1 | =head1 NAME
|
---|
2 |
|
---|
3 | perl5004delta - what's new for perl5.004
|
---|
4 |
|
---|
5 | =head1 DESCRIPTION
|
---|
6 |
|
---|
7 | This document describes differences between the 5.003 release (as
|
---|
8 | documented in I<Programming Perl>, second edition--the Camel Book) and
|
---|
9 | this one.
|
---|
10 |
|
---|
11 | =head1 Supported Environments
|
---|
12 |
|
---|
13 | Perl5.004 builds out of the box on Unix, Plan 9, LynxOS, VMS, OS/2,
|
---|
14 | QNX, AmigaOS, and Windows NT. Perl runs on Windows 95 as well, but it
|
---|
15 | cannot be built there, for lack of a reasonable command interpreter.
|
---|
16 |
|
---|
17 | =head1 Core Changes
|
---|
18 |
|
---|
19 | Most importantly, many bugs were fixed, including several security
|
---|
20 | problems. See the F<Changes> file in the distribution for details.
|
---|
21 |
|
---|
22 | =head2 List assignment to %ENV works
|
---|
23 |
|
---|
24 | C<%ENV = ()> and C<%ENV = @list> now work as expected (except on VMS
|
---|
25 | where it generates a fatal error).
|
---|
26 |
|
---|
27 | =head2 Change to "Can't locate Foo.pm in @INC" error
|
---|
28 |
|
---|
29 | The error "Can't locate Foo.pm in @INC" now lists the contents of @INC
|
---|
30 | for easier debugging.
|
---|
31 |
|
---|
32 | =head2 Compilation option: Binary compatibility with 5.003
|
---|
33 |
|
---|
34 | There is a new Configure question that asks if you want to maintain
|
---|
35 | binary compatibility with Perl 5.003. If you choose binary
|
---|
36 | compatibility, you do not have to recompile your extensions, but you
|
---|
37 | might have symbol conflicts if you embed Perl in another application,
|
---|
38 | just as in the 5.003 release. By default, binary compatibility
|
---|
39 | is preserved at the expense of symbol table pollution.
|
---|
40 |
|
---|
41 | =head2 $PERL5OPT environment variable
|
---|
42 |
|
---|
43 | You may now put Perl options in the $PERL5OPT environment variable.
|
---|
44 | Unless Perl is running with taint checks, it will interpret this
|
---|
45 | variable as if its contents had appeared on a "#!perl" line at the
|
---|
46 | beginning of your script, except that hyphens are optional. PERL5OPT
|
---|
47 | may only be used to set the following switches: B<-[DIMUdmw]>.
|
---|
48 |
|
---|
49 | =head2 Limitations on B<-M>, B<-m>, and B<-T> options
|
---|
50 |
|
---|
51 | The C<-M> and C<-m> options are no longer allowed on the C<#!> line of
|
---|
52 | a script. If a script needs a module, it should invoke it with the
|
---|
53 | C<use> pragma.
|
---|
54 |
|
---|
55 | The B<-T> option is also forbidden on the C<#!> line of a script,
|
---|
56 | unless it was present on the Perl command line. Due to the way C<#!>
|
---|
57 | works, this usually means that B<-T> must be in the first argument.
|
---|
58 | Thus:
|
---|
59 |
|
---|
60 | #!/usr/bin/perl -T -w
|
---|
61 |
|
---|
62 | will probably work for an executable script invoked as C<scriptname>,
|
---|
63 | while:
|
---|
64 |
|
---|
65 | #!/usr/bin/perl -w -T
|
---|
66 |
|
---|
67 | will probably fail under the same conditions. (Non-Unix systems will
|
---|
68 | probably not follow this rule.) But C<perl scriptname> is guaranteed
|
---|
69 | to fail, since then there is no chance of B<-T> being found on the
|
---|
70 | command line before it is found on the C<#!> line.
|
---|
71 |
|
---|
72 | =head2 More precise warnings
|
---|
73 |
|
---|
74 | If you removed the B<-w> option from your Perl 5.003 scripts because it
|
---|
75 | made Perl too verbose, we recommend that you try putting it back when
|
---|
76 | you upgrade to Perl 5.004. Each new perl version tends to remove some
|
---|
77 | undesirable warnings, while adding new warnings that may catch bugs in
|
---|
78 | your scripts.
|
---|
79 |
|
---|
80 | =head2 Deprecated: Inherited C<AUTOLOAD> for non-methods
|
---|
81 |
|
---|
82 | Before Perl 5.004, C<AUTOLOAD> functions were looked up as methods
|
---|
83 | (using the C<@ISA> hierarchy), even when the function to be autoloaded
|
---|
84 | was called as a plain function (e.g. C<Foo::bar()>), not a method
|
---|
85 | (e.g. C<< Foo->bar() >> or C<< $obj->bar() >>).
|
---|
86 |
|
---|
87 | Perl 5.005 will use method lookup only for methods' C<AUTOLOAD>s.
|
---|
88 | However, there is a significant base of existing code that may be using
|
---|
89 | the old behavior. So, as an interim step, Perl 5.004 issues an optional
|
---|
90 | warning when a non-method uses an inherited C<AUTOLOAD>.
|
---|
91 |
|
---|
92 | The simple rule is: Inheritance will not work when autoloading
|
---|
93 | non-methods. The simple fix for old code is: In any module that used to
|
---|
94 | depend on inheriting C<AUTOLOAD> for non-methods from a base class named
|
---|
95 | C<BaseClass>, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup.
|
---|
96 |
|
---|
97 | =head2 Previously deprecated %OVERLOAD is no longer usable
|
---|
98 |
|
---|
99 | Using %OVERLOAD to define overloading was deprecated in 5.003.
|
---|
100 | Overloading is now defined using the overload pragma. %OVERLOAD is
|
---|
101 | still used internally but should not be used by Perl scripts. See
|
---|
102 | L<overload> for more details.
|
---|
103 |
|
---|
104 | =head2 Subroutine arguments created only when they're modified
|
---|
105 |
|
---|
106 | In Perl 5.004, nonexistent array and hash elements used as subroutine
|
---|
107 | parameters are brought into existence only if they are actually
|
---|
108 | assigned to (via C<@_>).
|
---|
109 |
|
---|
110 | Earlier versions of Perl vary in their handling of such arguments.
|
---|
111 | Perl versions 5.002 and 5.003 always brought them into existence.
|
---|
112 | Perl versions 5.000 and 5.001 brought them into existence only if
|
---|
113 | they were not the first argument (which was almost certainly a bug).
|
---|
114 | Earlier versions of Perl never brought them into existence.
|
---|
115 |
|
---|
116 | For example, given this code:
|
---|
117 |
|
---|
118 | undef @a; undef %a;
|
---|
119 | sub show { print $_[0] };
|
---|
120 | sub change { $_[0]++ };
|
---|
121 | show($a[2]);
|
---|
122 | change($a{b});
|
---|
123 |
|
---|
124 | After this code executes in Perl 5.004, $a{b} exists but $a[2] does
|
---|
125 | not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed
|
---|
126 | (but $a[2]'s value would have been undefined).
|
---|
127 |
|
---|
128 | =head2 Group vector changeable with C<$)>
|
---|
129 |
|
---|
130 | The C<$)> special variable has always (well, in Perl 5, at least)
|
---|
131 | reflected not only the current effective group, but also the group list
|
---|
132 | as returned by the C<getgroups()> C function (if there is one).
|
---|
133 | However, until this release, there has not been a way to call the
|
---|
134 | C<setgroups()> C function from Perl.
|
---|
135 |
|
---|
136 | In Perl 5.004, assigning to C<$)> is exactly symmetrical with examining
|
---|
137 | it: The first number in its string value is used as the effective gid;
|
---|
138 | if there are any numbers after the first one, they are passed to the
|
---|
139 | C<setgroups()> C function (if there is one).
|
---|
140 |
|
---|
141 | =head2 Fixed parsing of $$<digit>, &$<digit>, etc.
|
---|
142 |
|
---|
143 | Perl versions before 5.004 misinterpreted any type marker followed by
|
---|
144 | "$" and a digit. For example, "$$0" was incorrectly taken to mean
|
---|
145 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
|
---|
146 |
|
---|
147 | However, the developers of Perl 5.004 could not fix this bug completely,
|
---|
148 | because at least two widely-used modules depend on the old meaning of
|
---|
149 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
|
---|
150 | old (broken) way inside strings; but it generates this message as a
|
---|
151 | warning. And in Perl 5.005, this special treatment will cease.
|
---|
152 |
|
---|
153 | =head2 Fixed localization of $<digit>, $&, etc.
|
---|
154 |
|
---|
155 | Perl versions before 5.004 did not always properly localize the
|
---|
156 | regex-related special variables. Perl 5.004 does localize them, as
|
---|
157 | the documentation has always said it should. This may result in $1,
|
---|
158 | $2, etc. no longer being set where existing programs use them.
|
---|
159 |
|
---|
160 | =head2 No resetting of $. on implicit close
|
---|
161 |
|
---|
162 | The documentation for Perl 5.0 has always stated that C<$.> is I<not>
|
---|
163 | reset when an already-open file handle is reopened with no intervening
|
---|
164 | call to C<close>. Due to a bug, perl versions 5.000 through 5.003
|
---|
165 | I<did> reset C<$.> under that circumstance; Perl 5.004 does not.
|
---|
166 |
|
---|
167 | =head2 C<wantarray> may return undef
|
---|
168 |
|
---|
169 | The C<wantarray> operator returns true if a subroutine is expected to
|
---|
170 | return a list, and false otherwise. In Perl 5.004, C<wantarray> can
|
---|
171 | also return the undefined value if a subroutine's return value will
|
---|
172 | not be used at all, which allows subroutines to avoid a time-consuming
|
---|
173 | calculation of a return value if it isn't going to be used.
|
---|
174 |
|
---|
175 | =head2 C<eval EXPR> determines value of EXPR in scalar context
|
---|
176 |
|
---|
177 | Perl (version 5) used to determine the value of EXPR inconsistently,
|
---|
178 | sometimes incorrectly using the surrounding context for the determination.
|
---|
179 | Now, the value of EXPR (before being parsed by eval) is always determined in
|
---|
180 | a scalar context. Once parsed, it is executed as before, by providing
|
---|
181 | the context that the scope surrounding the eval provided. This change
|
---|
182 | makes the behavior Perl4 compatible, besides fixing bugs resulting from
|
---|
183 | the inconsistent behavior. This program:
|
---|
184 |
|
---|
185 | @a = qw(time now is time);
|
---|
186 | print eval @a;
|
---|
187 | print '|', scalar eval @a;
|
---|
188 |
|
---|
189 | used to print something like "timenowis881399109|4", but now (and in perl4)
|
---|
190 | prints "4|4".
|
---|
191 |
|
---|
192 | =head2 Changes to tainting checks
|
---|
193 |
|
---|
194 | A bug in previous versions may have failed to detect some insecure
|
---|
195 | conditions when taint checks are turned on. (Taint checks are used
|
---|
196 | in setuid or setgid scripts, or when explicitly turned on with the
|
---|
197 | C<-T> invocation option.) Although it's unlikely, this may cause a
|
---|
198 | previously-working script to now fail -- which should be construed
|
---|
199 | as a blessing, since that indicates a potentially-serious security
|
---|
200 | hole was just plugged.
|
---|
201 |
|
---|
202 | The new restrictions when tainting include:
|
---|
203 |
|
---|
204 | =over 4
|
---|
205 |
|
---|
206 | =item No glob() or <*>
|
---|
207 |
|
---|
208 | These operators may spawn the C shell (csh), which cannot be made
|
---|
209 | safe. This restriction will be lifted in a future version of Perl
|
---|
210 | when globbing is implemented without the use of an external program.
|
---|
211 |
|
---|
212 | =item No spawning if tainted $CDPATH, $ENV, $BASH_ENV
|
---|
213 |
|
---|
214 | These environment variables may alter the behavior of spawned programs
|
---|
215 | (especially shells) in ways that subvert security. So now they are
|
---|
216 | treated as dangerous, in the manner of $IFS and $PATH.
|
---|
217 |
|
---|
218 | =item No spawning if tainted $TERM doesn't look like a terminal name
|
---|
219 |
|
---|
220 | Some termcap libraries do unsafe things with $TERM. However, it would be
|
---|
221 | unnecessarily harsh to treat all $TERM values as unsafe, since only shell
|
---|
222 | metacharacters can cause trouble in $TERM. So a tainted $TERM is
|
---|
223 | considered to be safe if it contains only alphanumerics, underscores,
|
---|
224 | dashes, and colons, and unsafe if it contains other characters (including
|
---|
225 | whitespace).
|
---|
226 |
|
---|
227 | =back
|
---|
228 |
|
---|
229 | =head2 New Opcode module and revised Safe module
|
---|
230 |
|
---|
231 | A new Opcode module supports the creation, manipulation and
|
---|
232 | application of opcode masks. The revised Safe module has a new API
|
---|
233 | and is implemented using the new Opcode module. Please read the new
|
---|
234 | Opcode and Safe documentation.
|
---|
235 |
|
---|
236 | =head2 Embedding improvements
|
---|
237 |
|
---|
238 | In older versions of Perl it was not possible to create more than one
|
---|
239 | Perl interpreter instance inside a single process without leaking like a
|
---|
240 | sieve and/or crashing. The bugs that caused this behavior have all been
|
---|
241 | fixed. However, you still must take care when embedding Perl in a C
|
---|
242 | program. See the updated perlembed manpage for tips on how to manage
|
---|
243 | your interpreters.
|
---|
244 |
|
---|
245 | =head2 Internal change: FileHandle class based on IO::* classes
|
---|
246 |
|
---|
247 | File handles are now stored internally as type IO::Handle. The
|
---|
248 | FileHandle module is still supported for backwards compatibility, but
|
---|
249 | it is now merely a front end to the IO::* modules -- specifically,
|
---|
250 | IO::Handle, IO::Seekable, and IO::File. We suggest, but do not
|
---|
251 | require, that you use the IO::* modules in new code.
|
---|
252 |
|
---|
253 | In harmony with this change, C<*GLOB{FILEHANDLE}> is now just a
|
---|
254 | backward-compatible synonym for C<*GLOB{IO}>.
|
---|
255 |
|
---|
256 | =head2 Internal change: PerlIO abstraction interface
|
---|
257 |
|
---|
258 | It is now possible to build Perl with AT&T's sfio IO package
|
---|
259 | instead of stdio. See L<perlapio> for more details, and
|
---|
260 | the F<INSTALL> file for how to use it.
|
---|
261 |
|
---|
262 | =head2 New and changed syntax
|
---|
263 |
|
---|
264 | =over 4
|
---|
265 |
|
---|
266 | =item $coderef->(PARAMS)
|
---|
267 |
|
---|
268 | A subroutine reference may now be suffixed with an arrow and a
|
---|
269 | (possibly empty) parameter list. This syntax denotes a call of the
|
---|
270 | referenced subroutine, with the given parameters (if any).
|
---|
271 |
|
---|
272 | This new syntax follows the pattern of S<C<< $hashref->{FOO} >>> and
|
---|
273 | S<C<< $aryref->[$foo] >>>: You may now write S<C<&$subref($foo)>> as
|
---|
274 | S<C<< $subref->($foo) >>>. All these arrow terms may be chained;
|
---|
275 | thus, S<C<< &{$table->{FOO}}($bar) >>> may now be written
|
---|
276 | S<C<< $table->{FOO}->($bar) >>>.
|
---|
277 |
|
---|
278 | =back
|
---|
279 |
|
---|
280 | =head2 New and changed builtin constants
|
---|
281 |
|
---|
282 | =over 4
|
---|
283 |
|
---|
284 | =item __PACKAGE__
|
---|
285 |
|
---|
286 | The current package name at compile time, or the undefined value if
|
---|
287 | there is no current package (due to a C<package;> directive). Like
|
---|
288 | C<__FILE__> and C<__LINE__>, C<__PACKAGE__> does I<not> interpolate
|
---|
289 | into strings.
|
---|
290 |
|
---|
291 | =back
|
---|
292 |
|
---|
293 | =head2 New and changed builtin variables
|
---|
294 |
|
---|
295 | =over 4
|
---|
296 |
|
---|
297 | =item $^E
|
---|
298 |
|
---|
299 | Extended error message on some platforms. (Also known as
|
---|
300 | $EXTENDED_OS_ERROR if you C<use English>).
|
---|
301 |
|
---|
302 | =item $^H
|
---|
303 |
|
---|
304 | The current set of syntax checks enabled by C<use strict>. See the
|
---|
305 | documentation of C<strict> for more details. Not actually new, but
|
---|
306 | newly documented.
|
---|
307 | Because it is intended for internal use by Perl core components,
|
---|
308 | there is no C<use English> long name for this variable.
|
---|
309 |
|
---|
310 | =item $^M
|
---|
311 |
|
---|
312 | By default, running out of memory it is not trappable. However, if
|
---|
313 | compiled for this, Perl may use the contents of C<$^M> as an emergency
|
---|
314 | pool after die()ing with this message. Suppose that your Perl were
|
---|
315 | compiled with -DPERL_EMERGENCY_SBRK and used Perl's malloc. Then
|
---|
316 |
|
---|
317 | $^M = 'a' x (1<<16);
|
---|
318 |
|
---|
319 | would allocate a 64K buffer for use when in emergency.
|
---|
320 | See the F<INSTALL> file for information on how to enable this option.
|
---|
321 | As a disincentive to casual use of this advanced feature,
|
---|
322 | there is no C<use English> long name for this variable.
|
---|
323 |
|
---|
324 | =back
|
---|
325 |
|
---|
326 | =head2 New and changed builtin functions
|
---|
327 |
|
---|
328 | =over 4
|
---|
329 |
|
---|
330 | =item delete on slices
|
---|
331 |
|
---|
332 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>)
|
---|
333 |
|
---|
334 | =item flock
|
---|
335 |
|
---|
336 | is now supported on more platforms, prefers fcntl to lockf when
|
---|
337 | emulating, and always flushes before (un)locking.
|
---|
338 |
|
---|
339 | =item printf and sprintf
|
---|
340 |
|
---|
341 | Perl now implements these functions itself; it doesn't use the C
|
---|
342 | library function sprintf() any more, except for floating-point
|
---|
343 | numbers, and even then only known flags are allowed. As a result, it
|
---|
344 | is now possible to know which conversions and flags will work, and
|
---|
345 | what they will do.
|
---|
346 |
|
---|
347 | The new conversions in Perl's sprintf() are:
|
---|
348 |
|
---|
349 | %i a synonym for %d
|
---|
350 | %p a pointer (the address of the Perl value, in hexadecimal)
|
---|
351 | %n special: *stores* the number of characters output so far
|
---|
352 | into the next variable in the parameter list
|
---|
353 |
|
---|
354 | The new flags that go between the C<%> and the conversion are:
|
---|
355 |
|
---|
356 | # prefix octal with "0", hex with "0x"
|
---|
357 | h interpret integer as C type "short" or "unsigned short"
|
---|
358 | V interpret integer as Perl's standard integer type
|
---|
359 |
|
---|
360 | Also, where a number would appear in the flags, an asterisk ("*") may
|
---|
361 | be used instead, in which case Perl uses the next item in the
|
---|
362 | parameter list as the given number (that is, as the field width or
|
---|
363 | precision). If a field width obtained through "*" is negative, it has
|
---|
364 | the same effect as the '-' flag: left-justification.
|
---|
365 |
|
---|
366 | See L<perlfunc/sprintf> for a complete list of conversion and flags.
|
---|
367 |
|
---|
368 | =item keys as an lvalue
|
---|
369 |
|
---|
370 | As an lvalue, C<keys> allows you to increase the number of hash buckets
|
---|
371 | allocated for the given hash. This can gain you a measure of efficiency if
|
---|
372 | you know the hash is going to get big. (This is similar to pre-extending
|
---|
373 | an array by assigning a larger number to $#array.) If you say
|
---|
374 |
|
---|
375 | keys %hash = 200;
|
---|
376 |
|
---|
377 | then C<%hash> will have at least 200 buckets allocated for it. These
|
---|
378 | buckets will be retained even if you do C<%hash = ()>; use C<undef
|
---|
379 | %hash> if you want to free the storage while C<%hash> is still in scope.
|
---|
380 | You can't shrink the number of buckets allocated for the hash using
|
---|
381 | C<keys> in this way (but you needn't worry about doing this by accident,
|
---|
382 | as trying has no effect).
|
---|
383 |
|
---|
384 | =item my() in Control Structures
|
---|
385 |
|
---|
386 | You can now use my() (with or without the parentheses) in the control
|
---|
387 | expressions of control structures such as:
|
---|
388 |
|
---|
389 | while (defined(my $line = <>)) {
|
---|
390 | $line = lc $line;
|
---|
391 | } continue {
|
---|
392 | print $line;
|
---|
393 | }
|
---|
394 |
|
---|
395 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) {
|
---|
396 | user_agrees();
|
---|
397 | } elsif ($answer =~ /^n(o)?$/i) {
|
---|
398 | user_disagrees();
|
---|
399 | } else {
|
---|
400 | chomp $answer;
|
---|
401 | die "`$answer' is neither `yes' nor `no'";
|
---|
402 | }
|
---|
403 |
|
---|
404 | Also, you can declare a foreach loop control variable as lexical by
|
---|
405 | preceding it with the word "my". For example, in:
|
---|
406 |
|
---|
407 | foreach my $i (1, 2, 3) {
|
---|
408 | some_function();
|
---|
409 | }
|
---|
410 |
|
---|
411 | $i is a lexical variable, and the scope of $i extends to the end of
|
---|
412 | the loop, but not beyond it.
|
---|
413 |
|
---|
414 | Note that you still cannot use my() on global punctuation variables
|
---|
415 | such as $_ and the like.
|
---|
416 |
|
---|
417 | =item pack() and unpack()
|
---|
418 |
|
---|
419 | A new format 'w' represents a BER compressed integer (as defined in
|
---|
420 | ASN.1). Its format is a sequence of one or more bytes, each of which
|
---|
421 | provides seven bits of the total value, with the most significant
|
---|
422 | first. Bit eight of each byte is set, except for the last byte, in
|
---|
423 | which bit eight is clear.
|
---|
424 |
|
---|
425 | If 'p' or 'P' are given undef as values, they now generate a NULL
|
---|
426 | pointer.
|
---|
427 |
|
---|
428 | Both pack() and unpack() now fail when their templates contain invalid
|
---|
429 | types. (Invalid types used to be ignored.)
|
---|
430 |
|
---|
431 | =item sysseek()
|
---|
432 |
|
---|
433 | The new sysseek() operator is a variant of seek() that sets and gets the
|
---|
434 | file's system read/write position, using the lseek(2) system call. It is
|
---|
435 | the only reliable way to seek before using sysread() or syswrite(). Its
|
---|
436 | return value is the new position, or the undefined value on failure.
|
---|
437 |
|
---|
438 | =item use VERSION
|
---|
439 |
|
---|
440 | If the first argument to C<use> is a number, it is treated as a version
|
---|
441 | number instead of a module name. If the version of the Perl interpreter
|
---|
442 | is less than VERSION, then an error message is printed and Perl exits
|
---|
443 | immediately. Because C<use> occurs at compile time, this check happens
|
---|
444 | immediately during the compilation process, unlike C<require VERSION>,
|
---|
445 | which waits until runtime for the check. This is often useful if you
|
---|
446 | need to check the current Perl version before C<use>ing library modules
|
---|
447 | which have changed in incompatible ways from older versions of Perl.
|
---|
448 | (We try not to do this more than we have to.)
|
---|
449 |
|
---|
450 | =item use Module VERSION LIST
|
---|
451 |
|
---|
452 | If the VERSION argument is present between Module and LIST, then the
|
---|
453 | C<use> will call the VERSION method in class Module with the given
|
---|
454 | version as an argument. The default VERSION method, inherited from
|
---|
455 | the UNIVERSAL class, croaks if the given version is larger than the
|
---|
456 | value of the variable $Module::VERSION. (Note that there is not a
|
---|
457 | comma after VERSION!)
|
---|
458 |
|
---|
459 | This version-checking mechanism is similar to the one currently used
|
---|
460 | in the Exporter module, but it is faster and can be used with modules
|
---|
461 | that don't use the Exporter. It is the recommended method for new
|
---|
462 | code.
|
---|
463 |
|
---|
464 | =item prototype(FUNCTION)
|
---|
465 |
|
---|
466 | Returns the prototype of a function as a string (or C<undef> if the
|
---|
467 | function has no prototype). FUNCTION is a reference to or the name of the
|
---|
468 | function whose prototype you want to retrieve.
|
---|
469 | (Not actually new; just never documented before.)
|
---|
470 |
|
---|
471 | =item srand
|
---|
472 |
|
---|
473 | The default seed for C<srand>, which used to be C<time>, has been changed.
|
---|
474 | Now it's a heady mix of difficult-to-predict system-dependent values,
|
---|
475 | which should be sufficient for most everyday purposes.
|
---|
476 |
|
---|
477 | Previous to version 5.004, calling C<rand> without first calling C<srand>
|
---|
478 | would yield the same sequence of random numbers on most or all machines.
|
---|
479 | Now, when perl sees that you're calling C<rand> and haven't yet called
|
---|
480 | C<srand>, it calls C<srand> with the default seed. You should still call
|
---|
481 | C<srand> manually if your code might ever be run on a pre-5.004 system,
|
---|
482 | of course, or if you want a seed other than the default.
|
---|
483 |
|
---|
484 | =item $_ as Default
|
---|
485 |
|
---|
486 | Functions documented in the Camel to default to $_ now in
|
---|
487 | fact do, and all those that do are so documented in L<perlfunc>.
|
---|
488 |
|
---|
489 | =item C<m//gc> does not reset search position on failure
|
---|
490 |
|
---|
491 | The C<m//g> match iteration construct has always reset its target
|
---|
492 | string's search position (which is visible through the C<pos> operator)
|
---|
493 | when a match fails; as a result, the next C<m//g> match after a failure
|
---|
494 | starts again at the beginning of the string. With Perl 5.004, this
|
---|
495 | reset may be disabled by adding the "c" (for "continue") modifier,
|
---|
496 | i.e. C<m//gc>. This feature, in conjunction with the C<\G> zero-width
|
---|
497 | assertion, makes it possible to chain matches together. See L<perlop>
|
---|
498 | and L<perlre>.
|
---|
499 |
|
---|
500 | =item C<m//x> ignores whitespace before ?*+{}
|
---|
501 |
|
---|
502 | The C<m//x> construct has always been intended to ignore all unescaped
|
---|
503 | whitespace. However, before Perl 5.004, whitespace had the effect of
|
---|
504 | escaping repeat modifiers like "*" or "?"; for example, C</a *b/x> was
|
---|
505 | (mis)interpreted as C</a\*b/x>. This bug has been fixed in 5.004.
|
---|
506 |
|
---|
507 | =item nested C<sub{}> closures work now
|
---|
508 |
|
---|
509 | Prior to the 5.004 release, nested anonymous functions didn't work
|
---|
510 | right. They do now.
|
---|
511 |
|
---|
512 | =item formats work right on changing lexicals
|
---|
513 |
|
---|
514 | Just like anonymous functions that contain lexical variables
|
---|
515 | that change (like a lexical index variable for a C<foreach> loop),
|
---|
516 | formats now work properly. For example, this silently failed
|
---|
517 | before (printed only zeros), but is fine now:
|
---|
518 |
|
---|
519 | my $i;
|
---|
520 | foreach $i ( 1 .. 10 ) {
|
---|
521 | write;
|
---|
522 | }
|
---|
523 | format =
|
---|
524 | my i is @#
|
---|
525 | $i
|
---|
526 | .
|
---|
527 |
|
---|
528 | However, it still fails (without a warning) if the foreach is within a
|
---|
529 | subroutine:
|
---|
530 |
|
---|
531 | my $i;
|
---|
532 | sub foo {
|
---|
533 | foreach $i ( 1 .. 10 ) {
|
---|
534 | write;
|
---|
535 | }
|
---|
536 | }
|
---|
537 | foo;
|
---|
538 | format =
|
---|
539 | my i is @#
|
---|
540 | $i
|
---|
541 | .
|
---|
542 |
|
---|
543 | =back
|
---|
544 |
|
---|
545 | =head2 New builtin methods
|
---|
546 |
|
---|
547 | The C<UNIVERSAL> package automatically contains the following methods that
|
---|
548 | are inherited by all other classes:
|
---|
549 |
|
---|
550 | =over 4
|
---|
551 |
|
---|
552 | =item isa(CLASS)
|
---|
553 |
|
---|
554 | C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS>
|
---|
555 |
|
---|
556 | C<isa> is also exportable and can be called as a sub with two arguments. This
|
---|
557 | allows the ability to check what a reference points to. Example:
|
---|
558 |
|
---|
559 | use UNIVERSAL qw(isa);
|
---|
560 |
|
---|
561 | if(isa($ref, 'ARRAY')) {
|
---|
562 | ...
|
---|
563 | }
|
---|
564 |
|
---|
565 | =item can(METHOD)
|
---|
566 |
|
---|
567 | C<can> checks to see if its object has a method called C<METHOD>,
|
---|
568 | if it does then a reference to the sub is returned; if it does not then
|
---|
569 | I<undef> is returned.
|
---|
570 |
|
---|
571 | =item VERSION( [NEED] )
|
---|
572 |
|
---|
573 | C<VERSION> returns the version number of the class (package). If the
|
---|
574 | NEED argument is given then it will check that the current version (as
|
---|
575 | defined by the $VERSION variable in the given package) not less than
|
---|
576 | NEED; it will die if this is not the case. This method is normally
|
---|
577 | called as a class method. This method is called automatically by the
|
---|
578 | C<VERSION> form of C<use>.
|
---|
579 |
|
---|
580 | use A 1.2 qw(some imported subs);
|
---|
581 | # implies:
|
---|
582 | A->VERSION(1.2);
|
---|
583 |
|
---|
584 | =back
|
---|
585 |
|
---|
586 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and
|
---|
587 | C<isa> uses a very similar method and caching strategy. This may cause
|
---|
588 | strange effects if the Perl code dynamically changes @ISA in any package.
|
---|
589 |
|
---|
590 | You may add other methods to the UNIVERSAL class via Perl or XS code.
|
---|
591 | You do not need to C<use UNIVERSAL> in order to make these methods
|
---|
592 | available to your program. This is necessary only if you wish to
|
---|
593 | have C<isa> available as a plain subroutine in the current package.
|
---|
594 |
|
---|
595 | =head2 TIEHANDLE now supported
|
---|
596 |
|
---|
597 | See L<perltie> for other kinds of tie()s.
|
---|
598 |
|
---|
599 | =over 4
|
---|
600 |
|
---|
601 | =item TIEHANDLE classname, LIST
|
---|
602 |
|
---|
603 | This is the constructor for the class. That means it is expected to
|
---|
604 | return an object of some sort. The reference can be used to
|
---|
605 | hold some internal information.
|
---|
606 |
|
---|
607 | sub TIEHANDLE {
|
---|
608 | print "<shout>\n";
|
---|
609 | my $i;
|
---|
610 | return bless \$i, shift;
|
---|
611 | }
|
---|
612 |
|
---|
613 | =item PRINT this, LIST
|
---|
614 |
|
---|
615 | This method will be triggered every time the tied handle is printed to.
|
---|
616 | Beyond its self reference it also expects the list that was passed to
|
---|
617 | the print function.
|
---|
618 |
|
---|
619 | sub PRINT {
|
---|
620 | $r = shift;
|
---|
621 | $$r++;
|
---|
622 | return print join( $, => map {uc} @_), $\;
|
---|
623 | }
|
---|
624 |
|
---|
625 | =item PRINTF this, LIST
|
---|
626 |
|
---|
627 | This method will be triggered every time the tied handle is printed to
|
---|
628 | with the C<printf()> function.
|
---|
629 | Beyond its self reference it also expects the format and list that was
|
---|
630 | passed to the printf function.
|
---|
631 |
|
---|
632 | sub PRINTF {
|
---|
633 | shift;
|
---|
634 | my $fmt = shift;
|
---|
635 | print sprintf($fmt, @_)."\n";
|
---|
636 | }
|
---|
637 |
|
---|
638 | =item READ this LIST
|
---|
639 |
|
---|
640 | This method will be called when the handle is read from via the C<read>
|
---|
641 | or C<sysread> functions.
|
---|
642 |
|
---|
643 | sub READ {
|
---|
644 | $r = shift;
|
---|
645 | my($buf,$len,$offset) = @_;
|
---|
646 | print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset";
|
---|
647 | }
|
---|
648 |
|
---|
649 | =item READLINE this
|
---|
650 |
|
---|
651 | This method will be called when the handle is read from. The method
|
---|
652 | should return undef when there is no more data.
|
---|
653 |
|
---|
654 | sub READLINE {
|
---|
655 | $r = shift;
|
---|
656 | return "PRINT called $$r times\n"
|
---|
657 | }
|
---|
658 |
|
---|
659 | =item GETC this
|
---|
660 |
|
---|
661 | This method will be called when the C<getc> function is called.
|
---|
662 |
|
---|
663 | sub GETC { print "Don't GETC, Get Perl"; return "a"; }
|
---|
664 |
|
---|
665 | =item DESTROY this
|
---|
666 |
|
---|
667 | As with the other types of ties, this method will be called when the
|
---|
668 | tied handle is about to be destroyed. This is useful for debugging and
|
---|
669 | possibly for cleaning up.
|
---|
670 |
|
---|
671 | sub DESTROY {
|
---|
672 | print "</shout>\n";
|
---|
673 | }
|
---|
674 |
|
---|
675 | =back
|
---|
676 |
|
---|
677 | =head2 Malloc enhancements
|
---|
678 |
|
---|
679 | If perl is compiled with the malloc included with the perl distribution
|
---|
680 | (that is, if C<perl -V:d_mymalloc> is 'define') then you can print
|
---|
681 | memory statistics at runtime by running Perl thusly:
|
---|
682 |
|
---|
683 | env PERL_DEBUG_MSTATS=2 perl your_script_here
|
---|
684 |
|
---|
685 | The value of 2 means to print statistics after compilation and on
|
---|
686 | exit; with a value of 1, the statistics are printed only on exit.
|
---|
687 | (If you want the statistics at an arbitrary time, you'll need to
|
---|
688 | install the optional module Devel::Peek.)
|
---|
689 |
|
---|
690 | Three new compilation flags are recognized by malloc.c. (They have no
|
---|
691 | effect if perl is compiled with system malloc().)
|
---|
692 |
|
---|
693 | =over 4
|
---|
694 |
|
---|
695 | =item -DPERL_EMERGENCY_SBRK
|
---|
696 |
|
---|
697 | If this macro is defined, running out of memory need not be a fatal
|
---|
698 | error: a memory pool can allocated by assigning to the special
|
---|
699 | variable C<$^M>. See L<"$^M">.
|
---|
700 |
|
---|
701 | =item -DPACK_MALLOC
|
---|
702 |
|
---|
703 | Perl memory allocation is by bucket with sizes close to powers of two.
|
---|
704 | Because of these malloc overhead may be big, especially for data of
|
---|
705 | size exactly a power of two. If C<PACK_MALLOC> is defined, perl uses
|
---|
706 | a slightly different algorithm for small allocations (up to 64 bytes
|
---|
707 | long), which makes it possible to have overhead down to 1 byte for
|
---|
708 | allocations which are powers of two (and appear quite often).
|
---|
709 |
|
---|
710 | Expected memory savings (with 8-byte alignment in C<alignbytes>) is
|
---|
711 | about 20% for typical Perl usage. Expected slowdown due to additional
|
---|
712 | malloc overhead is in fractions of a percent (hard to measure, because
|
---|
713 | of the effect of saved memory on speed).
|
---|
714 |
|
---|
715 | =item -DTWO_POT_OPTIMIZE
|
---|
716 |
|
---|
717 | Similarly to C<PACK_MALLOC>, this macro improves allocations of data
|
---|
718 | with size close to a power of two; but this works for big allocations
|
---|
719 | (starting with 16K by default). Such allocations are typical for big
|
---|
720 | hashes and special-purpose scripts, especially image processing.
|
---|
721 |
|
---|
722 | On recent systems, the fact that perl requires 2M from system for 1M
|
---|
723 | allocation will not affect speed of execution, since the tail of such
|
---|
724 | a chunk is not going to be touched (and thus will not require real
|
---|
725 | memory). However, it may result in a premature out-of-memory error.
|
---|
726 | So if you will be manipulating very large blocks with sizes close to
|
---|
727 | powers of two, it would be wise to define this macro.
|
---|
728 |
|
---|
729 | Expected saving of memory is 0-100% (100% in applications which
|
---|
730 | require most memory in such 2**n chunks); expected slowdown is
|
---|
731 | negligible.
|
---|
732 |
|
---|
733 | =back
|
---|
734 |
|
---|
735 | =head2 Miscellaneous efficiency enhancements
|
---|
736 |
|
---|
737 | Functions that have an empty prototype and that do nothing but return
|
---|
738 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>).
|
---|
739 |
|
---|
740 | Each unique hash key is only allocated once, no matter how many hashes
|
---|
741 | have an entry with that key. So even if you have 100 copies of the
|
---|
742 | same hash, the hash keys never have to be reallocated.
|
---|
743 |
|
---|
744 | =head1 Support for More Operating Systems
|
---|
745 |
|
---|
746 | Support for the following operating systems is new in Perl 5.004.
|
---|
747 |
|
---|
748 | =head2 Win32
|
---|
749 |
|
---|
750 | Perl 5.004 now includes support for building a "native" perl under
|
---|
751 | Windows NT, using the Microsoft Visual C++ compiler (versions 2.0
|
---|
752 | and above) or the Borland C++ compiler (versions 5.02 and above).
|
---|
753 | The resulting perl can be used under Windows 95 (if it
|
---|
754 | is installed in the same directory locations as it got installed
|
---|
755 | in Windows NT). This port includes support for perl extension
|
---|
756 | building tools like L<MakeMaker> and L<h2xs>, so that many extensions
|
---|
757 | available on the Comprehensive Perl Archive Network (CPAN) can now be
|
---|
758 | readily built under Windows NT. See http://www.perl.com/ for more
|
---|
759 | information on CPAN and F<README.win32> in the perl distribution for more
|
---|
760 | details on how to get started with building this port.
|
---|
761 |
|
---|
762 | There is also support for building perl under the Cygwin32 environment.
|
---|
763 | Cygwin32 is a set of GNU tools that make it possible to compile and run
|
---|
764 | many Unix programs under Windows NT by providing a mostly Unix-like
|
---|
765 | interface for compilation and execution. See F<README.cygwin32> in the
|
---|
766 | perl distribution for more details on this port and how to obtain the
|
---|
767 | Cygwin32 toolkit.
|
---|
768 |
|
---|
769 | =head2 Plan 9
|
---|
770 |
|
---|
771 | See F<README.plan9> in the perl distribution.
|
---|
772 |
|
---|
773 | =head2 QNX
|
---|
774 |
|
---|
775 | See F<README.qnx> in the perl distribution.
|
---|
776 |
|
---|
777 | =head2 AmigaOS
|
---|
778 |
|
---|
779 | See F<README.amigaos> in the perl distribution.
|
---|
780 |
|
---|
781 | =head1 Pragmata
|
---|
782 |
|
---|
783 | Six new pragmatic modules exist:
|
---|
784 |
|
---|
785 | =over 4
|
---|
786 |
|
---|
787 | =item use autouse MODULE => qw(sub1 sub2 sub3)
|
---|
788 |
|
---|
789 | Defers C<require MODULE> until someone calls one of the specified
|
---|
790 | subroutines (which must be exported by MODULE). This pragma should be
|
---|
791 | used with caution, and only when necessary.
|
---|
792 |
|
---|
793 | =item use blib
|
---|
794 |
|
---|
795 | =item use blib 'dir'
|
---|
796 |
|
---|
797 | Looks for MakeMaker-like I<'blib'> directory structure starting in
|
---|
798 | I<dir> (or current directory) and working back up to five levels of
|
---|
799 | parent directories.
|
---|
800 |
|
---|
801 | Intended for use on command line with B<-M> option as a way of testing
|
---|
802 | arbitrary scripts against an uninstalled version of a package.
|
---|
803 |
|
---|
804 | =item use constant NAME => VALUE
|
---|
805 |
|
---|
806 | Provides a convenient interface for creating compile-time constants,
|
---|
807 | See L<perlsub/"Constant Functions">.
|
---|
808 |
|
---|
809 | =item use locale
|
---|
810 |
|
---|
811 | Tells the compiler to enable (or disable) the use of POSIX locales for
|
---|
812 | builtin operations.
|
---|
813 |
|
---|
814 | When C<use locale> is in effect, the current LC_CTYPE locale is used
|
---|
815 | for regular expressions and case mapping; LC_COLLATE for string
|
---|
816 | ordering; and LC_NUMERIC for numeric formatting in printf and sprintf
|
---|
817 | (but B<not> in print). LC_NUMERIC is always used in write, since
|
---|
818 | lexical scoping of formats is problematic at best.
|
---|
819 |
|
---|
820 | Each C<use locale> or C<no locale> affects statements to the end of
|
---|
821 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the
|
---|
822 | current file. Locales can be switched and queried with
|
---|
823 | POSIX::setlocale().
|
---|
824 |
|
---|
825 | See L<perllocale> for more information.
|
---|
826 |
|
---|
827 | =item use ops
|
---|
828 |
|
---|
829 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code.
|
---|
830 |
|
---|
831 | =item use vmsish
|
---|
832 |
|
---|
833 | Enable VMS-specific language features. Currently, there are three
|
---|
834 | VMS-specific features available: 'status', which makes C<$?> and
|
---|
835 | C<system> return genuine VMS status values instead of emulating POSIX;
|
---|
836 | 'exit', which makes C<exit> take a genuine VMS status value instead of
|
---|
837 | assuming that C<exit 1> is an error; and 'time', which makes all times
|
---|
838 | relative to the local time zone, in the VMS tradition.
|
---|
839 |
|
---|
840 | =back
|
---|
841 |
|
---|
842 | =head1 Modules
|
---|
843 |
|
---|
844 | =head2 Required Updates
|
---|
845 |
|
---|
846 | Though Perl 5.004 is compatible with almost all modules that work
|
---|
847 | with Perl 5.003, there are a few exceptions:
|
---|
848 |
|
---|
849 | Module Required Version for Perl 5.004
|
---|
850 | ------ -------------------------------
|
---|
851 | Filter Filter-1.12
|
---|
852 | LWP libwww-perl-5.08
|
---|
853 | Tk Tk400.202 (-w makes noise)
|
---|
854 |
|
---|
855 | Also, the majordomo mailing list program, version 1.94.1, doesn't work
|
---|
856 | with Perl 5.004 (nor with perl 4), because it executes an invalid
|
---|
857 | regular expression. This bug is fixed in majordomo version 1.94.2.
|
---|
858 |
|
---|
859 | =head2 Installation directories
|
---|
860 |
|
---|
861 | The I<installperl> script now places the Perl source files for
|
---|
862 | extensions in the architecture-specific library directory, which is
|
---|
863 | where the shared libraries for extensions have always been. This
|
---|
864 | change is intended to allow administrators to keep the Perl 5.004
|
---|
865 | library directory unchanged from a previous version, without running
|
---|
866 | the risk of binary incompatibility between extensions' Perl source and
|
---|
867 | shared libraries.
|
---|
868 |
|
---|
869 | =head2 Module information summary
|
---|
870 |
|
---|
871 | Brand new modules, arranged by topic rather than strictly
|
---|
872 | alphabetically:
|
---|
873 |
|
---|
874 | CGI.pm Web server interface ("Common Gateway Interface")
|
---|
875 | CGI/Apache.pm Support for Apache's Perl module
|
---|
876 | CGI/Carp.pm Log server errors with helpful context
|
---|
877 | CGI/Fast.pm Support for FastCGI (persistent server process)
|
---|
878 | CGI/Push.pm Support for server push
|
---|
879 | CGI/Switch.pm Simple interface for multiple server types
|
---|
880 |
|
---|
881 | CPAN Interface to Comprehensive Perl Archive Network
|
---|
882 | CPAN::FirstTime Utility for creating CPAN configuration file
|
---|
883 | CPAN::Nox Runs CPAN while avoiding compiled extensions
|
---|
884 |
|
---|
885 | IO.pm Top-level interface to IO::* classes
|
---|
886 | IO/File.pm IO::File extension Perl module
|
---|
887 | IO/Handle.pm IO::Handle extension Perl module
|
---|
888 | IO/Pipe.pm IO::Pipe extension Perl module
|
---|
889 | IO/Seekable.pm IO::Seekable extension Perl module
|
---|
890 | IO/Select.pm IO::Select extension Perl module
|
---|
891 | IO/Socket.pm IO::Socket extension Perl module
|
---|
892 |
|
---|
893 | Opcode.pm Disable named opcodes when compiling Perl code
|
---|
894 |
|
---|
895 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs
|
---|
896 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension
|
---|
897 |
|
---|
898 | FindBin.pm Find path of currently executing program
|
---|
899 |
|
---|
900 | Class/Struct.pm Declare struct-like datatypes as Perl classes
|
---|
901 | File/stat.pm By-name interface to Perl's builtin stat
|
---|
902 | Net/hostent.pm By-name interface to Perl's builtin gethost*
|
---|
903 | Net/netent.pm By-name interface to Perl's builtin getnet*
|
---|
904 | Net/protoent.pm By-name interface to Perl's builtin getproto*
|
---|
905 | Net/servent.pm By-name interface to Perl's builtin getserv*
|
---|
906 | Time/gmtime.pm By-name interface to Perl's builtin gmtime
|
---|
907 | Time/localtime.pm By-name interface to Perl's builtin localtime
|
---|
908 | Time/tm.pm Internal object for Time::{gm,local}time
|
---|
909 | User/grent.pm By-name interface to Perl's builtin getgr*
|
---|
910 | User/pwent.pm By-name interface to Perl's builtin getpw*
|
---|
911 |
|
---|
912 | Tie/RefHash.pm Base class for tied hashes with references as keys
|
---|
913 |
|
---|
914 | UNIVERSAL.pm Base class for *ALL* classes
|
---|
915 |
|
---|
916 | =head2 Fcntl
|
---|
917 |
|
---|
918 | New constants in the existing Fcntl modules are now supported,
|
---|
919 | provided that your operating system happens to support them:
|
---|
920 |
|
---|
921 | F_GETOWN F_SETOWN
|
---|
922 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC
|
---|
923 | O_EXLOCK O_SHLOCK
|
---|
924 |
|
---|
925 | These constants are intended for use with the Perl operators sysopen()
|
---|
926 | and fcntl() and the basic database modules like SDBM_File. For the
|
---|
927 | exact meaning of these and other Fcntl constants please refer to your
|
---|
928 | operating system's documentation for fcntl() and open().
|
---|
929 |
|
---|
930 | In addition, the Fcntl module now provides these constants for use
|
---|
931 | with the Perl operator flock():
|
---|
932 |
|
---|
933 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN
|
---|
934 |
|
---|
935 | These constants are defined in all environments (because where there is
|
---|
936 | no flock() system call, Perl emulates it). However, for historical
|
---|
937 | reasons, these constants are not exported unless they are explicitly
|
---|
938 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>).
|
---|
939 |
|
---|
940 | =head2 IO
|
---|
941 |
|
---|
942 | The IO module provides a simple mechanism to load all the IO modules at one
|
---|
943 | go. Currently this includes:
|
---|
944 |
|
---|
945 | IO::Handle
|
---|
946 | IO::Seekable
|
---|
947 | IO::File
|
---|
948 | IO::Pipe
|
---|
949 | IO::Socket
|
---|
950 |
|
---|
951 | For more information on any of these modules, please see its
|
---|
952 | respective documentation.
|
---|
953 |
|
---|
954 | =head2 Math::Complex
|
---|
955 |
|
---|
956 | The Math::Complex module has been totally rewritten, and now supports
|
---|
957 | more operations. These are overloaded:
|
---|
958 |
|
---|
959 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify)
|
---|
960 |
|
---|
961 | And these functions are now exported:
|
---|
962 |
|
---|
963 | pi i Re Im arg
|
---|
964 | log10 logn ln cbrt root
|
---|
965 | tan
|
---|
966 | csc sec cot
|
---|
967 | asin acos atan
|
---|
968 | acsc asec acot
|
---|
969 | sinh cosh tanh
|
---|
970 | csch sech coth
|
---|
971 | asinh acosh atanh
|
---|
972 | acsch asech acoth
|
---|
973 | cplx cplxe
|
---|
974 |
|
---|
975 | =head2 Math::Trig
|
---|
976 |
|
---|
977 | This new module provides a simpler interface to parts of Math::Complex for
|
---|
978 | those who need trigonometric functions only for real numbers.
|
---|
979 |
|
---|
980 | =head2 DB_File
|
---|
981 |
|
---|
982 | There have been quite a few changes made to DB_File. Here are a few of
|
---|
983 | the highlights:
|
---|
984 |
|
---|
985 | =over 4
|
---|
986 |
|
---|
987 | =item *
|
---|
988 |
|
---|
989 | Fixed a handful of bugs.
|
---|
990 |
|
---|
991 | =item *
|
---|
992 |
|
---|
993 | By public demand, added support for the standard hash function exists().
|
---|
994 |
|
---|
995 | =item *
|
---|
996 |
|
---|
997 | Made it compatible with Berkeley DB 1.86.
|
---|
998 |
|
---|
999 | =item *
|
---|
1000 |
|
---|
1001 | Made negative subscripts work with RECNO interface.
|
---|
1002 |
|
---|
1003 | =item *
|
---|
1004 |
|
---|
1005 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default
|
---|
1006 | mode from 0640 to 0666.
|
---|
1007 |
|
---|
1008 | =item *
|
---|
1009 |
|
---|
1010 | Made DB_File automatically import the open() constants (O_RDWR,
|
---|
1011 | O_CREAT etc.) from Fcntl, if available.
|
---|
1012 |
|
---|
1013 | =item *
|
---|
1014 |
|
---|
1015 | Updated documentation.
|
---|
1016 |
|
---|
1017 | =back
|
---|
1018 |
|
---|
1019 | Refer to the HISTORY section in DB_File.pm for a complete list of
|
---|
1020 | changes. Everything after DB_File 1.01 has been added since 5.003.
|
---|
1021 |
|
---|
1022 | =head2 Net::Ping
|
---|
1023 |
|
---|
1024 | Major rewrite - support added for both udp echo and real icmp pings.
|
---|
1025 |
|
---|
1026 | =head2 Object-oriented overrides for builtin operators
|
---|
1027 |
|
---|
1028 | Many of the Perl builtins returning lists now have
|
---|
1029 | object-oriented overrides. These are:
|
---|
1030 |
|
---|
1031 | File::stat
|
---|
1032 | Net::hostent
|
---|
1033 | Net::netent
|
---|
1034 | Net::protoent
|
---|
1035 | Net::servent
|
---|
1036 | Time::gmtime
|
---|
1037 | Time::localtime
|
---|
1038 | User::grent
|
---|
1039 | User::pwent
|
---|
1040 |
|
---|
1041 | For example, you can now say
|
---|
1042 |
|
---|
1043 | use File::stat;
|
---|
1044 | use User::pwent;
|
---|
1045 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid);
|
---|
1046 |
|
---|
1047 | =head1 Utility Changes
|
---|
1048 |
|
---|
1049 | =head2 pod2html
|
---|
1050 |
|
---|
1051 | =over 4
|
---|
1052 |
|
---|
1053 | =item Sends converted HTML to standard output
|
---|
1054 |
|
---|
1055 | The I<pod2html> utility included with Perl 5.004 is entirely new.
|
---|
1056 | By default, it sends the converted HTML to its standard output,
|
---|
1057 | instead of writing it to a file like Perl 5.003's I<pod2html> did.
|
---|
1058 | Use the B<--outfile=FILENAME> option to write to a file.
|
---|
1059 |
|
---|
1060 | =back
|
---|
1061 |
|
---|
1062 | =head2 xsubpp
|
---|
1063 |
|
---|
1064 | =over 4
|
---|
1065 |
|
---|
1066 | =item C<void> XSUBs now default to returning nothing
|
---|
1067 |
|
---|
1068 | Due to a documentation/implementation bug in previous versions of
|
---|
1069 | Perl, XSUBs with a return type of C<void> have actually been
|
---|
1070 | returning one value. Usually that value was the GV for the XSUB,
|
---|
1071 | but sometimes it was some already freed or reused value, which would
|
---|
1072 | sometimes lead to program failure.
|
---|
1073 |
|
---|
1074 | In Perl 5.004, if an XSUB is declared as returning C<void>, it
|
---|
1075 | actually returns no value, i.e. an empty list (though there is a
|
---|
1076 | backward-compatibility exception; see below). If your XSUB really
|
---|
1077 | does return an SV, you should give it a return type of C<SV *>.
|
---|
1078 |
|
---|
1079 | For backward compatibility, I<xsubpp> tries to guess whether a
|
---|
1080 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>.
|
---|
1081 | It does so by examining the text of the XSUB: if I<xsubpp> finds
|
---|
1082 | what looks like an assignment to C<ST(0)>, it assumes that the
|
---|
1083 | XSUB's return type is really C<SV *>.
|
---|
1084 |
|
---|
1085 | =back
|
---|
1086 |
|
---|
1087 | =head1 C Language API Changes
|
---|
1088 |
|
---|
1089 | =over 4
|
---|
1090 |
|
---|
1091 | =item C<gv_fetchmethod> and C<perl_call_sv>
|
---|
1092 |
|
---|
1093 | The C<gv_fetchmethod> function finds a method for an object, just like
|
---|
1094 | in Perl 5.003. The GV it returns may be a method cache entry.
|
---|
1095 | However, in Perl 5.004, method cache entries are not visible to users;
|
---|
1096 | therefore, they can no longer be passed directly to C<perl_call_sv>.
|
---|
1097 | Instead, you should use the C<GvCV> macro on the GV to extract its CV,
|
---|
1098 | and pass the CV to C<perl_call_sv>.
|
---|
1099 |
|
---|
1100 | The most likely symptom of passing the result of C<gv_fetchmethod> to
|
---|
1101 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called"
|
---|
1102 | error on the I<second> call to a given method (since there is no cache
|
---|
1103 | on the first call).
|
---|
1104 |
|
---|
1105 | =item C<perl_eval_pv>
|
---|
1106 |
|
---|
1107 | A new function handy for eval'ing strings of Perl code inside C code.
|
---|
1108 | This function returns the value from the eval statement, which can
|
---|
1109 | be used instead of fetching globals from the symbol table. See
|
---|
1110 | L<perlguts>, L<perlembed> and L<perlcall> for details and examples.
|
---|
1111 |
|
---|
1112 | =item Extended API for manipulating hashes
|
---|
1113 |
|
---|
1114 | Internal handling of hash keys has changed. The old hashtable API is
|
---|
1115 | still fully supported, and will likely remain so. The additions to the
|
---|
1116 | API allow passing keys as C<SV*>s, so that C<tied> hashes can be given
|
---|
1117 | real scalars as keys rather than plain strings (nontied hashes still
|
---|
1118 | can only use strings as keys). New extensions must use the new hash
|
---|
1119 | access functions and macros if they wish to use C<SV*> keys. These
|
---|
1120 | additions also make it feasible to manipulate C<HE*>s (hash entries),
|
---|
1121 | which can be more efficient. See L<perlguts> for details.
|
---|
1122 |
|
---|
1123 | =back
|
---|
1124 |
|
---|
1125 | =head1 Documentation Changes
|
---|
1126 |
|
---|
1127 | Many of the base and library pods were updated. These
|
---|
1128 | new pods are included in section 1:
|
---|
1129 |
|
---|
1130 | =over 4
|
---|
1131 |
|
---|
1132 | =item L<perldelta>
|
---|
1133 |
|
---|
1134 | This document.
|
---|
1135 |
|
---|
1136 | =item L<perlfaq>
|
---|
1137 |
|
---|
1138 | Frequently asked questions.
|
---|
1139 |
|
---|
1140 | =item L<perllocale>
|
---|
1141 |
|
---|
1142 | Locale support (internationalization and localization).
|
---|
1143 |
|
---|
1144 | =item L<perltoot>
|
---|
1145 |
|
---|
1146 | Tutorial on Perl OO programming.
|
---|
1147 |
|
---|
1148 | =item L<perlapio>
|
---|
1149 |
|
---|
1150 | Perl internal IO abstraction interface.
|
---|
1151 |
|
---|
1152 | =item L<perlmodlib>
|
---|
1153 |
|
---|
1154 | Perl module library and recommended practice for module creation.
|
---|
1155 | Extracted from L<perlmod> (which is much smaller as a result).
|
---|
1156 |
|
---|
1157 | =item L<perldebug>
|
---|
1158 |
|
---|
1159 | Although not new, this has been massively updated.
|
---|
1160 |
|
---|
1161 | =item L<perlsec>
|
---|
1162 |
|
---|
1163 | Although not new, this has been massively updated.
|
---|
1164 |
|
---|
1165 | =back
|
---|
1166 |
|
---|
1167 | =head1 New Diagnostics
|
---|
1168 |
|
---|
1169 | Several new conditions will trigger warnings that were
|
---|
1170 | silent before. Some only affect certain platforms.
|
---|
1171 | The following new warnings and errors outline these.
|
---|
1172 | These messages are classified as follows (listed in
|
---|
1173 | increasing order of desperation):
|
---|
1174 |
|
---|
1175 | (W) A warning (optional).
|
---|
1176 | (D) A deprecation (optional).
|
---|
1177 | (S) A severe warning (mandatory).
|
---|
1178 | (F) A fatal error (trappable).
|
---|
1179 | (P) An internal error you should never see (trappable).
|
---|
1180 | (X) A very fatal error (nontrappable).
|
---|
1181 | (A) An alien error message (not generated by Perl).
|
---|
1182 |
|
---|
1183 | =over 4
|
---|
1184 |
|
---|
1185 | =item "my" variable %s masks earlier declaration in same scope
|
---|
1186 |
|
---|
1187 | (W) A lexical variable has been redeclared in the same scope, effectively
|
---|
1188 | eliminating all access to the previous instance. This is almost always
|
---|
1189 | a typographical error. Note that the earlier variable will still exist
|
---|
1190 | until the end of the scope or until all closure referents to it are
|
---|
1191 | destroyed.
|
---|
1192 |
|
---|
1193 | =item %s argument is not a HASH element or slice
|
---|
1194 |
|
---|
1195 | (F) The argument to delete() must be either a hash element, such as
|
---|
1196 |
|
---|
1197 | $foo{$bar}
|
---|
1198 | $ref->[12]->{"susie"}
|
---|
1199 |
|
---|
1200 | or a hash slice, such as
|
---|
1201 |
|
---|
1202 | @foo{$bar, $baz, $xyzzy}
|
---|
1203 | @{$ref->[12]}{"susie", "queue"}
|
---|
1204 |
|
---|
1205 | =item Allocation too large: %lx
|
---|
1206 |
|
---|
1207 | (X) You can't allocate more than 64K on an MS-DOS machine.
|
---|
1208 |
|
---|
1209 | =item Allocation too large
|
---|
1210 |
|
---|
1211 | (F) You can't allocate more than 2^31+"small amount" bytes.
|
---|
1212 |
|
---|
1213 | =item Applying %s to %s will act on scalar(%s)
|
---|
1214 |
|
---|
1215 | (W) The pattern match (//), substitution (s///), and transliteration (tr///)
|
---|
1216 | operators work on scalar values. If you apply one of them to an array
|
---|
1217 | or a hash, it will convert the array or hash to a scalar value -- the
|
---|
1218 | length of an array, or the population info of a hash -- and then work on
|
---|
1219 | that scalar value. This is probably not what you meant to do. See
|
---|
1220 | L<perlfunc/grep> and L<perlfunc/map> for alternatives.
|
---|
1221 |
|
---|
1222 | =item Attempt to free nonexistent shared string
|
---|
1223 |
|
---|
1224 | (P) Perl maintains a reference counted internal table of strings to
|
---|
1225 | optimize the storage and access of hash keys and other strings. This
|
---|
1226 | indicates someone tried to decrement the reference count of a string
|
---|
1227 | that can no longer be found in the table.
|
---|
1228 |
|
---|
1229 | =item Attempt to use reference as lvalue in substr
|
---|
1230 |
|
---|
1231 | (W) You supplied a reference as the first argument to substr() used
|
---|
1232 | as an lvalue, which is pretty strange. Perhaps you forgot to
|
---|
1233 | dereference it first. See L<perlfunc/substr>.
|
---|
1234 |
|
---|
1235 | =item Bareword "%s" refers to nonexistent package
|
---|
1236 |
|
---|
1237 | (W) You used a qualified bareword of the form C<Foo::>, but
|
---|
1238 | the compiler saw no other uses of that namespace before that point.
|
---|
1239 | Perhaps you need to predeclare a package?
|
---|
1240 |
|
---|
1241 | =item Can't redefine active sort subroutine %s
|
---|
1242 |
|
---|
1243 | (F) Perl optimizes the internal handling of sort subroutines and keeps
|
---|
1244 | pointers into them. You tried to redefine one such sort subroutine when it
|
---|
1245 | was currently active, which is not allowed. If you really want to do
|
---|
1246 | this, you should write C<sort { &func } @x> instead of C<sort func @x>.
|
---|
1247 |
|
---|
1248 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use
|
---|
1249 |
|
---|
1250 | (F) Only hard references are allowed by "strict refs". Symbolic references
|
---|
1251 | are disallowed. See L<perlref>.
|
---|
1252 |
|
---|
1253 | =item Cannot resolve method `%s' overloading `%s' in package `%s'
|
---|
1254 |
|
---|
1255 | (P) Internal error trying to resolve overloading specified by a method
|
---|
1256 | name (as opposed to a subroutine reference).
|
---|
1257 |
|
---|
1258 | =item Constant subroutine %s redefined
|
---|
1259 |
|
---|
1260 | (S) You redefined a subroutine which had previously been eligible for
|
---|
1261 | inlining. See L<perlsub/"Constant Functions"> for commentary and
|
---|
1262 | workarounds.
|
---|
1263 |
|
---|
1264 | =item Constant subroutine %s undefined
|
---|
1265 |
|
---|
1266 | (S) You undefined a subroutine which had previously been eligible for
|
---|
1267 | inlining. See L<perlsub/"Constant Functions"> for commentary and
|
---|
1268 | workarounds.
|
---|
1269 |
|
---|
1270 | =item Copy method did not return a reference
|
---|
1271 |
|
---|
1272 | (F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>.
|
---|
1273 |
|
---|
1274 | =item Died
|
---|
1275 |
|
---|
1276 | (F) You passed die() an empty string (the equivalent of C<die "">) or
|
---|
1277 | you called it with no args and both C<$@> and C<$_> were empty.
|
---|
1278 |
|
---|
1279 | =item Exiting pseudo-block via %s
|
---|
1280 |
|
---|
1281 | (W) You are exiting a rather special block construct (like a sort block or
|
---|
1282 | subroutine) by unconventional means, such as a goto, or a loop control
|
---|
1283 | statement. See L<perlfunc/sort>.
|
---|
1284 |
|
---|
1285 | =item Identifier too long
|
---|
1286 |
|
---|
1287 | (F) Perl limits identifiers (names for variables, functions, etc.) to
|
---|
1288 | 252 characters for simple names, somewhat more for compound names (like
|
---|
1289 | C<$A::B>). You've exceeded Perl's limits. Future versions of Perl are
|
---|
1290 | likely to eliminate these arbitrary limitations.
|
---|
1291 |
|
---|
1292 | =item Illegal character %s (carriage return)
|
---|
1293 |
|
---|
1294 | (F) A carriage return character was found in the input. This is an
|
---|
1295 | error, and not a warning, because carriage return characters can break
|
---|
1296 | multi-line strings, including here documents (e.g., C<print <<EOF;>).
|
---|
1297 |
|
---|
1298 | =item Illegal switch in PERL5OPT: %s
|
---|
1299 |
|
---|
1300 | (X) The PERL5OPT environment variable may only be used to set the
|
---|
1301 | following switches: B<-[DIMUdmw]>.
|
---|
1302 |
|
---|
1303 | =item Integer overflow in hex number
|
---|
1304 |
|
---|
1305 | (S) The literal hex number you have specified is too big for your
|
---|
1306 | architecture. On a 32-bit architecture the largest hex literal is
|
---|
1307 | 0xFFFFFFFF.
|
---|
1308 |
|
---|
1309 | =item Integer overflow in octal number
|
---|
1310 |
|
---|
1311 | (S) The literal octal number you have specified is too big for your
|
---|
1312 | architecture. On a 32-bit architecture the largest octal literal is
|
---|
1313 | 037777777777.
|
---|
1314 |
|
---|
1315 | =item internal error: glob failed
|
---|
1316 |
|
---|
1317 | (P) Something went wrong with the external program(s) used for C<glob>
|
---|
1318 | and C<< <*.c> >>. This may mean that your csh (C shell) is
|
---|
1319 | broken. If so, you should change all of the csh-related variables in
|
---|
1320 | config.sh: If you have tcsh, make the variables refer to it as if it
|
---|
1321 | were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all
|
---|
1322 | empty (except that C<d_csh> should be C<'undef'>) so that Perl will
|
---|
1323 | think csh is missing. In either case, after editing config.sh, run
|
---|
1324 | C<./Configure -S> and rebuild Perl.
|
---|
1325 |
|
---|
1326 | =item Invalid conversion in %s: "%s"
|
---|
1327 |
|
---|
1328 | (W) Perl does not understand the given format conversion.
|
---|
1329 | See L<perlfunc/sprintf>.
|
---|
1330 |
|
---|
1331 | =item Invalid type in pack: '%s'
|
---|
1332 |
|
---|
1333 | (F) The given character is not a valid pack type. See L<perlfunc/pack>.
|
---|
1334 |
|
---|
1335 | =item Invalid type in unpack: '%s'
|
---|
1336 |
|
---|
1337 | (F) The given character is not a valid unpack type. See L<perlfunc/unpack>.
|
---|
1338 |
|
---|
1339 | =item Name "%s::%s" used only once: possible typo
|
---|
1340 |
|
---|
1341 | (W) Typographical errors often show up as unique variable names.
|
---|
1342 | If you had a good reason for having a unique name, then just mention
|
---|
1343 | it again somehow to suppress the message (the C<use vars> pragma is
|
---|
1344 | provided for just this purpose).
|
---|
1345 |
|
---|
1346 | =item Null picture in formline
|
---|
1347 |
|
---|
1348 | (F) The first argument to formline must be a valid format picture
|
---|
1349 | specification. It was found to be empty, which probably means you
|
---|
1350 | supplied it an uninitialized value. See L<perlform>.
|
---|
1351 |
|
---|
1352 | =item Offset outside string
|
---|
1353 |
|
---|
1354 | (F) You tried to do a read/write/send/recv operation with an offset
|
---|
1355 | pointing outside the buffer. This is difficult to imagine.
|
---|
1356 | The sole exception to this is that C<sysread()>ing past the buffer
|
---|
1357 | will extend the buffer and zero pad the new area.
|
---|
1358 |
|
---|
1359 | =item Out of memory!
|
---|
1360 |
|
---|
1361 | (X|F) The malloc() function returned 0, indicating there was insufficient
|
---|
1362 | remaining memory (or virtual memory) to satisfy the request.
|
---|
1363 |
|
---|
1364 | The request was judged to be small, so the possibility to trap it
|
---|
1365 | depends on the way Perl was compiled. By default it is not trappable.
|
---|
1366 | However, if compiled for this, Perl may use the contents of C<$^M> as
|
---|
1367 | an emergency pool after die()ing with this message. In this case the
|
---|
1368 | error is trappable I<once>.
|
---|
1369 |
|
---|
1370 | =item Out of memory during request for %s
|
---|
1371 |
|
---|
1372 | (F) The malloc() function returned 0, indicating there was insufficient
|
---|
1373 | remaining memory (or virtual memory) to satisfy the request. However,
|
---|
1374 | the request was judged large enough (compile-time default is 64K), so
|
---|
1375 | a possibility to shut down by trapping this error is granted.
|
---|
1376 |
|
---|
1377 | =item panic: frexp
|
---|
1378 |
|
---|
1379 | (P) The library function frexp() failed, making printf("%f") impossible.
|
---|
1380 |
|
---|
1381 | =item Possible attempt to put comments in qw() list
|
---|
1382 |
|
---|
1383 | (W) qw() lists contain items separated by whitespace; as with literal
|
---|
1384 | strings, comment characters are not ignored, but are instead treated
|
---|
1385 | as literal data. (You may have used different delimiters than the
|
---|
1386 | parentheses shown here; braces are also frequently used.)
|
---|
1387 |
|
---|
1388 | You probably wrote something like this:
|
---|
1389 |
|
---|
1390 | @list = qw(
|
---|
1391 | a # a comment
|
---|
1392 | b # another comment
|
---|
1393 | );
|
---|
1394 |
|
---|
1395 | when you should have written this:
|
---|
1396 |
|
---|
1397 | @list = qw(
|
---|
1398 | a
|
---|
1399 | b
|
---|
1400 | );
|
---|
1401 |
|
---|
1402 | If you really want comments, build your list the
|
---|
1403 | old-fashioned way, with quotes and commas:
|
---|
1404 |
|
---|
1405 | @list = (
|
---|
1406 | 'a', # a comment
|
---|
1407 | 'b', # another comment
|
---|
1408 | );
|
---|
1409 |
|
---|
1410 | =item Possible attempt to separate words with commas
|
---|
1411 |
|
---|
1412 | (W) qw() lists contain items separated by whitespace; therefore commas
|
---|
1413 | aren't needed to separate the items. (You may have used different
|
---|
1414 | delimiters than the parentheses shown here; braces are also frequently
|
---|
1415 | used.)
|
---|
1416 |
|
---|
1417 | You probably wrote something like this:
|
---|
1418 |
|
---|
1419 | qw! a, b, c !;
|
---|
1420 |
|
---|
1421 | which puts literal commas into some of the list items. Write it without
|
---|
1422 | commas if you don't want them to appear in your data:
|
---|
1423 |
|
---|
1424 | qw! a b c !;
|
---|
1425 |
|
---|
1426 | =item Scalar value @%s{%s} better written as $%s{%s}
|
---|
1427 |
|
---|
1428 | (W) You've used a hash slice (indicated by @) to select a single element of
|
---|
1429 | a hash. Generally it's better to ask for a scalar value (indicated by $).
|
---|
1430 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when
|
---|
1431 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves
|
---|
1432 | like a list when you assign to it, and provides a list context to its
|
---|
1433 | subscript, which can do weird things if you're expecting only one subscript.
|
---|
1434 |
|
---|
1435 | =item Stub found while resolving method `%s' overloading `%s' in %s
|
---|
1436 |
|
---|
1437 | (P) Overloading resolution over @ISA tree may be broken by importing stubs.
|
---|
1438 | Stubs should never be implicitly created, but explicit calls to C<can>
|
---|
1439 | may break this.
|
---|
1440 |
|
---|
1441 | =item Too late for "B<-T>" option
|
---|
1442 |
|
---|
1443 | (X) The #! line (or local equivalent) in a Perl script contains the
|
---|
1444 | B<-T> option, but Perl was not invoked with B<-T> in its argument
|
---|
1445 | list. This is an error because, by the time Perl discovers a B<-T> in
|
---|
1446 | a script, it's too late to properly taint everything from the
|
---|
1447 | environment. So Perl gives up.
|
---|
1448 |
|
---|
1449 | =item untie attempted while %d inner references still exist
|
---|
1450 |
|
---|
1451 | (W) A copy of the object returned from C<tie> (or C<tied>) was still
|
---|
1452 | valid when C<untie> was called.
|
---|
1453 |
|
---|
1454 | =item Unrecognized character %s
|
---|
1455 |
|
---|
1456 | (F) The Perl parser has no idea what to do with the specified character
|
---|
1457 | in your Perl script (or eval). Perhaps you tried to run a compressed
|
---|
1458 | script, a binary program, or a directory as a Perl program.
|
---|
1459 |
|
---|
1460 | =item Unsupported function fork
|
---|
1461 |
|
---|
1462 | (F) Your version of executable does not support forking.
|
---|
1463 |
|
---|
1464 | Note that under some systems, like OS/2, there may be different flavors of
|
---|
1465 | Perl executables, some of which may support fork, some not. Try changing
|
---|
1466 | the name you call Perl by to C<perl_>, C<perl__>, and so on.
|
---|
1467 |
|
---|
1468 | =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
|
---|
1469 |
|
---|
1470 | (D) Perl versions before 5.004 misinterpreted any type marker followed
|
---|
1471 | by "$" and a digit. For example, "$$0" was incorrectly taken to mean
|
---|
1472 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
|
---|
1473 |
|
---|
1474 | However, the developers of Perl 5.004 could not fix this bug completely,
|
---|
1475 | because at least two widely-used modules depend on the old meaning of
|
---|
1476 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
|
---|
1477 | old (broken) way inside strings; but it generates this message as a
|
---|
1478 | warning. And in Perl 5.005, this special treatment will cease.
|
---|
1479 |
|
---|
1480 | =item Value of %s can be "0"; test with defined()
|
---|
1481 |
|
---|
1482 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>,
|
---|
1483 | or C<readdir()> as a boolean value. Each of these constructs can return a
|
---|
1484 | value of "0"; that would make the conditional expression false, which is
|
---|
1485 | probably not what you intended. When using these constructs in conditional
|
---|
1486 | expressions, test their values with the C<defined> operator.
|
---|
1487 |
|
---|
1488 | =item Variable "%s" may be unavailable
|
---|
1489 |
|
---|
1490 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named>
|
---|
1491 | subroutine, and outside that is another subroutine; and the anonymous
|
---|
1492 | (innermost) subroutine is referencing a lexical variable defined in
|
---|
1493 | the outermost subroutine. For example:
|
---|
1494 |
|
---|
1495 | sub outermost { my $a; sub middle { sub { $a } } }
|
---|
1496 |
|
---|
1497 | If the anonymous subroutine is called or referenced (directly or
|
---|
1498 | indirectly) from the outermost subroutine, it will share the variable
|
---|
1499 | as you would expect. But if the anonymous subroutine is called or
|
---|
1500 | referenced when the outermost subroutine is not active, it will see
|
---|
1501 | the value of the shared variable as it was before and during the
|
---|
1502 | *first* call to the outermost subroutine, which is probably not what
|
---|
1503 | you want.
|
---|
1504 |
|
---|
1505 | In these circumstances, it is usually best to make the middle
|
---|
1506 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific
|
---|
1507 | support for shared variables in nested anonymous subroutines; a named
|
---|
1508 | subroutine in between interferes with this feature.
|
---|
1509 |
|
---|
1510 | =item Variable "%s" will not stay shared
|
---|
1511 |
|
---|
1512 | (W) An inner (nested) I<named> subroutine is referencing a lexical
|
---|
1513 | variable defined in an outer subroutine.
|
---|
1514 |
|
---|
1515 | When the inner subroutine is called, it will probably see the value of
|
---|
1516 | the outer subroutine's variable as it was before and during the
|
---|
1517 | *first* call to the outer subroutine; in this case, after the first
|
---|
1518 | call to the outer subroutine is complete, the inner and outer
|
---|
1519 | subroutines will no longer share a common value for the variable. In
|
---|
1520 | other words, the variable will no longer be shared.
|
---|
1521 |
|
---|
1522 | Furthermore, if the outer subroutine is anonymous and references a
|
---|
1523 | lexical variable outside itself, then the outer and inner subroutines
|
---|
1524 | will I<never> share the given variable.
|
---|
1525 |
|
---|
1526 | This problem can usually be solved by making the inner subroutine
|
---|
1527 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that
|
---|
1528 | reference variables in outer subroutines are called or referenced,
|
---|
1529 | they are automatically rebound to the current values of such
|
---|
1530 | variables.
|
---|
1531 |
|
---|
1532 | =item Warning: something's wrong
|
---|
1533 |
|
---|
1534 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or
|
---|
1535 | you called it with no args and C<$_> was empty.
|
---|
1536 |
|
---|
1537 | =item Ill-formed logical name |%s| in prime_env_iter
|
---|
1538 |
|
---|
1539 | (W) A warning peculiar to VMS. A logical name was encountered when preparing
|
---|
1540 | to iterate over %ENV which violates the syntactic rules governing logical
|
---|
1541 | names. Since it cannot be translated normally, it is skipped, and will not
|
---|
1542 | appear in %ENV. This may be a benign occurrence, as some software packages
|
---|
1543 | might directly modify logical name tables and introduce nonstandard names,
|
---|
1544 | or it may indicate that a logical name table has been corrupted.
|
---|
1545 |
|
---|
1546 | =item Got an error from DosAllocMem
|
---|
1547 |
|
---|
1548 | (P) An error peculiar to OS/2. Most probably you're using an obsolete
|
---|
1549 | version of Perl, and this should not happen anyway.
|
---|
1550 |
|
---|
1551 | =item Malformed PERLLIB_PREFIX
|
---|
1552 |
|
---|
1553 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form
|
---|
1554 |
|
---|
1555 | prefix1;prefix2
|
---|
1556 |
|
---|
1557 | or
|
---|
1558 |
|
---|
1559 | prefix1 prefix2
|
---|
1560 |
|
---|
1561 | with nonempty prefix1 and prefix2. If C<prefix1> is indeed a prefix
|
---|
1562 | of a builtin library search path, prefix2 is substituted. The error
|
---|
1563 | may appear if components are not found, or are too long. See
|
---|
1564 | "PERLLIB_PREFIX" in F<README.os2>.
|
---|
1565 |
|
---|
1566 | =item PERL_SH_DIR too long
|
---|
1567 |
|
---|
1568 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the
|
---|
1569 | C<sh>-shell in. See "PERL_SH_DIR" in F<README.os2>.
|
---|
1570 |
|
---|
1571 | =item Process terminated by SIG%s
|
---|
1572 |
|
---|
1573 | (W) This is a standard message issued by OS/2 applications, while *nix
|
---|
1574 | applications die in silence. It is considered a feature of the OS/2
|
---|
1575 | port. One can easily disable this by appropriate sighandlers, see
|
---|
1576 | L<perlipc/"Signals">. See also "Process terminated by SIGTERM/SIGINT"
|
---|
1577 | in F<README.os2>.
|
---|
1578 |
|
---|
1579 | =back
|
---|
1580 |
|
---|
1581 | =head1 BUGS
|
---|
1582 |
|
---|
1583 | If you find what you think is a bug, you might check the headers of
|
---|
1584 | recently posted articles in the comp.lang.perl.misc newsgroup.
|
---|
1585 | There may also be information at http://www.perl.com/perl/ , the Perl
|
---|
1586 | Home Page.
|
---|
1587 |
|
---|
1588 | If you believe you have an unreported bug, please run the B<perlbug>
|
---|
1589 | program included with your release. Make sure you trim your bug down
|
---|
1590 | to a tiny but sufficient test case. Your bug report, along with the
|
---|
1591 | output of C<perl -V>, will be sent off to <F<[email protected]>> to be
|
---|
1592 | analysed by the Perl porting team.
|
---|
1593 |
|
---|
1594 | =head1 SEE ALSO
|
---|
1595 |
|
---|
1596 | The F<Changes> file for exhaustive details on what changed.
|
---|
1597 |
|
---|
1598 | The F<INSTALL> file for how to build Perl. This file has been
|
---|
1599 | significantly updated for 5.004, so even veteran users should
|
---|
1600 | look through it.
|
---|
1601 |
|
---|
1602 | The F<README> file for general stuff.
|
---|
1603 |
|
---|
1604 | The F<Copying> file for copyright information.
|
---|
1605 |
|
---|
1606 | =head1 HISTORY
|
---|
1607 |
|
---|
1608 | Constructed by Tom Christiansen, grabbing material with permission
|
---|
1609 | from innumerable contributors, with kibitzing by more than a few Perl
|
---|
1610 | porters.
|
---|
1611 |
|
---|
1612 | Last update: Wed May 14 11:14:09 EDT 1997
|
---|