff5f1 1944(F) You wrote C<< require <file> >> when you should have written
a99ba403
GS
1945C<require 'file'>.
1946
1947=item Attempt to join self
1948
1949(F) You tried to join a thread from within itself, which is an
1950impossible task. You may be joining the wrong thread, or you may
1951need to move the join() to some other thread.
1952
1953=item Bad evalled substitution pattern
1954
1955(F) You've used the /e switch to evaluate the replacement for a
1956substitution, but perl found a syntax error in the code to evaluate,
1957most likely an unexpected right brace '}'.
1958
1959=item Bad realloc() ignored
1960
1961(S) An internal routine called realloc() on something that had never been
1962malloc()ed in the first place. Mandatory, but can be disabled by
1963setting environment variable C<PERL_BADFREE> to 1.
1964
34d09196
GS
1965=item Bareword found in conditional
1966
ddda08b7 1967(W bareword) The compiler found a bareword where it expected a conditional,
34d09196
GS
1968which often indicates that an || or && was parsed as part of the
1969last argument of the previous construct, for example:
1970
1971 open FOO || die;
1972
1973It may also indicate a misspelled constant that has been interpreted
1974as a bareword:
1975
1976 use constant TYPO => 1;
1977 if (TYOP) { print "foo" }
1978
1979The C<strict> pragma is useful in avoiding such errors.
1980
a99ba403
GS
1981=item Binary number > 0b11111111111111111111111111111111 non-portable
1982
ddda08b7 1983(W portable) The binary number you specified is larger than 2**32-1
a99ba403
GS
1984(4294967295) and therefore non-portable between systems. See
1985L<perlport> for more on portability concerns.
1986
1987=item Bit vector size > 32 non-portable
1988
ddda08b7 1989(W portable) Using bit vector sizes larger than 32 is non-portable.
a99ba403
GS
1990
1991=item Buffer overflow in prime_env_iter: %s
1992
ddda08b7 1993(W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
a99ba403
GS
1994%ENV, it encountered a logical name or symbol definition which was too long,
1995so it was truncated to the string shown.
1996
1997=item Can't check filesystem of script "%s"
1998
1999(P) For some reason you can't check the filesystem of the script for nosuid.
2000
56e90b21
GS
2001=item Can't declare class for non-scalar %s in "%s"
2002
2003(S) Currently, only scalar variables can declared with a specific class
2004qualifier in a "my" or "our" declaration. The semantics may be extended
2005for other types of variables in future.
2006
2007=item Can't declare %s in "%s"
2008
2009(F) Only scalar, array, and hash variables may be declared as "my" or
2010"our" variables. They must have ordinary identifiers as names.
2011
0b5b802d
GS
2012=item Can't ignore signal CHLD, forcing to default
2013
ddda08b7 2014(W signal) Perl has detected that it is being run with the SIGCHLD signal
0b5b802d
GS
2015(sometimes known as SIGCLD) disabled. Since disabling this signal
2016will interfere with proper determination of exit status of child
2017processes, Perl has reset the signal to its default value.
2018This situation typically indicates that the parent program under
642f9deb 2019which Perl may be running (e.g., cron) is being very careless.
0b5b802d 2020
a99ba403
GS
2021=item Can't modify non-lvalue subroutine call
2022
437784d6
GS
2023(F) Subroutines meant to be used in lvalue context should be declared as
2024such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
2025
2026=item Can't read CRTL environ
2027
2028(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2029from the CRTL's internal environment array and discovered the array was
2030missing. You need to figure out where your CRTL misplaced its environ
2031or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2032
2033=item Can't remove %s: %s, skipping file
2034
2035(S) You requested an inplace edit without creating a backup file. Perl
2036was unable to remove the original file to replace it with the modified
2037file. The file was left unmodified.
2038
2039=item Can't return %s from lvalue subroutine
2040
2041(F) Perl detected an attempt to return illegal lvalues (such
2042as temporary or readonly values) from a subroutine used as an lvalue.
2043This is not allowed.
2044
2045=item Can't weaken a nonreference
2046
2047(F) You attempted to weaken something that was not a reference. Only
2048references can be weakened.
2049
2050=item Character class [:%s:] unknown
2051
2052(F) The class in the character class [: :] syntax is unknown.
437784d6 2053See L<perlre>.
a99ba403
GS
2054
2055=item Character class syntax [%s] belongs inside character classes
2056
ddda08b7 2057(W unsafe) The character class constructs [: :], [= =], and [. .] go
a99ba403 2058I<inside> character classes, the [] are part of the construct,
437784d6
GS
2059for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2060are not currently implemented; they are simply placeholders for
2061future extensions.
a99ba403
GS
2062
2063=item Constant is not %s reference
2064
2065(F) A constant value (perhaps declared using the C<use constant> pragma)
2066is being dereferenced, but it amounts to the wrong type of reference. The
2067message indicates the type of reference that was expected. This usually
2068indicates a syntax error in dereferencing the constant value.
2069See L<perlsub/"Constant Functions"> and L<constant>.
2070
a99ba403
GS
2071=item constant(%s): %s
2072
f0af216f
GS
2073(F) The parser found inconsistencies either while attempting to define an
2074overloaded constant, or when trying to find the character name specified
2075in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
2076C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
a99ba403 2077
6798c92b
GS
2078=item CORE::%s is not a keyword
2079
2080(F) The CORE:: namespace is reserved for Perl keywords.
2081
a99ba403
GS
2082=item defined(@array) is deprecated
2083
2084(D) defined() is not usually useful on arrays because it checks for an
2085undefined I<scalar> value. If you want to see if the array is empty,
2086just use C<if (@array) { # not empty }> for example.
2087
2088=item defined(%hash) is deprecated
2089
2090(D) defined() is not usually useful on hashes because it checks for an
2091undefined I<scalar> value. If you want to see if the hash is empty,
2092just use C<if (%hash) { # not empty }> for example.
2093
2094=item Did not produce a valid header
2095
2096See Server error.
2097
cc507455 2098=item (Did you mean "local" instead of "our"?)
33633739 2099
ddda08b7 2100(W misc) Remember that "our" does not localize the declared global variable.
33633739
GS
2101You have declared it again in the same lexical scope, which seems superfluous.
2102
a99ba403
GS
2103=item Document contains no data
2104
2105See Server error.
2106
2107=item entering effective %s failed
2108
2109(F) While under the C<use filetest> pragma, switching the real and
2110effective uids or gids failed.
6b121555 2111
73b437c8
JH
2112=item false [] range "%s" in regexp
2113
ddda08b7 2114(W regexp) A character class range must start and end at a literal character, not
73b437c8
JH
2115another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2116range is interpreted as a literal "-". Consider quoting the "-", "\-".
2117See L<perlre>.
2118
af8c498a 2119=item Filehandle %s opened only for output
6b121555 2120
ddda08b7 2121(W io) You tried to read from a filehandle opened only for writing. If you
437784d6 2122intended it to be a read/write filehandle, you needed to open it with
c47ff5f1
GS
2123"+<" or "+>" or "+>>" instead of with "<" or nothing. If
2124you intended only to read from the file, use "<". See
af8c498a 2125L<perlfunc/open>.
e02fdbd2 2126
56e90b21
GS
2127=item flock() on closed filehandle %s
2128
ddda08b7 2129(W closed) The filehandle you're attempting to flock() got itself closed some
56e90b21
GS
2130time before now. Check your logic flow. flock() operates on filehandles.
2131Are you attempting to call flock() on a dirhandle by the same name?
2132
2133=item Global symbol "%s" requires explicit package name
2134
2135(F) You've said "use strict vars", which indicates that all variables
2136must either be lexically scoped (using "my"), declared beforehand using
2137"our", or explicitly qualified to say which package the global variable
2138is in (using "::").
2139
a99ba403
GS
2140=item Hexadecimal number > 0xffffffff non-portable
2141
ddda08b7 2142(W portable) The hexadecimal number you specified is larger than 2**32-1
a99ba403
GS
2143(4294967295) and therefore non-portable between systems. See
2144L<perlport> for more on portability concerns.
2145
2146=item Ill-formed CRTL environ value "%s"
2147
ddda08b7 2148(W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
a99ba403 2149environ array, and encountered an element without the C<=> delimiter
4375e838 2150used to separate keys from values. The element is ignored.
a99ba403
GS
2151
2152=item Ill-formed message in prime_env_iter: |%s|
2153
ddda08b7 2154(W internal) A warning peculiar to VMS. Perl tried to read a logical name
a99ba403
GS
2155or CLI symbol definition when preparing to iterate over %ENV, and
2156didn't see the expected delimiter between key and value, so the
2157line was ignored.
2158
2159=item Illegal binary digit %s
2160
437784d6 2161(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
2162
2163=item Illegal binary digit %s ignored
2164
ddda08b7 2165(W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
a99ba403
GS
2166Interpretation of the binary number stopped before the offending digit.
2167
2168=item Illegal number of bits in vec
2169
2170(F) The number of bits in vec() (the third argument) must be a power of
2171two from 1 to 32 (or 64, if your platform supports that).
2172
2173=item Integer overflow in %s number
2174
ddda08b7 2175(W overflow) The hexadecimal, octal or binary number you have specified either
c6edd1b7 2176as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
2177architecture, and has been converted to a floating point number. On a
217832-bit architecture the largest hexadecimal, octal or binary number
2179representable without overflow is 0xFFFFFFFF, 037777777777, or
21800b11111111111111111111111111111111 respectively. Note that Perl
2181transparently promotes all numbers to a floating point representation
2182internally--subject to loss of precision errors in subsequent
2183operations.
2184
09bef843
SB
2185=item Invalid %s attribute: %s
2186
2187The indicated attribute for a subroutine or variable was not recognized
2188by Perl or by a user-supplied handler. See L<attributes>.
2189
2190=item Invalid %s attributes: %s
2191
2192The indicated attributes for a subroutine or variable were not recognized
2193by Perl or by a user-supplied handler. See L<attributes>.
2194
73b437c8
JH
2195=item invalid [] range "%s" in regexp
2196
2197The offending range is now explicitly displayed.
2198
09bef843
SB
2199=item Invalid separator character %s in attribute list
2200
0120eecf 2201(F) Something other than a colon or whitespace was seen between the
09bef843
SB
2202elements of an attribute list. If the previous attribute
2203had a parenthesised parameter list, perhaps that list was terminated
2204too soon. See L<attributes>.
2205
a99ba403
GS
2206=item Invalid separator character %s in subroutine attribute list
2207
0120eecf 2208(F) Something other than a colon or whitespace was seen between the
a99ba403
GS
2209elements of a subroutine attribute list. If the previous attribute
2210had a parenthesised parameter list, perhaps that list was terminated
2211too soon.
2212
2213=item leaving effective %s failed
2214
2215(F) While under the C<use filetest> pragma, switching the real and
2216effective uids or gids failed.
2217
2218=item Lvalue subs returning %s not implemented yet
2219
2220(F) Due to limitations in the current implementation, array and hash
2221values cannot be returned in subroutines used in lvalue context.
2222See L<perlsub/"Lvalue subroutines">.
2223
2224=item Method %s not permitted
2225
2226See Server error.
2227
2228=item Missing %sbrace%s on \N{}
2229
2230(F) Wrong syntax of character name literal C<\N{charname}> within
2231double-quotish context.
2232
06eaf0bc
GS
2233=item Missing command in piped open
2234
ddda08b7 2235(W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
06eaf0bc
GS
2236construction, but the command was missing or blank.
2237
09bef843
SB
2238=item Missing name in "my sub"
2239
2240(F) The reserved syntax for lexically scoped subroutines requires that they
2241have a name with which they can be found.
2242
56e90b21
GS
2243=item No %s specified for -%c
2244
2245(F) The indicated command line switch needs a mandatory argument, but
2246you haven't specified one.
2247
2248=item No package name allowed for variable %s in "our"
2249
2250(F) Fully qualified variable names are not allowed in "our" declarations,
2251because that doesn't make much sense under existing semantics. Such
2252syntax is reserved for future extensions.
2253
2254=item No space allowed after -%c
2255
2256(F) The argument to the indicated command line switch must follow immediately
2257after the switch, without intervening spaces.
2258
a99ba403
GS
2259=item no UTC offset information; assuming local time is UTC
2260
2261(S) A warning peculiar to VMS. Perl was unable to find the local
2262timezone offset, so it's assuming that local system time is equivalent
2263to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2264to translate to the number of seconds which need to be added to UTC to
2265get local time.
2266
2267=item Octal number > 037777777777 non-portable
2268
ddda08b7 2269(W portable) The octal number you specified is larger than 2**32-1 (4294967295)
a99ba403
GS
2270and therefore non-portable between systems. See L<perlport> for more
2271on portability concerns.
2272
2273See also L<perlport> for writing portable code.
2274
2275=item panic: del_backref
2276
2277(P) Failed an internal consistency check while trying to reset a weak
2278reference.
2279
2280=item panic: kid popen errno read
2281
2282(F) forked child returned an incomprehensible message about its errno.
2283
2284=item panic: magic_killbackrefs
2285
2286(P) Failed an internal consistency check while trying to reset all weak
2287references to an object.
2288
56e90b21
GS
2289=item Parentheses missing around "%s" list
2290
ddda08b7 2291(W parenthesis) You said something like
56e90b21
GS
2292
2293 my $foo, $bar = @_;
2294
2295when you meant
2296
2297 my ($foo, $bar) = @_;
2298
54884818 2299Remember that "my", "our", and "local" bind tighter than comma.
56e90b21 2300
a99ba403
GS
2301=item Possible Y2K bug: %s
2302
ddda08b7 2303(W y2k) You are concatenating the number 19 with another number, which
a99ba403
GS
2304could be a potential Year 2000 problem.
2305
8cd79558
GS
2306=item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2307
4375e838 2308(W deprecated) You have written something like this:
8cd79558
GS
2309
2310 sub doit
2311 {
2312 use attrs qw(locked);
2313 }
2314
2315You should use the new declaration syntax instead.
2316
2317 sub doit : locked
2318 {
2319 ...
2320
2321The C<use attrs> pragma is now obsolete, and is only provided for
2322backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2323
2324
a99ba403
GS
2325=item Premature end of script headers
2326
2327See Server error.
2328
0b5b802d
GS
2329=item Repeat count in pack overflows
2330
2331(F) You can't specify a repeat count so large that it overflows
2332your signed integers. See L<perlfunc/pack>.
2333
2334=item Repeat count in unpack overflows
2335
2336(F) You can't specify a repeat count so large that it overflows
2337your signed integers. See L<perlfunc/unpack>.
2338
a99ba403
GS
2339=item realloc() of freed memory ignored
2340
2341(S) An internal routine called realloc() on something that had already
2342been freed.
2343
2344=item Reference is already weak
2345
7a95317d
GS
2346(W misc) You have attempted to weaken a reference that is already weak.
2347Doing so has no effect.
2348
2349=item setpgrp can't take arguments
2350
2351(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2352unlike POSIX setpgid(), which takes a process ID and process group ID.
2353
2354=item Strange *+?{} on zero-length expression
2355
2356(W regexp) You applied a regular expression quantifier in a place where it
2357makes no sense, such as on a zero-width assertion.
2358Try putting the quantifier inside the assertion instead. For example,
2359the way to match "abc" provided that it is followed by three
2360repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2361
2362=item switching effective %s is not implemented
2363
2364(F) While under the C<use filetest> pragma, we cannot switch the
2365real and effective uids or gids.
2366
2367=item This Perl can't reset CRTL environ elements (%s)
2368
2369=item This Perl can't set CRTL environ elements (%s=%s)
2370
2371(W internal) Warnings peculiar to VMS. You tried to change or delete an element
2372of the CRTL's internal environ array, but your copy of Perl wasn't
2373built with a CRTL that contained the setenv() function. You'll need to
2374rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2375L<perlvms>) so that the environ array isn't the target of the change to
2376%ENV which produced the warning.
2377
2378=item Too late to run %s block
2379
2380(W void) A CHECK or INIT block is being defined during run time proper,
2381when the opportunity to run them has already passed. Perhaps you are
2382loading a file with C<require> or C<do> when you should be using
2383C<use> instead. Or perhaps you should put the C<require> or C<do>
2384inside a BEGIN block.
2385
2386=item Unknown open() mode '%s'
2387
2388(F) The second argument of 3-argument open() is not among the list
2389of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2390C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2391
2392=item Unknown process %x sent message to prime_env_iter: %s
2393
2394(P) An error peculiar to VMS. Perl was reading values for %ENV before
2395iterating over it, and someone else stuck a message in the stream of
2396data Perl expected. Someone's very confused, or perhaps trying to
2397subvert Perl's population of %ENV for nefarious purposes.
2398
2399=item Unrecognized escape \\%c passed through
2400
2401(W misc) You used a backslash-character combination which is not recognized
2402by Perl. The character was understood literally.
2403
2404=item Unterminated attribute parameter in attribute list
2405
2406(F) The lexer saw an opening (left) parenthesis character while parsing an
2407attribute list, but the matching closing (right) parenthesis
2408character was not found. You may need to add (or remove) a backslash
2409character to get your parentheses to balance. See L<attributes>.
2410
2411=item Unterminated attribute list
2412
2413(F) The lexer found something other than a simple identifier at the start
2414of an attribute, and it wasn't a semicolon or the start of a
2415block. Perhaps you terminated the parameter list of the previous attribute
2416too soon. See L<attributes>.
2417
2418=item Unterminated attribute parameter in subroutine attribute list
2419
2420(F) The lexer saw an opening (left) parenthesis character while parsing a
2421subroutine attribute list, but the matching closing (right) parenthesis
2422character was not found. You may need to add (or remove) a backslash
2423character to get your parentheses to balance.
2424
2425=item Unterminated subroutine attribute list
2426
2427(F) The lexer found something other than a simple identifier at the start
2428of a subroutine attribute, and it wasn't a semicolon or the start of a
2429block. Perhaps you terminated the parameter list of the previous attribute
2430too soon.
2431
2432=item Value of CLI symbol "%s" too long
2433
2434(W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2435element from a CLI symbol table, and found a resultant string longer
2436than 1024 characters. The return value has been truncated to 1024
2437characters.
2438
2439=item Version number must be a constant number
2440
2441(P) The attempt to translate a C<use Module n.n LIST> statement into
2442its equivalent C<BEGIN> block found an internal inconsistency with
2443the version number.
2444
2445=back
2446
2447=head1 New tests
2448
2449=over 4
2450
2451=item lib/attrs
2452
2453Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
2454
2455=item lib/env
2456
2457Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
2458
2459=item lib/env-array
2460
2461Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
2462
2463=item lib/io_const
2464
2465IO constants (SEEK_*, _IO*).
2466
2467=item lib/io_dir
2468
2469Directory-related IO methods (new, read, close, rewind, tied delete).
2470
2471=item lib/io_multihomed
2472
2473INET sockets with multi-homed hosts.
2474
2475=item lib/io_poll
2476
2477IO poll().
2478
2479=item lib/io_unix
2480
2481UNIX sockets.
2482
2483=item op/attrs
2484
2485Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
2486
2487=item op/filetest
2488
2489File test operators.
2490
2491=item op/lex_assign
2492
2493Verify operations that access pad objects (lexicals and temporaries).
2494
2495=item op/exists_sub
2496
2497Verify C<exists &sub> operations.
2498
2499=back
2500
2501=head1 Incompatible Changes
2502
2503=head2 Perl Source Incompatibilities
2504
2505Beware that any new warnings that have been added or old ones
2506that have been enhanced are B<not> considered incompatible changes.
2507
2508Since all new warnings must be explicitly requested via the C<-w>
2509switch or the C<warnings> pragma, it is ultimately the programmer's
2510responsibility to ensure that warnings are enabled judiciously.
2511
2512=over 4
2513
2514=item CHECK is a new keyword
2515
2516All subroutine definitions named CHECK are now special. See
2517C</"Support for CHECK blocks"> for more information.
2518
2519=item Treatment of list slices of undef has changed
2520
2521There is a potential incompatibility in the behavior of list slices
2522that are comprised entirely of undefined values.
2523See L</"Behavior of list slices is more consistent">.
2524
2525=head2 Format of $English::PERL_VERSION is different
2526
2527The English module now sets $PERL_VERSION to $^V (a string value) rather
2528than C<$]> (a numeric value). This is a potential incompatibility.
2529Send us a report via perlbug if you are affected by this.
2530
2531See L</"Improved Perl version numbering system"> for the reasons for
2532this change.
2533
2534=item Literals of the form C<1.2.3> parse differently
2535
2536Previously, numeric literals with more than one dot in them were
2537interpreted as a floating point number concatenated with one or more
2538numbers. Such "numbers" are now parsed as strings composed of the
2539specified ordinals.
2540
2541For example, C<print 97.98.99> used to output C<97.9899> in earlier
2542versions, but now prints C<abc>.
2543
2544See L</"Support for strings represented as a vector of ordinals">.
2545
2546=item Possibly changed pseudo-random number generator
2547
2548Perl programs that depend on reproducing a specific set of pseudo-random
2549numbers may now produce different output due to improvements made to the
2550rand() builtin. You can use C<sh Configure -Drandfunc=rand> to obtain
2551the old behavior.
2552
2553See L</"Better pseudo-random number generator">.
2554
2555=item Hashing function for hash keys has changed
2556
2557Even though Perl hashes are not order preserving, the apparently
2558random order encountered when iterating on the contents of a hash
2559is actually determined by the hashing algorithm used. Improvements
2560in the algorithm may yield a random order that is B<different> from
2561that of previous versions, especially when iterating on hashes.
2562
2563See L</"Better worst-case behavior of hashes"> for additional
2564information.
2565
2566=item C<undef> fails on read only values
2567
2568Using the C<undef> operator on a readonly value (such as $1) has
2569the same effect as assigning C<undef> to the readonly value--it
2570throws an exception.
2571
2572=item Close-on-exec bit may be set on pipe and socket handles
2573
2574Pipe and socket handles are also now subject to the close-on-exec
2575behavior determined by the special variable $^F.
2576
2577See L</"More consistent close-on-exec behavior">.
2578
2579=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
2580
2581Perl 5.004 deprecated the interpretation of C<$$1> and
2582similar within interpolated strings to mean C<$$ . "1">,
2583but still allowed it.
2584
2585In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
2586
2587=item delete(), values() and C<\(%h)> operate on aliases to values, not copies
2588
2589delete(), each(), values() and hashes in a list context return the actual
2590values in the hash, instead of copies (as they used to in earlier
2591versions). Typical idioms for using these constructs copy the
2592returned values, but this can make a significant difference when
2593creating references to the returned values. Keys in the hash are still
2594returned as copies when iterating on a hash.
2595
2596See also L</"delete(), each(), values() and hash iteration are faster">.
2597
2598=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
2599
2600vec() generates a run-time error if the BITS argument is not
2601a valid power-of-two integer.
2602
2603=item Text of some diagnostic output has changed
2604
2605Most references to internal Perl operations in diagnostics
2606have been changed to be more descriptive. This may be an
2607issue for programs that may incorrectly rely on the exact
2608text of diagnostics for proper functioning.
2609
2610=item C<%@> has been removed
2611
2612The undocumented special variable C<%@> that used to accumulate
2613"background" errors (such as those that happen in DESTROY())
2614has been removed, because it could potentially result in memory
2615leaks.
2616
2617=item Parenthesized not() behaves like a list operator
a99ba403 2618
7a95317d
GS
2619The C<not> operator now falls under the "if it looks like a function,
2620it behaves like a function" rule.
a99ba403 2621
7a95317d
GS
2622As a result, the parenthesized form can be used with C<grep> and C<map>.
2623The following construct used to be a syntax error before, but it works
2624as expected now:
a99ba403 2625
7a95317d 2626 grep not($_), @things;
a99ba403 2627
7a95317d
GS
2628On the other hand, using C<not> with a literal list slice may not
2629work. The following previously allowed construct:
a99ba403 2630
7a95317d 2631 print not (1,2,3)[0];
a99ba403 2632
7a95317d 2633needs to be written with additional parentheses now:
a99ba403 2634
7a95317d 2635 print not((1,2,3)[0]);
a99ba403 2636
7a95317d 2637The behavior remains unaffected when C<not> is not followed by parentheses.
a99ba403 2638
7a95317d 2639=item Semantics of bareword prototype C<(*)> have changed
a99ba403 2640
7a95317d
GS
2641The semantics of the bareword prototype C<*> have changed. Perl 5.005
2642always coerced simple scalar arguments to a typeglob, which wasn't useful
2643in situations where the subroutine must distinguish between a simple
2644scalar and a typeglob. The new behavior is to not coerce bareword
2645arguments to a typeglob. The value will always be visible as either
2646a simple scalar or as a reference to a typeglob.
ddda08b7 2647
7a95317d 2648See L</"More functional bareword prototype (*)">.
ddda08b7 2649
7a95317d 2650=head2 Semantics of bit operators may have changed on 64-bit platforms
a99ba403 2651
7a95317d
GS
2652If your platform is either natively 64-bit or if Perl has been
2653configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
2654there may be a potential incompatibility in the behavior of bitwise
2655numeric operators (& | ^ ~ << >>). These operators used to strictly
2656operate on the lower 32 bits of integers in previous versions, but now
2657operate over the entire native integral width. In particular, note
2658that unary C<~> will produce different results on platforms that have
2659different $Config{ivsize}. For portability, be sure to mask off
2660the excess bits in the result of unary C<~>, e.g., C<~$x & 0xffffffff>.
a99ba403 2661
7a95317d 2662See L</"Bit operators support full native integer width">.
a99ba403 2663
7a95317d 2664=head2 More builtins taint their results
a99ba403 2665
7a95317d
GS
2666As described in L</"Improved security features">, there may be more
2667sources of taint in a Perl program.
af8c498a 2668
7a95317d
GS
2669To avoid these new tainting behaviors, you can build Perl with the
2670Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the
2671ensuing perl binary may be insecure.
af8c498a 2672
7a95317d 2673=back
09bef843 2674
7a95317d 2675=head2 C Source Incompatibilities
09bef843 2676
7a95317d 2677=over 4
09bef843 2678
7a95317d 2679=item C<PERL_POLLUTE>
09bef843 2680
7a95317d
GS
2681Release 5.005 grandfathered old global symbol names by providing preprocessor
2682macros for extension source compatibility. As of release 5.6.0, these
2683preprocessor definitions are not available by default. You need to explicitly
2684compile perl with C<-DPERL_POLLUTE> to get these definitions. For
2685extensions still using the old symbols, this option can be
2686specified via MakeMaker:
09bef843 2687
7a95317d 2688 perl Makefile.PL POLLUTE=1
09bef843 2689
7a95317d 2690=item C<PERL_IMPLICIT_CONTEXT>
09bef843 2691
7a95317d
GS
2692This new build option provides a set of macros for all API functions
2693such that an implicit interpreter/thread context argument is passed to
2694every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2695amounts to a macro invocation that actually translates to something like
2696C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
2697to not have any significant source compatibility issues, the difference
2698between a macro and a real function call will need to be considered.
09bef843 2699
7a95317d
GS
2700This means that there B<is> a source compatibility issue as a result of
2701this if your extensions attempt to use pointers to any of the Perl API
2702functions.
eb6e2d6f 2703
7a95317d
GS
2704Note that the above issue is not relevant to the default build of
2705Perl, whose interfaces continue to match those of prior versions
2706(but subject to the other options described here).
eb6e2d6f 2707
7a95317d
GS
2708See L<perlguts/"The Perl API"> for detailed information on the
2709ramifications of building Perl with this option.
ba8251e8 2710
7a95317d
GS
2711 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
2712 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
2713 intended to be enabled by users at this time.
a99ba403 2714
7a95317d 2715=item C<PERL_POLLUTE_MALLOC>
27806c82 2716
7a95317d
GS
2717Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
2718the system's malloc family of functions to be usurped by the Perl versions,
2719since by default they used the same names. Besides causing problems on
2720platforms that do not allow these functions to be cleanly replaced, this
2721also meant that the system versions could not be called in programs that
2722used Perl's malloc. Previous versions of Perl have allowed this behaviour
2723to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
2724definitions.
3175b8cd 2725
7a95317d
GS
2726As of release 5.6.0, Perl's malloc family of functions have default names
2727distinct from the system versions. You need to explicitly compile perl with
2728C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
2729and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
2730the default.
a99ba403 2731
7a95317d
GS
2732Note that these functions do B<not> constitute Perl's memory allocation API.
2733See L<perlguts/"Memory Allocation"> for further information about that.
a99ba403 2734
7a95317d 2735=back
a99ba403 2736
7a95317d 2737=head2 Compatible C Source API Changes
a99ba403 2738
7a95317d 2739=over
a99ba403 2740
7a95317d 2741=item C<PATCHLEVEL> is now C<PERL_VERSION>
34d09196 2742
7a95317d
GS
2743The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
2744are now available by default from perl.h, and reflect the base revision,
2745patchlevel, and subversion respectively. C<PERL_REVISION> had no
2746prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
2747previously available as C<PATCHLEVEL> and C<SUBVERSION>.
34d09196 2748
7a95317d
GS
2749The new names cause less pollution of the B<cpp> namespace and reflect what
2750the numbers have come to stand for in common practice. For compatibility,
2751the old names are still supported when F<patchlevel.h> is explicitly
2752included (as required before), so there is no source incompatibility
2753from the change.
34d09196 2754
7a95317d 2755=back
a99ba403 2756
7a95317d 2757=head2 Binary Incompatibilities
a99ba403 2758
7a95317d
GS
2759In general, the default build of this release is expected to be binary
2760compatible for extensions built with the 5.005 release or its maintenance
2761versions. However, specific platforms may have broken binary compatibility
2762due to changes in the defaults used in hints files. Therefore, please be
2763sure to always check the platform-specific README files for any notes to
2764the contrary.
a99ba403 2765
7a95317d
GS
2766The usethreads or usemultiplicity builds are B<not> binary compatible
2767with the corresponding builds in 5.005.
a99ba403 2768
7a95317d
GS
2769On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
2770among others), purely internal symbols such as parser functions and the
2771run time opcodes are not exported by default. Perl 5.005 used to export
2772all functions irrespective of whether they were considered part of the
2773public API or not.
a99ba403 2774
7a95317d 2775For the full list of public API functions, see L<perlapi>.
3175b8cd 2776
fc641c2d
JH
2777=head1 Known Problems
2778
227e8dd4 2779=head2 Thread test failures
fc641c2d 2780
97017a80 2781The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
227e8dd4
GS
2782fundamental problems in the 5.005 threading implementation. These are
2783not new failures--Perl 5.005_0x has the same bugs, but didn't have these
2784tests.
fc641c2d
JH
2785
2786=head2 EBCDIC platforms not supported
2787
227e8dd4
GS
2788In earlier releases of Perl, EBCDIC environments like OS390 (also
2789known as Open Edition MVS) and VM-ESA were supported. Due to changes
2790required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
2791supported in Perl 5.6.0.
fc641c2d 2792
d57b1ce7
GS
2793=head2 In 64-bit HP-UX the lib/io_multihomed test may hang
2794
2795The lib/io_multihomed test may hang in HP-UX if Perl has been
2796configured to be 64-bit. Because other 64-bit platforms do not
2797hang in this test, HP-UX is suspect. All other tests pass
2798in 64-bit HP-UX. The test attempts to create and connect to
2799"multihomed" sockets (sockets which have multiple IP addresses).
2800
f46deeb4
JH
2801=head2 NEXTSTEP 3.3 POSIX test failure
2802
2803In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
2804operating system libraries is buggy: the %j format numbers the days of
2805a month starting from zero, which, while being logical to programmers,
2806will cause the subtests 19 to 27 of the lib/posix test may fail.
2807
2cae8c0d
JH
2808=head2 Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc
2809
2810If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
2811The cure is to use the vendor cc, it comes with the operating system
2812and produces good code.
2813
fc641c2d
JH
2814=head2 UNICOS/mk CC failures during Configure run
2815
2816In UNICOS/mk the following errors may appear during the Configure run:
2817
2818 Guessing which symbols your C compiler and preprocessor define...
2819 CC-20 cc: ERROR File = try.c, Line = 3
2820 ...
2821 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
2822 ...
2823 4 errors detected in the compilation of "try.c".
2824
2825The culprit is the broken awk of UNICOS/mk. The effect is fortunately
2826rather mild: Perl itself is not adversely affected by the error, only
2827the h2ph utility coming with Perl, and that is rather rarely needed
2828these days.
2829
14190b26
GS
2830=head2 Arrow operator and arrays
2831
2832When the left argument to the arrow operator C<< -> >> is an array, or
2833the C<scalar> operator operating on an array, the result of the
2834operation must be considered erroneous. For example:
2835
2836 @x->[2]
2837 scalar(@x)->[2]
2838
2839These expressions will get run-time errors in some future release of
2840Perl.
2841
807d88e1
GS
2842=head2 Windows 2000
2843
2844Windows 2000 is known to fail test 22 in lib/open3.t (cause unknown at
2845this time). That test passes under Windows NT.
2846
4bca7e4f 2847=head2 Experimental features
fc641c2d 2848
227e8dd4
GS
2849As discussed above, many features are still experimental. Interfaces and
2850implementation of these features are subject to change, and in extreme cases,
2851even subject to removal in some future release of Perl. These features
2852include the following:
fc641c2d
JH
2853
2854=over 4
2855
2856=item Threads
2857
2858=item Unicode
2859
4bca7e4f
GS
2860=item 64-bit support
2861
fc641c2d
JH
2862=item Lvalue subroutines
2863
2864=item Weak references
2865
4bca7e4f 2866=item The pseudo-hash data type
fc641c2d
JH
2867
2868=item The Compiler suite
2869
4bca7e4f
GS
2870=item Internal implementation of file globbing
2871
227e8dd4 2872=item The DB module
fc641c2d 2873
227e8dd4 2874=item The regular expression constructs C<(?{ code })> and C<(??{ code })>
fc641c2d
JH
2875
2876=back
2877
7a95317d
GS
2878=head1 Obsolete Diagnostics
2879
2880=over 4
2881
2882=item Character class syntax [: :] is reserved for future extensions
2883
2884(W) Within regular expression character classes ([]) the syntax beginning
2885with "[:" and ending with ":]" is reserved for future extensions.
2886If you need to represent those character sequences inside a regular
2887expression character class, just quote the square brackets with the
2888backslash: "\[:" and ":\]".
2889
2890=item Ill-formed logical name |%s| in prime_env_iter
2891
2892(W) A warning peculiar to VMS. A logical name was encountered when preparing
2893to iterate over %ENV which violates the syntactic rules governing logical
2894names. Because it cannot be translated normally, it is skipped, and will not
2895appear in %ENV. This may be a benign occurrence, as some software packages
2896might directly modify logical name tables and introduce nonstandard names,
2897or it may indicate that a logical name table has been corrupted.
2898
2899=item Probable precedence problem on %s
2900
2901(W) The compiler found a bareword where it expected a conditional,
2902which often indicates that an || or && was parsed as part of the
2903last argument of the previous construct, for example:
2904
2905 open FOO || die;
2906
2907=item regexp too big
2908
2909(F) The current implementation of regular expressions uses shorts as
2910address offsets within a string. Unfortunately this means that if
2911the regular expression compiles to longer than 32767, it'll blow up.
2912Usually when you want a regular expression this big, there is a better
2913way to do it with multiple statements. See L<perlre>.
2914
2915=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2916
2917(D) Perl versions before 5.004 misinterpreted any type marker followed
2918by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2919"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2920
2921However, the developers of Perl 5.004 could not fix this bug completely,
2922because at least two widely-used modules depend on the old meaning of
2923"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2924old (broken) way inside strings; but it generates this message as a
2925warning. And in Perl 5.005, this special treatment will cease.
2926
2927=back
2928
2929=head1 Reporting Bugs
ba8251e8 2930
437784d6 2931If you find what you think is a bug, you might check the
14218588 2932articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
GS
2933There may also be information at http://www.perl.com/perl/, the Perl
2934Home Page.
2935
2936If you believe you have an unreported bug, please run the B<perlbug>
642f9deb 2937program included with your release. Be sure to trim your bug down
ba8251e8 2938to a tiny but sufficient test case. Your bug report, along with the
14218588 2939output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
GS
2940analysed by the Perl porting team.
2941
2942=head1 SEE ALSO
2943
2944The F<Changes> file for exhaustive details on what changed.
2945
2946The F<INSTALL> file for how to build Perl.
2947
2948The F<README> file for general stuff.
2949
2950The F<Artistic> and F<Copying> files for copyright information.
2951
2952=head1 HISTORY
2953
a5222a85
GS
2954Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2955contributions from The Perl Porters.
ba8251e8
GS
2956
2957Send omissions or corrections to <F<perlbug@perl.com>>.
2958
2959=cut