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1 | =head1 NAME |
2 | |
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3 | perldelta - what's new for perl5.004 |
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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 | |
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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. |
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16 | |
17 | =head1 Core Changes |
18 | |
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19 | Most importantly, many bugs were fixed, including several security |
20 | problems. See the F<Changes> file in the distribution for details. |
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21 | |
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22 | =head2 Compilation option: Binary compatibility with 5.003 |
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23 | |
24 | There is a new Configure question that asks if you want to maintain |
25 | binary compatibility with Perl 5.003. If you choose binary |
26 | compatibility, you do not have to recompile your extensions, but you |
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27 | might have symbol conflicts if you embed Perl in another application, |
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28 | just as in the 5.003 release. By default, binary compatibility |
29 | is preserved at the expense of symbol table pollution. |
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30 | |
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31 | =head2 $PERL5OPT environment variable |
32 | |
33 | You may now put Perl options in the $PERL5OPT environment variable. |
34 | Unless Perl is running with taint checks, it will interpret this |
35 | variable as if its contents had appeared on a "#!perl" line at the |
36 | beginning of your script, except that hyphens are optional. PERL5OPT |
37 | may only be used to set the following switches: B<-[DIMUdmw]>. |
38 | |
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39 | =head2 Limitations on B<-M>, B<-m>, and B<-T> options |
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40 | |
41 | The C<-M> and C<-m> options are no longer allowed on the C<#!> line of |
42 | a script. If a script needs a module, it should invoke it with the |
43 | C<use> pragma. |
44 | |
45 | The B<-T> option is also forbidden on the C<#!> line of a script, |
46 | unless it was present on the Perl command line. Due to the way C<#!> |
47 | works, this usually means that B<-T> must be in the first argument. |
48 | Thus: |
49 | |
50 | #!/usr/bin/perl -T -w |
51 | |
52 | will probably work for an executable script invoked as C<scriptname>, |
53 | while: |
54 | |
55 | #!/usr/bin/perl -w -T |
56 | |
57 | will probably fail under the same conditions. (Non-Unix systems will |
58 | probably not follow this rule.) But C<perl scriptname> is guaranteed |
59 | to fail, since then there is no chance of B<-T> being found on the |
60 | command line before it is found on the C<#!> line. |
61 | |
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62 | =head2 More precise warnings |
63 | |
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64 | If you removed the B<-w> option from your Perl 5.003 scripts because it |
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65 | made Perl too verbose, we recommend that you try putting it back when |
66 | you upgrade to Perl 5.004. Each new perl version tends to remove some |
67 | undesirable warnings, while adding new warnings that may catch bugs in |
68 | your scripts. |
69 | |
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70 | =head2 Deprecated: Inherited C<AUTOLOAD> for non-methods |
71 | |
72 | Before Perl 5.004, C<AUTOLOAD> functions were looked up as methods |
73 | (using the C<@ISA> hierarchy), even when the function to be autoloaded |
74 | was called as a plain function (e.g. C<Foo::bar()>), not a method |
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75 | (e.g. C<Foo-E<gt>bar()> or C<$obj-E<gt>bar()>). |
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76 | |
77 | Perl 5.005 will use method lookup only for methods' C<AUTOLOAD>s. |
78 | However, there is a significant base of existing code that may be using |
79 | the old behavior. So, as an interim step, Perl 5.004 issues an optional |
80 | warning when a non-method uses an inherited C<AUTOLOAD>. |
81 | |
82 | The simple rule is: Inheritance will not work when autoloading |
83 | non-methods. The simple fix for old code is: In any module that used to |
84 | depend on inheriting C<AUTOLOAD> for non-methods from a base class named |
85 | C<BaseClass>, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup. |
86 | |
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87 | =head2 Subroutine arguments created only when they're modified |
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88 | |
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89 | In Perl 5.004, nonexistent array and hash elements used as subroutine |
90 | parameters are brought into existence only if they are actually |
91 | assigned to (via C<@_>). |
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92 | |
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93 | Earlier versions of Perl vary in their handling of such arguments. |
94 | Perl versions 5.002 and 5.003 always brought them into existence. |
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95 | Perl versions 5.000 and 5.001 brought them into existence only if |
96 | they were not the first argument (which was almost certainly a bug). |
97 | Earlier versions of Perl never brought them into existence. |
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98 | |
99 | For example, given this code: |
100 | |
101 | undef @a; undef %a; |
102 | sub show { print $_[0] }; |
103 | sub change { $_[0]++ }; |
104 | show($a[2]); |
105 | change($a{b}); |
106 | |
107 | After this code executes in Perl 5.004, $a{b} exists but $a[2] does |
108 | not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed |
109 | (but $a[2]'s value would have been undefined). |
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110 | |
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111 | =head2 Group vector changeable with C<$)> |
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112 | |
113 | The C<$)> special variable has always (well, in Perl 5, at least) |
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114 | reflected not only the current effective group, but also the group list |
115 | as returned by the C<getgroups()> C function (if there is one). |
116 | However, until this release, there has not been a way to call the |
117 | C<setgroups()> C function from Perl. |
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118 | |
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119 | In Perl 5.004, assigning to C<$)> is exactly symmetrical with examining |
120 | it: The first number in its string value is used as the effective gid; |
121 | if there are any numbers after the first one, they are passed to the |
122 | C<setgroups()> C function (if there is one). |
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123 | |
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124 | =head2 Fixed parsing of $$<digit>, &$<digit>, etc. |
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125 | |
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126 | Perl versions before 5.004 misinterpreted any type marker followed by |
127 | "$" and a digit. For example, "$$0" was incorrectly taken to mean |
128 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
129 | |
130 | However, the developers of Perl 5.004 could not fix this bug completely, |
131 | because at least two widely-used modules depend on the old meaning of |
132 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
133 | old (broken) way inside strings; but it generates this message as a |
134 | warning. And in Perl 5.005, this special treatment will cease. |
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135 | |
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136 | =head2 No resetting of $. on implicit close |
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137 | |
138 | The documentation for Perl 5.0 has always stated that C<$.> is I<not> |
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139 | reset when an already-open file handle is reopened with no intervening |
140 | call to C<close>. Due to a bug, perl versions 5.000 through 5.003 |
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141 | I<did> reset C<$.> under that circumstance; Perl 5.004 does not. |
142 | |
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143 | =head2 C<wantarray> may return undef |
144 | |
145 | The C<wantarray> operator returns true if a subroutine is expected to |
146 | return a list, and false otherwise. In Perl 5.004, C<wantarray> can |
147 | also return the undefined value if a subroutine's return value will |
148 | not be used at all, which allows subroutines to avoid a time-consuming |
149 | calculation of a return value if it isn't going to be used. |
150 | |
151 | =head2 Changes to tainting checks |
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152 | |
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153 | A bug in previous versions may have failed to detect some insecure |
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154 | conditions when taint checks are turned on. (Taint checks are used |
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155 | in setuid or setgid scripts, or when explicitly turned on with the |
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156 | C<-T> invocation option.) Although it's unlikely, this may cause a |
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157 | previously-working script to now fail -- which should be construed |
158 | as a blessing, since that indicates a potentially-serious security |
159 | hole was just plugged. |
160 | |
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161 | The new restrictions when tainting include: |
162 | |
163 | =over |
164 | |
165 | =item No glob() or <*> |
166 | |
167 | These operators may spawn the C shell (csh), which cannot be made |
168 | safe. This restriction will be lifted in a future version of Perl |
169 | when globbing is implemented without the use of an external program. |
170 | |
171 | =item No spawning if tainted $CDPATH, $ENV, $BASH_ENV |
172 | |
173 | These environment variables may alter the behavior of spawned programs |
174 | (especially shells) in ways that subvert security. So now they are |
175 | treated as dangerous, in the manner of $IFS and $PATH. |
176 | |
177 | =item No spawning if tainted $TERM doesn't look like a terminal name |
178 | |
179 | Some termcap libraries do unsafe things with $TERM. However, it would be |
180 | unnecessarily harsh to treat all $TERM values as unsafe, since only shell |
181 | metacharacters can cause trouble in $TERM. So a tainted $TERM is |
182 | considered to be safe if it contains only alphanumerics, underscores, |
183 | dashes, and colons, and unsafe if it contains other characters (including |
184 | whitespace). |
185 | |
186 | =back |
187 | |
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188 | =head2 New Opcode module and revised Safe module |
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189 | |
190 | A new Opcode module supports the creation, manipulation and |
191 | application of opcode masks. The revised Safe module has a new API |
192 | and is implemented using the new Opcode module. Please read the new |
193 | Opcode and Safe documentation. |
194 | |
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195 | =head2 Embedding improvements |
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196 | |
197 | In older versions of Perl it was not possible to create more than one |
198 | Perl interpreter instance inside a single process without leaking like a |
199 | sieve and/or crashing. The bugs that caused this behavior have all been |
200 | fixed. However, you still must take care when embedding Perl in a C |
201 | program. See the updated perlembed manpage for tips on how to manage |
202 | your interpreters. |
203 | |
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204 | =head2 Internal change: FileHandle class based on IO::* classes |
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205 | |
206 | File handles are now stored internally as type IO::Handle. The |
207 | FileHandle module is still supported for backwards compatibility, but |
208 | it is now merely a front end to the IO::* modules -- specifically, |
209 | IO::Handle, IO::Seekable, and IO::File. We suggest, but do not |
210 | require, that you use the IO::* modules in new code. |
211 | |
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212 | In harmony with this change, C<*GLOB{FILEHANDLE}> is now just a |
213 | backward-compatible synonym for C<*GLOB{IO}>. |
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214 | |
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215 | =head2 Internal change: PerlIO abstraction interface |
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216 | |
217 | It is now possible to build Perl with AT&T's sfio IO package |
218 | instead of stdio. See L<perlapio> for more details, and |
219 | the F<INSTALL> file for how to use it. |
220 | |
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221 | =head2 New and changed syntax |
222 | |
223 | =over |
224 | |
225 | =item $coderef->(PARAMS) |
226 | |
227 | A subroutine reference may now be suffixed with an arrow and a |
228 | (possibly empty) parameter list. This syntax denotes a call of the |
229 | referenced subroutine, with the given parameters (if any). |
230 | |
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231 | This new syntax follows the pattern of S<C<$hashref-E<gt>{FOO}>> and |
232 | S<C<$aryref-E<gt>[$foo]>>: You may now write S<C<&$subref($foo)>> as |
233 | S<C<$subref-E<gt>($foo)>>. All of these arrow terms may be chained; |
234 | thus, S<C<&{$table-E<gt>{FOO}}($bar)>> may now be written |
235 | S<C<$table-E<gt>{FOO}-E<gt>($bar)>>. |
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236 | |
237 | =back |
238 | |
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239 | =head2 New and changed builtin constants |
240 | |
241 | =over |
242 | |
243 | =item __PACKAGE__ |
244 | |
245 | The current package name at compile time, or the undefined value if |
246 | there is no current package (due to a C<package;> directive). Like |
247 | C<__FILE__> and C<__LINE__>, C<__PACKAGE__> does I<not> interpolate |
248 | into strings. |
249 | |
250 | =back |
251 | |
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252 | =head2 New and changed builtin variables |
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253 | |
254 | =over |
255 | |
256 | =item $^E |
257 | |
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258 | Extended error message on some platforms. (Also known as |
259 | $EXTENDED_OS_ERROR if you C<use English>). |
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260 | |
261 | =item $^H |
262 | |
263 | The current set of syntax checks enabled by C<use strict>. See the |
264 | documentation of C<strict> for more details. Not actually new, but |
265 | newly documented. |
266 | Because it is intended for internal use by Perl core components, |
267 | there is no C<use English> long name for this variable. |
268 | |
269 | =item $^M |
270 | |
271 | By default, running out of memory it is not trappable. However, if |
272 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
273 | pool after die()ing with this message. Suppose that your Perl were |
274 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
275 | |
276 | $^M = 'a' x (1<<16); |
277 | |
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278 | would allocate a 64K buffer for use when in emergency. |
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279 | See the F<INSTALL> file for information on how to enable this option. |
280 | As a disincentive to casual use of this advanced feature, |
281 | there is no C<use English> long name for this variable. |
282 | |
283 | =back |
284 | |
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285 | =head2 New and changed builtin functions |
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286 | |
287 | =over |
288 | |
289 | =item delete on slices |
290 | |
291 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
292 | |
293 | =item flock |
294 | |
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295 | is now supported on more platforms, prefers fcntl to lockf when |
296 | emulating, and always flushes before (un)locking. |
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297 | |
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298 | =item printf and sprintf |
299 | |
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300 | Perl now implements these functions itself; it doesn't use the C |
301 | library function sprintf() any more, except for floating-point |
302 | numbers, and even then only known flags are allowed. As a result, it |
303 | is now possible to know which conversions and flags will work, and |
304 | what they will do. |
305 | |
306 | The new conversions in Perl's sprintf() are: |
307 | |
308 | %i a synonym for %d |
309 | %p a pointer (the address of the Perl value, in hexadecimal) |
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310 | %n special: *stores* the number of characters output so far |
311 | into the next variable in the parameter list |
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312 | |
313 | The new flags that go between the C<%> and the conversion are: |
314 | |
315 | # prefix octal with "0", hex with "0x" |
316 | h interpret integer as C type "short" or "unsigned short" |
317 | V interpret integer as Perl's standard integer type |
318 | |
319 | Also, where a number would appear in the flags, an asterisk ("*") may |
320 | be used instead, in which case Perl uses the next item in the |
321 | parameter list as the given number (that is, as the field width or |
322 | precision). If a field width obtained through "*" is negative, it has |
323 | the same effect as the '-' flag: left-justification. |
324 | |
325 | See L<perlfunc/sprintf> for a complete list of conversion and flags. |
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326 | |
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327 | =item keys as an lvalue |
328 | |
329 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
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330 | allocated for the given hash. This can gain you a measure of efficiency if |
331 | you know the hash is going to get big. (This is similar to pre-extending |
332 | an array by assigning a larger number to $#array.) If you say |
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333 | |
334 | keys %hash = 200; |
335 | |
336 | then C<%hash> will have at least 200 buckets allocated for it. These |
337 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
338 | %hash> if you want to free the storage while C<%hash> is still in scope. |
339 | You can't shrink the number of buckets allocated for the hash using |
340 | C<keys> in this way (but you needn't worry about doing this by accident, |
341 | as trying has no effect). |
342 | |
343 | =item my() in Control Structures |
344 | |
345 | You can now use my() (with or without the parentheses) in the control |
346 | expressions of control structures such as: |
347 | |
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348 | while (defined(my $line = <>)) { |
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349 | $line = lc $line; |
350 | } continue { |
351 | print $line; |
352 | } |
353 | |
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354 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
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355 | user_agrees(); |
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356 | } elsif ($answer =~ /^n(o)?$/i) { |
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357 | user_disagrees(); |
358 | } else { |
359 | chomp $answer; |
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360 | die "`$answer' is neither `yes' nor `no'"; |
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361 | } |
362 | |
363 | Also, you can declare a foreach loop control variable as lexical by |
364 | preceding it with the word "my". For example, in: |
365 | |
366 | foreach my $i (1, 2, 3) { |
367 | some_function(); |
368 | } |
369 | |
370 | $i is a lexical variable, and the scope of $i extends to the end of |
371 | the loop, but not beyond it. |
372 | |
373 | Note that you still cannot use my() on global punctuation variables |
374 | such as $_ and the like. |
375 | |
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376 | =item pack() and unpack() |
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377 | |
378 | A new format 'w' represents a BER compressed integer (as defined in |
379 | ASN.1). Its format is a sequence of one or more bytes, each of which |
380 | provides seven bits of the total value, with the most significant |
381 | first. Bit eight of each byte is set, except for the last byte, in |
382 | which bit eight is clear. |
383 | |
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384 | Both pack() and unpack() now fail when their templates contain invalid |
385 | types. (Invalid types used to be ignored.) |
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386 | |
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387 | =item sysseek() |
388 | |
389 | The new sysseek() operator is a variant of seek() that sets and gets the |
390 | file's system read/write position, using the lseek(2) system call. It is |
391 | the only reliable way to seek before using sysread() or syswrite(). Its |
392 | return value is the new position, or the undefined value on failure. |
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393 | |
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394 | =item use VERSION |
395 | |
396 | If the first argument to C<use> is a number, it is treated as a version |
397 | number instead of a module name. If the version of the Perl interpreter |
398 | is less than VERSION, then an error message is printed and Perl exits |
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399 | immediately. Because C<use> occurs at compile time, this check happens |
400 | immediately during the compilation process, unlike C<require VERSION>, |
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401 | which waits until runtime for the check. This is often useful if you |
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402 | need to check the current Perl version before C<use>ing library modules |
403 | which have changed in incompatible ways from older versions of Perl. |
404 | (We try not to do this more than we have to.) |
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405 | |
406 | =item use Module VERSION LIST |
407 | |
408 | If the VERSION argument is present between Module and LIST, then the |
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409 | C<use> will call the VERSION method in class Module with the given |
410 | version as an argument. The default VERSION method, inherited from |
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411 | the UNIVERSAL class, croaks if the given version is larger than the |
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412 | value of the variable $Module::VERSION. (Note that there is not a |
413 | comma after VERSION!) |
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414 | |
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415 | This version-checking mechanism is similar to the one currently used |
416 | in the Exporter module, but it is faster and can be used with modules |
417 | that don't use the Exporter. It is the recommended method for new |
418 | code. |
419 | |
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420 | =item prototype(FUNCTION) |
421 | |
422 | Returns the prototype of a function as a string (or C<undef> if the |
423 | function has no prototype). FUNCTION is a reference to or the name of the |
424 | function whose prototype you want to retrieve. |
425 | (Not actually new; just never documented before.) |
426 | |
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427 | =item srand |
428 | |
429 | The default seed for C<srand>, which used to be C<time>, has been changed. |
430 | Now it's a heady mix of difficult-to-predict system-dependent values, |
431 | which should be sufficient for most everyday purposes. |
432 | |
433 | Previous to version 5.004, calling C<rand> without first calling C<srand> |
434 | would yield the same sequence of random numbers on most or all machines. |
435 | Now, when perl sees that you're calling C<rand> and haven't yet called |
436 | C<srand>, it calls C<srand> with the default seed. You should still call |
437 | C<srand> manually if your code might ever be run on a pre-5.004 system, |
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438 | of course, or if you want a seed other than the default. |
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439 | |
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440 | =item $_ as Default |
441 | |
442 | Functions documented in the Camel to default to $_ now in |
443 | fact do, and all those that do are so documented in L<perlfunc>. |
444 | |
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445 | =item C<m//gc> does not reset search position on failure |
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446 | |
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447 | The C<m//g> match iteration construct has always reset its target |
448 | string's search position (which is visible through the C<pos> operator) |
449 | when a match fails; as a result, the next C<m//g> match after a failure |
450 | starts again at the beginning of the string. With Perl 5.004, this |
451 | reset may be disabled by adding the "c" (for "continue") modifier, |
452 | i.e. C<m//gc>. This feature, in conjunction with the C<\G> zero-width |
453 | assertion, makes it possible to chain matches together. See L<perlop> |
454 | and L<perlre>. |
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455 | |
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456 | =item C<m//x> ignores whitespace before ?*+{} |
457 | |
458 | The C<m//x> construct has always been intended to ignore all unescaped |
459 | whitespace. However, before Perl 5.004, whitespace had the effect of |
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460 | escaping repeat modifiers like "*" or "?"; for example, C</a *b/x> was |
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461 | (mis)interpreted as C</a\*b/x>. This bug has been fixed in 5.004. |
462 | |
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463 | =item nested C<sub{}> closures work now |
464 | |
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465 | Prior to the 5.004 release, nested anonymous functions didn't work |
466 | right. They do now. |
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467 | |
468 | =item formats work right on changing lexicals |
469 | |
470 | Just like anonymous functions that contain lexical variables |
471 | that change (like a lexical index variable for a C<foreach> loop), |
472 | formats now work properly. For example, this silently failed |
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473 | before (printed only zeros), but is fine now: |
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474 | |
475 | my $i; |
476 | foreach $i ( 1 .. 10 ) { |
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477 | write; |
478 | } |
479 | format = |
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480 | my i is @# |
481 | $i |
482 | . |
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483 | |
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484 | =back |
485 | |
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486 | =head2 New builtin methods |
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487 | |
488 | The C<UNIVERSAL> package automatically contains the following methods that |
489 | are inherited by all other classes: |
490 | |
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491 | =over |
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492 | |
493 | =item isa(CLASS) |
494 | |
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495 | C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS> |
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496 | |
497 | C<isa> is also exportable and can be called as a sub with two arguments. This |
498 | allows the ability to check what a reference points to. Example: |
499 | |
500 | use UNIVERSAL qw(isa); |
501 | |
502 | if(isa($ref, 'ARRAY')) { |
503 | ... |
504 | } |
505 | |
506 | =item can(METHOD) |
507 | |
508 | C<can> checks to see if its object has a method called C<METHOD>, |
509 | if it does then a reference to the sub is returned; if it does not then |
510 | I<undef> is returned. |
511 | |
512 | =item VERSION( [NEED] ) |
513 | |
71be2cbc |
514 | C<VERSION> returns the version number of the class (package). If the |
515 | NEED argument is given then it will check that the current version (as |
516 | defined by the $VERSION variable in the given package) not less than |
517 | NEED; it will die if this is not the case. This method is normally |
518 | called as a class method. This method is called automatically by the |
519 | C<VERSION> form of C<use>. |
5f05dabc |
520 | |
521 | use A 1.2 qw(some imported subs); |
71be2cbc |
522 | # implies: |
523 | A->VERSION(1.2); |
5f05dabc |
524 | |
5f05dabc |
525 | =back |
526 | |
527 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
774d564b |
528 | C<isa> uses a very similar method and caching strategy. This may cause |
5f05dabc |
529 | strange effects if the Perl code dynamically changes @ISA in any package. |
530 | |
531 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
532 | You do not need to C<use UNIVERSAL> in order to make these methods |
533 | available to your program. This is necessary only if you wish to |
534 | have C<isa> available as a plain subroutine in the current package. |
535 | |
54310121 |
536 | =head2 TIEHANDLE now supported |
5f05dabc |
537 | |
774d564b |
538 | See L<perltie> for other kinds of tie()s. |
539 | |
5f05dabc |
540 | =over |
541 | |
542 | =item TIEHANDLE classname, LIST |
543 | |
544 | This is the constructor for the class. That means it is expected to |
545 | return an object of some sort. The reference can be used to |
546 | hold some internal information. |
547 | |
2ae324a7 |
548 | sub TIEHANDLE { |
549 | print "<shout>\n"; |
550 | my $i; |
774d564b |
551 | return bless \$i, shift; |
552 | } |
5f05dabc |
553 | |
554 | =item PRINT this, LIST |
555 | |
556 | This method will be triggered every time the tied handle is printed to. |
557 | Beyond its self reference it also expects the list that was passed to |
558 | the print function. |
559 | |
2ae324a7 |
560 | sub PRINT { |
561 | $r = shift; |
562 | $$r++; |
774d564b |
563 | return print join( $, => map {uc} @_), $\; |
564 | } |
5f05dabc |
565 | |
46fc3d4c |
566 | =item PRINTF this, LIST |
567 | |
568 | This method will be triggered every time the tied handle is printed to |
569 | with the C<printf()> function. |
570 | Beyond its self reference it also expects the format and list that was |
571 | passed to the printf function. |
572 | |
573 | sub PRINTF { |
574 | shift; |
575 | my $fmt = shift; |
576 | print sprintf($fmt, @_)."\n"; |
577 | } |
578 | |
2ae324a7 |
579 | =item READ this LIST |
580 | |
581 | This method will be called when the handle is read from via the C<read> |
582 | or C<sysread> functions. |
583 | |
584 | sub READ { |
585 | $r = shift; |
586 | my($buf,$len,$offset) = @_; |
587 | print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset"; |
588 | } |
589 | |
5f05dabc |
590 | =item READLINE this |
591 | |
592 | This method will be called when the handle is read from. The method |
593 | should return undef when there is no more data. |
594 | |
2ae324a7 |
595 | sub READLINE { |
596 | $r = shift; |
597 | return "PRINT called $$r times\n" |
774d564b |
598 | } |
5f05dabc |
599 | |
2ae324a7 |
600 | =item GETC this |
601 | |
602 | This method will be called when the C<getc> function is called. |
603 | |
604 | sub GETC { print "Don't GETC, Get Perl"; return "a"; } |
605 | |
5f05dabc |
606 | =item DESTROY this |
607 | |
608 | As with the other types of ties, this method will be called when the |
609 | tied handle is about to be destroyed. This is useful for debugging and |
610 | possibly for cleaning up. |
611 | |
2ae324a7 |
612 | sub DESTROY { |
774d564b |
613 | print "</shout>\n"; |
614 | } |
5f05dabc |
615 | |
616 | =back |
617 | |
54310121 |
618 | =head2 Malloc enhancements |
aa689395 |
619 | |
2ae324a7 |
620 | Four new compilation flags are recognized by malloc.c. (They have no |
621 | effect if perl is compiled with system malloc().) |
622 | |
623 | =over |
624 | |
625 | =item -DDEBUGGING_MSTATS |
626 | |
627 | If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print |
628 | memory statistics at runtime by running Perl thusly: |
aa689395 |
629 | |
630 | env PERL_DEBUG_MSTATS=2 perl your_script_here |
631 | |
632 | The value of 2 means to print statistics after compilation and on |
633 | exit; with a value of 1, the statistics ares printed only on exit. |
634 | (If you want the statistics at an arbitrary time, you'll need to |
635 | install the optional module Devel::Peek.) |
636 | |
aa689395 |
637 | =item -DEMERGENCY_SBRK |
638 | |
639 | If this macro is defined, running out of memory need not be a fatal |
640 | error: a memory pool can allocated by assigning to the special |
641 | variable C<$^M>. See L<"$^M">. |
774d564b |
642 | |
aa689395 |
643 | =item -DPACK_MALLOC |
644 | |
645 | Perl memory allocation is by bucket with sizes close to powers of two. |
646 | Because of these malloc overhead may be big, especially for data of |
647 | size exactly a power of two. If C<PACK_MALLOC> is defined, perl uses |
648 | a slightly different algorithm for small allocations (up to 64 bytes |
649 | long), which makes it possible to have overhead down to 1 byte for |
650 | allocations which are powers of two (and appear quite often). |
651 | |
652 | Expected memory savings (with 8-byte alignment in C<alignbytes>) is |
653 | about 20% for typical Perl usage. Expected slowdown due to additional |
654 | malloc overhead is in fractions of a percent (hard to measure, because |
655 | of the effect of saved memory on speed). |
656 | |
657 | =item -DTWO_POT_OPTIMIZE |
658 | |
659 | Similarly to C<PACK_MALLOC>, this macro improves allocations of data |
660 | with size close to a power of two; but this works for big allocations |
661 | (starting with 16K by default). Such allocations are typical for big |
662 | hashes and special-purpose scripts, especially image processing. |
663 | |
664 | On recent systems, the fact that perl requires 2M from system for 1M |
665 | allocation will not affect speed of execution, since the tail of such |
666 | a chunk is not going to be touched (and thus will not require real |
667 | memory). However, it may result in a premature out-of-memory error. |
668 | So if you will be manipulating very large blocks with sizes close to |
669 | powers of two, it would be wise to define this macro. |
670 | |
671 | Expected saving of memory is 0-100% (100% in applications which |
672 | require most memory in such 2**n chunks); expected slowdown is |
673 | negligible. |
674 | |
675 | =back |
676 | |
54310121 |
677 | =head2 Miscellaneous efficiency enhancements |
774d564b |
678 | |
679 | Functions that have an empty prototype and that do nothing but return |
680 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
681 | |
aa689395 |
682 | Each unique hash key is only allocated once, no matter how many hashes |
683 | have an entry with that key. So even if you have 100 copies of the |
68dc0745 |
684 | same hash, the hash keys never have to be reallocated. |
aa689395 |
685 | |
7bac28a0 |
686 | =head1 Support for More Operating Systems |
687 | |
688 | Support for the following operating systems is new in Perl 5.004. |
689 | |
690 | =head2 Win32 |
691 | |
692 | Perl 5.004 now includes support for building a "native" perl under |
693 | Windows NT, using the Microsoft Visual C++ compiler (versions 2.0 |
694 | and above). The resulting perl can be used under Windows 95 (if it |
695 | is installed in the same directory locations as it got installed |
696 | in Windows NT). This port includes support for perl extension |
697 | building tools like L<MakeMaker> and L<h2xs>, so that many extensions |
698 | available on the Comprehensive Perl Archive Network (CPAN) can now be |
699 | readily built under Windows NT. See http://www.perl.com/ for more |
700 | information on CPAN, and L<README.win32> for more details on how to |
701 | get started with building this port. |
702 | |
703 | There is also support for building perl under the Cygwin32 environment. |
704 | Cygwin32 is a set of GNU tools that make it possible to compile and run |
705 | many UNIX programs under Windows NT by providing a mostly UNIX-like |
706 | interface for compilation and execution. See L<README.cygwin32> for |
707 | more details on this port, and how to obtain the Cygwin32 toolkit. |
708 | This port has not been as well tested as the "native" port described |
709 | above (which is not as well tested as we'd like either :) |
710 | |
711 | =head2 Plan 9 |
712 | |
713 | See L<README.plan9>. |
714 | |
715 | =head2 QNX |
716 | |
717 | See L<README.qnx>. |
718 | |
719 | =head2 AmigaOS |
720 | |
721 | See L<README.amigaos>. |
722 | |
5f05dabc |
723 | =head1 Pragmata |
724 | |
54310121 |
725 | Six new pragmatic modules exist: |
5f05dabc |
726 | |
727 | =over |
728 | |
54310121 |
729 | =item use autouse MODULE => qw(sub1 sub2 sub3) |
730 | |
731 | Defers C<require MODULE> until someone calls one of the specified |
732 | subroutines (which must be exported by MODULE). This pragma should be |
733 | used with caution, and only when necessary. |
734 | |
5f05dabc |
735 | =item use blib |
736 | |
774d564b |
737 | =item use blib 'dir' |
738 | |
5f05dabc |
739 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
740 | I<dir> (or current directory) and working back up to five levels of |
741 | parent directories. |
742 | |
743 | Intended for use on command line with B<-M> option as a way of testing |
744 | arbitrary scripts against an uninstalled version of a package. |
745 | |
54310121 |
746 | =item use constant NAME => VALUE |
747 | |
748 | Provides a convenient interface for creating compile-time constants, |
749 | See L<perlsub/"Constant Functions">. |
750 | |
5f05dabc |
751 | =item use locale |
752 | |
753 | Tells the compiler to enable (or disable) the use of POSIX locales for |
54310121 |
754 | builtin operations. |
5f05dabc |
755 | |
756 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
757 | for regular expressions and case mapping; LC_COLLATE for string |
758 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
759 | (but B<not> in print). LC_NUMERIC is always used in write, since |
760 | lexical scoping of formats is problematic at best. |
761 | |
762 | Each C<use locale> or C<no locale> affects statements to the end of |
763 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
764 | current file. Locales can be switched and queried with |
765 | POSIX::setlocale(). |
766 | |
767 | See L<perllocale> for more information. |
768 | |
769 | =item use ops |
770 | |
7cfe7857 |
771 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
5f05dabc |
772 | |
ff0cee69 |
773 | =item use vmsish |
774 | |
775 | Enable VMS-specific language features. Currently, there are three |
aa689395 |
776 | VMS-specific features available: 'status', which makes C<$?> and |
ff0cee69 |
777 | C<system> return genuine VMS status values instead of emulating POSIX; |
778 | 'exit', which makes C<exit> take a genuine VMS status value instead of |
779 | assuming that C<exit 1> is an error; and 'time', which makes all times |
780 | relative to the local time zone, in the VMS tradition. |
781 | |
5f05dabc |
782 | =back |
783 | |
784 | =head1 Modules |
785 | |
5cd24f17 |
786 | =head2 Required Updates |
787 | |
788 | Though Perl 5.004 is compatible with almost all modules that work |
789 | with Perl 5.003, there are a few exceptions: |
790 | |
791 | Module Required Version for Perl 5.004 |
792 | ------ ------------------------------- |
137443ea |
793 | Filter Filter-1.12 |
794 | LWP libwww-perl-5.08 |
5cd24f17 |
795 | Tk Tk400.202 (-w makes noise) |
796 | |
137443ea |
797 | Also, the majordomo mailing list program, version 1.94.1, doesn't work |
798 | with Perl 5.004 (nor with perl 4), because it executes an invalid |
799 | regular expression. This bug is fixed in majordomo version 1.94.2. |
800 | |
54310121 |
801 | =head2 Installation directories |
f86702cc |
802 | |
803 | The I<installperl> script now places the Perl source files for |
804 | extensions in the architecture-specific library directory, which is |
805 | where the shared libraries for extensions have always been. This |
806 | change is intended to allow administrators to keep the Perl 5.004 |
807 | library directory unchanged from a previous version, without running |
808 | the risk of binary incompatibility between extensions' Perl source and |
809 | shared libraries. |
810 | |
54310121 |
811 | =head2 Module information summary |
5f05dabc |
812 | |
774d564b |
813 | Brand new modules, arranged by topic rather than strictly |
814 | alphabetically: |
815 | |
137443ea |
816 | CGI.pm Web server interface ("Common Gateway Interface") |
817 | CGI/Apache.pm Support for Apache's Perl module |
818 | CGI/Carp.pm Log server errors with helpful context |
819 | CGI/Fast.pm Support for FastCGI (persistent server process) |
820 | CGI/Push.pm Support for server push |
821 | CGI/Switch.pm Simple interface for multiple server types |
822 | |
823 | CPAN Interface to Comprehensive Perl Archive Network |
824 | CPAN::FirstTime Utility for creating CPAN configuration file |
825 | CPAN::Nox Runs CPAN while avoiding compiled extensions |
5f05dabc |
826 | |
827 | IO.pm Top-level interface to IO::* classes |
828 | IO/File.pm IO::File extension Perl module |
829 | IO/Handle.pm IO::Handle extension Perl module |
830 | IO/Pipe.pm IO::Pipe extension Perl module |
831 | IO/Seekable.pm IO::Seekable extension Perl module |
832 | IO/Select.pm IO::Select extension Perl module |
833 | IO/Socket.pm IO::Socket extension Perl module |
834 | |
835 | Opcode.pm Disable named opcodes when compiling Perl code |
836 | |
837 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
838 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
839 | |
5f05dabc |
840 | FindBin.pm Find path of currently executing program |
841 | |
8cc95fdb |
842 | Class/Struct.pm Declare struct-like datatypes as Perl classes |
46fc3d4c |
843 | File/stat.pm By-name interface to Perl's builtin stat |
844 | Net/hostent.pm By-name interface to Perl's builtin gethost* |
845 | Net/netent.pm By-name interface to Perl's builtin getnet* |
846 | Net/protoent.pm By-name interface to Perl's builtin getproto* |
847 | Net/servent.pm By-name interface to Perl's builtin getserv* |
848 | Time/gmtime.pm By-name interface to Perl's builtin gmtime |
849 | Time/localtime.pm By-name interface to Perl's builtin localtime |
8cc95fdb |
850 | Time/tm.pm Internal object for Time::{gm,local}time |
46fc3d4c |
851 | User/grent.pm By-name interface to Perl's builtin getgr* |
852 | User/pwent.pm By-name interface to Perl's builtin getpw* |
5f05dabc |
853 | |
774d564b |
854 | Tie/RefHash.pm Base class for tied hashes with references as keys |
7a4c00b4 |
855 | |
5f05dabc |
856 | UNIVERSAL.pm Base class for *ALL* classes |
857 | |
54310121 |
858 | =head2 Fcntl |
859 | |
860 | New constants in the existing Fcntl modules are now supported, |
861 | provided that your operating system happens to support them: |
862 | |
863 | F_GETOWN F_SETOWN |
864 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
865 | O_EXLOCK O_SHLOCK |
866 | |
867 | These constants are intended for use with the Perl operators sysopen() |
868 | and fcntl() and the basic database modules like SDBM_File. For the |
869 | exact meaning of these and other Fcntl constants please refer to your |
870 | operating system's documentation for fcntl() and open(). |
871 | |
872 | In addition, the Fcntl module now provides these constants for use |
873 | with the Perl operator flock(): |
874 | |
875 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN |
876 | |
877 | These constants are defined in all environments (because where there is |
878 | no flock() system call, Perl emulates it). However, for historical |
879 | reasons, these constants are not exported unless they are explicitly |
880 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>). |
881 | |
5f05dabc |
882 | =head2 IO |
883 | |
884 | The IO module provides a simple mechanism to load all of the IO modules at one |
885 | go. Currently this includes: |
886 | |
887 | IO::Handle |
888 | IO::Seekable |
889 | IO::File |
890 | IO::Pipe |
891 | IO::Socket |
892 | |
893 | For more information on any of these modules, please see its |
894 | respective documentation. |
895 | |
896 | =head2 Math::Complex |
897 | |
898 | The Math::Complex module has been totally rewritten, and now supports |
899 | more operations. These are overloaded: |
900 | |
901 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
902 | |
903 | And these functions are now exported: |
904 | |
905 | pi i Re Im arg |
5cd24f17 |
906 | log10 logn ln cbrt root |
907 | tan |
908 | csc sec cot |
909 | asin acos atan |
910 | acsc asec acot |
911 | sinh cosh tanh |
912 | csch sech coth |
913 | asinh acosh atanh |
914 | acsch asech acoth |
5f05dabc |
915 | cplx cplxe |
916 | |
5aabfad6 |
917 | =head2 Math::Trig |
918 | |
5cd24f17 |
919 | This new module provides a simpler interface to parts of Math::Complex for |
5aabfad6 |
920 | those who need trigonometric functions only for real numbers. |
921 | |
0a753a76 |
922 | =head2 DB_File |
923 | |
924 | There have been quite a few changes made to DB_File. Here are a few of |
925 | the highlights: |
926 | |
927 | =over |
928 | |
929 | =item * |
930 | |
931 | Fixed a handful of bugs. |
932 | |
933 | =item * |
934 | |
935 | By public demand, added support for the standard hash function exists(). |
936 | |
937 | =item * |
938 | |
939 | Made it compatible with Berkeley DB 1.86. |
940 | |
941 | =item * |
942 | |
943 | Made negative subscripts work with RECNO interface. |
944 | |
945 | =item * |
946 | |
947 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default |
948 | mode from 0640 to 0666. |
949 | |
950 | =item * |
951 | |
952 | Made DB_File automatically import the open() constants (O_RDWR, |
953 | O_CREAT etc.) from Fcntl, if available. |
954 | |
955 | =item * |
956 | |
957 | Updated documentation. |
958 | |
959 | =back |
960 | |
961 | Refer to the HISTORY section in DB_File.pm for a complete list of |
962 | changes. Everything after DB_File 1.01 has been added since 5.003. |
963 | |
964 | =head2 Net::Ping |
965 | |
966 | Major rewrite - support added for both udp echo and real icmp pings. |
967 | |
54310121 |
968 | =head2 Object-oriented overrides for builtin operators |
5f05dabc |
969 | |
54310121 |
970 | Many of the Perl builtins returning lists now have |
5f05dabc |
971 | object-oriented overrides. These are: |
972 | |
973 | File::stat |
974 | Net::hostent |
975 | Net::netent |
976 | Net::protoent |
977 | Net::servent |
978 | Time::gmtime |
979 | Time::localtime |
980 | User::grent |
981 | User::pwent |
982 | |
983 | For example, you can now say |
984 | |
985 | use File::stat; |
986 | use User::pwent; |
987 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
988 | |
774d564b |
989 | =head1 Utility Changes |
5f05dabc |
990 | |
7bac28a0 |
991 | =head2 pod2html |
992 | |
993 | =over |
994 | |
995 | =item Sends converted HTML to standard output |
996 | |
997 | The I<pod2html> utility included with Perl 5.004 is entirely new. |
998 | By default, it sends the converted HTML to its standard output, |
999 | instead of writing it to a file like Perl 5.003's I<pod2html> did. |
1000 | Use the B<--outfile=FILENAME> option to write to a file. |
1001 | |
1002 | =back |
1003 | |
774d564b |
1004 | =head2 xsubpp |
5f05dabc |
1005 | |
0a753a76 |
1006 | =over |
1007 | |
774d564b |
1008 | =item C<void> XSUBs now default to returning nothing |
1009 | |
1010 | Due to a documentation/implementation bug in previous versions of |
1011 | Perl, XSUBs with a return type of C<void> have actually been |
1012 | returning one value. Usually that value was the GV for the XSUB, |
1013 | but sometimes it was some already freed or reused value, which would |
1014 | sometimes lead to program failure. |
1015 | |
1016 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
1017 | actually returns no value, i.e. an empty list (though there is a |
1018 | backward-compatibility exception; see below). If your XSUB really |
1019 | does return an SV, you should give it a return type of C<SV *>. |
1020 | |
1021 | For backward compatibility, I<xsubpp> tries to guess whether a |
1022 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
1023 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
1024 | what looks like an assignment to C<ST(0)>, it assumes that the |
1025 | XSUB's return type is really C<SV *>. |
5f05dabc |
1026 | |
0a753a76 |
1027 | =back |
1028 | |
1029 | =head1 C Language API Changes |
1030 | |
1031 | =over |
1032 | |
1033 | =item C<gv_fetchmethod> and C<perl_call_sv> |
1034 | |
1035 | The C<gv_fetchmethod> function finds a method for an object, just like |
1036 | in Perl 5.003. The GV it returns may be a method cache entry. |
1037 | However, in Perl 5.004, method cache entries are not visible to users; |
1038 | therefore, they can no longer be passed directly to C<perl_call_sv>. |
1039 | Instead, you should use the C<GvCV> macro on the GV to extract its CV, |
1040 | and pass the CV to C<perl_call_sv>. |
1041 | |
1042 | The most likely symptom of passing the result of C<gv_fetchmethod> to |
1043 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called" |
1044 | error on the I<second> call to a given method (since there is no cache |
1045 | on the first call). |
1046 | |
137443ea |
1047 | =item C<perl_eval_pv> |
1048 | |
8903cb82 |
1049 | A new function handy for eval'ing strings of Perl code inside C code. |
137443ea |
1050 | This function returns the value from the eval statement, which can |
1051 | be used instead of fetching globals from the symbol table. See |
1052 | L<perlguts>, L<perlembed> and L<perlcall> for details and examples. |
1053 | |
1e422769 |
1054 | =item Extended API for manipulating hashes |
1055 | |
1056 | Internal handling of hash keys has changed. The old hashtable API is |
1057 | still fully supported, and will likely remain so. The additions to the |
1058 | API allow passing keys as C<SV*>s, so that C<tied> hashes can be given |
54310121 |
1059 | real scalars as keys rather than plain strings (nontied hashes still |
1e422769 |
1060 | can only use strings as keys). New extensions must use the new hash |
1061 | access functions and macros if they wish to use C<SV*> keys. These |
1062 | additions also make it feasible to manipulate C<HE*>s (hash entries), |
1063 | which can be more efficient. See L<perlguts> for details. |
1064 | |
0a753a76 |
1065 | =back |
1066 | |
5f05dabc |
1067 | =head1 Documentation Changes |
1068 | |
1069 | Many of the base and library pods were updated. These |
1070 | new pods are included in section 1: |
1071 | |
0a753a76 |
1072 | =over |
5f05dabc |
1073 | |
774d564b |
1074 | =item L<perldelta> |
5f05dabc |
1075 | |
71be2cbc |
1076 | This document. |
5f05dabc |
1077 | |
c90c0ff4 |
1078 | =item L<perlfaq> |
1079 | |
1080 | Frequently asked questions. |
1081 | |
71be2cbc |
1082 | =item L<perllocale> |
5f05dabc |
1083 | |
71be2cbc |
1084 | Locale support (internationalization and localization). |
5f05dabc |
1085 | |
1086 | =item L<perltoot> |
1087 | |
1088 | Tutorial on Perl OO programming. |
1089 | |
71be2cbc |
1090 | =item L<perlapio> |
1091 | |
1092 | Perl internal IO abstraction interface. |
1093 | |
c90c0ff4 |
1094 | =item L<perlmodlib> |
1095 | |
1096 | Perl module library and recommended practice for module creation. |
1097 | Extracted from L<perlmod> (which is much smaller as a result). |
1098 | |
5f05dabc |
1099 | =item L<perldebug> |
1100 | |
1101 | Although not new, this has been massively updated. |
1102 | |
1103 | =item L<perlsec> |
1104 | |
1105 | Although not new, this has been massively updated. |
1106 | |
1107 | =back |
1108 | |
1109 | =head1 New Diagnostics |
1110 | |
1111 | Several new conditions will trigger warnings that were |
1112 | silent before. Some only affect certain platforms. |
2ae324a7 |
1113 | The following new warnings and errors outline these. |
774d564b |
1114 | These messages are classified as follows (listed in |
1115 | increasing order of desperation): |
1116 | |
1117 | (W) A warning (optional). |
1118 | (D) A deprecation (optional). |
1119 | (S) A severe warning (mandatory). |
1120 | (F) A fatal error (trappable). |
1121 | (P) An internal error you should never see (trappable). |
54310121 |
1122 | (X) A very fatal error (nontrappable). |
774d564b |
1123 | (A) An alien error message (not generated by Perl). |
5f05dabc |
1124 | |
0a753a76 |
1125 | =over |
5f05dabc |
1126 | |
1127 | =item "my" variable %s masks earlier declaration in same scope |
1128 | |
1129 | (S) A lexical variable has been redeclared in the same scope, effectively |
1130 | eliminating all access to the previous instance. This is almost always |
1131 | a typographical error. Note that the earlier variable will still exist |
1132 | until the end of the scope or until all closure referents to it are |
1133 | destroyed. |
1134 | |
774d564b |
1135 | =item %s argument is not a HASH element or slice |
1136 | |
1137 | (F) The argument to delete() must be either a hash element, such as |
1138 | |
1139 | $foo{$bar} |
1140 | $ref->[12]->{"susie"} |
1141 | |
1142 | or a hash slice, such as |
1143 | |
1144 | @foo{$bar, $baz, $xyzzy} |
1145 | @{$ref->[12]}{"susie", "queue"} |
1146 | |
5f05dabc |
1147 | =item Allocation too large: %lx |
1148 | |
54310121 |
1149 | (X) You can't allocate more than 64K on an MS-DOS machine. |
5f05dabc |
1150 | |
1151 | =item Allocation too large |
1152 | |
1153 | (F) You can't allocate more than 2^31+"small amount" bytes. |
1154 | |
54310121 |
1155 | =item Applying %s to %s will act on scalar(%s) |
1156 | |
1157 | (W) The pattern match (//), substitution (s///), and translation (tr///) |
1158 | operators work on scalar values. If you apply one of them to an array |
1159 | or a hash, it will convert the array or hash to a scalar value -- the |
1160 | length of an array, or the population info of a hash -- and then work on |
1161 | that scalar value. This is probably not what you meant to do. See |
1162 | L<perlfunc/grep> and L<perlfunc/map> for alternatives. |
1163 | |
1164 | =item Attempt to free nonexistent shared string |
5f05dabc |
1165 | |
1166 | (P) Perl maintains a reference counted internal table of strings to |
1167 | optimize the storage and access of hash keys and other strings. This |
1168 | indicates someone tried to decrement the reference count of a string |
1169 | that can no longer be found in the table. |
1170 | |
1171 | =item Attempt to use reference as lvalue in substr |
1172 | |
1173 | (W) You supplied a reference as the first argument to substr() used |
1174 | as an lvalue, which is pretty strange. Perhaps you forgot to |
1175 | dereference it first. See L<perlfunc/substr>. |
1176 | |
7bac28a0 |
1177 | =item Can't redefine active sort subroutine %s |
1178 | |
1179 | (F) Perl optimizes the internal handling of sort subroutines and keeps |
1180 | pointers into them. You tried to redefine one such sort subroutine when it |
1181 | was currently active, which is not allowed. If you really want to do |
1182 | this, you should write C<sort { &func } @x> instead of C<sort func @x>. |
1183 | |
774d564b |
1184 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
1185 | |
1186 | (F) Only hard references are allowed by "strict refs". Symbolic references |
1187 | are disallowed. See L<perlref>. |
1188 | |
54310121 |
1189 | =item Cannot resolve method `%s' overloading `%s' in package `%s' |
1190 | |
1191 | (P) Internal error trying to resolve overloading specified by a method |
1192 | name (as opposed to a subroutine reference). |
1193 | |
774d564b |
1194 | =item Constant subroutine %s redefined |
1195 | |
1196 | (S) You redefined a subroutine which had previously been eligible for |
dc848c6f |
1197 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
54310121 |
1198 | workarounds. |
1199 | |
1200 | =item Constant subroutine %s undefined |
1201 | |
1202 | (S) You undefined a subroutine which had previously been eligible for |
774d564b |
1203 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
1204 | workarounds. |
1205 | |
54310121 |
1206 | =item Copy method did not return a reference |
1207 | |
1208 | (F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>. |
1209 | |
774d564b |
1210 | =item Died |
1211 | |
1212 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
1213 | you called it with no args and both C<$@> and C<$_> were empty. |
1214 | |
54310121 |
1215 | =item Exiting pseudo-block via %s |
1216 | |
1217 | (W) You are exiting a rather special block construct (like a sort block or |
1218 | subroutine) by unconventional means, such as a goto, or a loop control |
1219 | statement. See L<perlfunc/sort>. |
1220 | |
8903cb82 |
1221 | =item Identifier too long |
1222 | |
1223 | (F) Perl limits identifiers (names for variables, functions, etc.) to |
1224 | 252 characters for simple names, somewhat more for compound names (like |
1225 | C<$A::B>). You've exceeded Perl's limits. Future versions of Perl are |
1226 | likely to eliminate these arbitrary limitations. |
1227 | |
54310121 |
1228 | =item Illegal character %s (carriage return) |
1229 | |
1230 | (F) A carriage return character was found in the input. This is an |
1231 | error, and not a warning, because carriage return characters can break |
1232 | multi-line strings, including here documents (e.g., C<print E<lt>E<lt>EOF;>). |
1233 | |
1234 | =item Illegal switch in PERL5OPT: %s |
1235 | |
1236 | (X) The PERL5OPT environment variable may only be used to set the |
1237 | following switches: B<-[DIMUdmw]>. |
1238 | |
5f05dabc |
1239 | =item Integer overflow in hex number |
1240 | |
1241 | (S) The literal hex number you have specified is too big for your |
1242 | architecture. On a 32-bit architecture the largest hex literal is |
1243 | 0xFFFFFFFF. |
1244 | |
1245 | =item Integer overflow in octal number |
1246 | |
1247 | (S) The literal octal number you have specified is too big for your |
1248 | architecture. On a 32-bit architecture the largest octal literal is |
1249 | 037777777777. |
1250 | |
5cd24f17 |
1251 | =item internal error: glob failed |
1252 | |
1253 | (P) Something went wrong with the external program(s) used for C<glob> |
1254 | and C<E<lt>*.cE<gt>>. This may mean that your csh (C shell) is |
1255 | broken. If so, you should change all of the csh-related variables in |
1256 | config.sh: If you have tcsh, make the variables refer to it as if it |
1257 | were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all |
1258 | empty (except that C<d_csh> should be C<'undef'>) so that Perl will |
1259 | think csh is missing. In either case, after editing config.sh, run |
1260 | C<./Configure -S> and rebuild Perl. |
1261 | |
878e08df |
1262 | =item Invalid conversion in %s: "%s" |
1263 | |
1264 | (W) Perl does not understand the given format conversion. |
1265 | See L<perlfunc/sprintf>. |
1266 | |
8903cb82 |
1267 | =item Invalid type in pack: '%s' |
1268 | |
1269 | (F) The given character is not a valid pack type. See L<perlfunc/pack>. |
1270 | |
1271 | =item Invalid type in unpack: '%s' |
1272 | |
1273 | (F) The given character is not a valid unpack type. See L<perlfunc/unpack>. |
1274 | |
774d564b |
1275 | =item Name "%s::%s" used only once: possible typo |
1276 | |
1277 | (W) Typographical errors often show up as unique variable names. |
1278 | If you had a good reason for having a unique name, then just mention |
1279 | it again somehow to suppress the message (the C<use vars> pragma is |
1280 | provided for just this purpose). |
1281 | |
5f05dabc |
1282 | =item Null picture in formline |
1283 | |
1284 | (F) The first argument to formline must be a valid format picture |
1285 | specification. It was found to be empty, which probably means you |
1286 | supplied it an uninitialized value. See L<perlform>. |
1287 | |
1288 | =item Offset outside string |
1289 | |
1290 | (F) You tried to do a read/write/send/recv operation with an offset |
1291 | pointing outside the buffer. This is difficult to imagine. |
1292 | The sole exception to this is that C<sysread()>ing past the buffer |
1293 | will extend the buffer and zero pad the new area. |
1294 | |
1295 | =item Out of memory! |
1296 | |
1297 | (X|F) The malloc() function returned 0, indicating there was insufficient |
1298 | remaining memory (or virtual memory) to satisfy the request. |
1299 | |
1300 | The request was judged to be small, so the possibility to trap it |
1301 | depends on the way Perl was compiled. By default it is not trappable. |
1302 | However, if compiled for this, Perl may use the contents of C<$^M> as |
1303 | an emergency pool after die()ing with this message. In this case the |
1304 | error is trappable I<once>. |
1305 | |
1306 | =item Out of memory during request for %s |
1307 | |
1308 | (F) The malloc() function returned 0, indicating there was insufficient |
1309 | remaining memory (or virtual memory) to satisfy the request. However, |
1310 | the request was judged large enough (compile-time default is 64K), so |
1311 | a possibility to shut down by trapping this error is granted. |
1312 | |
878e08df |
1313 | =item panic: frexp |
1314 | |
1315 | (P) The library function frexp() failed, making printf("%f") impossible. |
1316 | |
5f05dabc |
1317 | =item Possible attempt to put comments in qw() list |
1318 | |
774d564b |
1319 | (W) qw() lists contain items separated by whitespace; as with literal |
1320 | strings, comment characters are not ignored, but are instead treated |
1321 | as literal data. (You may have used different delimiters than the |
1322 | exclamation marks parentheses shown here; braces are also frequently |
1323 | used.) |
1324 | |
1325 | You probably wrote something like this: |
5f05dabc |
1326 | |
2ae324a7 |
1327 | @list = qw( |
774d564b |
1328 | a # a comment |
5f05dabc |
1329 | b # another comment |
774d564b |
1330 | ); |
5f05dabc |
1331 | |
1332 | when you should have written this: |
1333 | |
774d564b |
1334 | @list = qw( |
2ae324a7 |
1335 | a |
5f05dabc |
1336 | b |
774d564b |
1337 | ); |
1338 | |
1339 | If you really want comments, build your list the |
1340 | old-fashioned way, with quotes and commas: |
1341 | |
1342 | @list = ( |
1343 | 'a', # a comment |
1344 | 'b', # another comment |
1345 | ); |
5f05dabc |
1346 | |
1347 | =item Possible attempt to separate words with commas |
1348 | |
774d564b |
1349 | (W) qw() lists contain items separated by whitespace; therefore commas |
1350 | aren't needed to separate the items. (You may have used different |
1351 | delimiters than the parentheses shown here; braces are also frequently |
1352 | used.) |
5f05dabc |
1353 | |
2ae324a7 |
1354 | You probably wrote something like this: |
5f05dabc |
1355 | |
774d564b |
1356 | qw! a, b, c !; |
1357 | |
1358 | which puts literal commas into some of the list items. Write it without |
1359 | commas if you don't want them to appear in your data: |
1360 | |
1361 | qw! a b c !; |
5f05dabc |
1362 | |
774d564b |
1363 | =item Scalar value @%s{%s} better written as $%s{%s} |
1364 | |
1365 | (W) You've used a hash slice (indicated by @) to select a single element of |
1366 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
1367 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
1368 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
1369 | like a list when you assign to it, and provides a list context to its |
1370 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
1371 | |
54310121 |
1372 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
1373 | |
1374 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
1375 | Stubs should never be implicitely created, but explicit calls to C<can> |
1376 | may break this. |
1377 | |
1378 | =item Too late for "B<-T>" option |
1379 | |
1380 | (X) The #! line (or local equivalent) in a Perl script contains the |
1381 | B<-T> option, but Perl was not invoked with B<-T> in its argument |
1382 | list. This is an error because, by the time Perl discovers a B<-T> in |
1383 | a script, it's too late to properly taint everything from the |
1384 | environment. So Perl gives up. |
1385 | |
5f05dabc |
1386 | =item untie attempted while %d inner references still exist |
1387 | |
1388 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
1389 | valid when C<untie> was called. |
1390 | |
54310121 |
1391 | =item Unrecognized character %s |
1392 | |
1393 | (F) The Perl parser has no idea what to do with the specified character |
1394 | in your Perl script (or eval). Perhaps you tried to run a compressed |
1395 | script, a binary program, or a directory as a Perl program. |
1396 | |
1397 | =item Unsupported function fork |
1398 | |
1399 | (F) Your version of executable does not support forking. |
1400 | |
1401 | Note that under some systems, like OS/2, there may be different flavors of |
1402 | Perl executables, some of which may support fork, some not. Try changing |
1403 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
1404 | |
5cd24f17 |
1405 | =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated |
1406 | |
1407 | (D) Perl versions before 5.004 misinterpreted any type marker followed |
1408 | by "$" and a digit. For example, "$$0" was incorrectly taken to mean |
1409 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
1410 | |
1411 | However, the developers of Perl 5.004 could not fix this bug completely, |
1412 | because at least two widely-used modules depend on the old meaning of |
1413 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
1414 | old (broken) way inside strings; but it generates this message as a |
1415 | warning. And in Perl 5.005, this special treatment will cease. |
1416 | |
54310121 |
1417 | =item Value of %s can be "0"; test with defined() |
774d564b |
1418 | |
54310121 |
1419 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>, |
1420 | or C<readdir()> as a boolean value. Each of these constructs can return a |
1421 | value of "0"; that would make the conditional expression false, which is |
1422 | probably not what you intended. When using these constructs in conditional |
1423 | expressions, test their values with the C<defined> operator. |
774d564b |
1424 | |
1425 | =item Variable "%s" may be unavailable |
1426 | |
1427 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
1428 | subroutine, and outside that is another subroutine; and the anonymous |
1429 | (innermost) subroutine is referencing a lexical variable defined in |
1430 | the outermost subroutine. For example: |
1431 | |
1432 | sub outermost { my $a; sub middle { sub { $a } } } |
1433 | |
1434 | If the anonymous subroutine is called or referenced (directly or |
1435 | indirectly) from the outermost subroutine, it will share the variable |
1436 | as you would expect. But if the anonymous subroutine is called or |
1437 | referenced when the outermost subroutine is not active, it will see |
1438 | the value of the shared variable as it was before and during the |
1439 | *first* call to the outermost subroutine, which is probably not what |
1440 | you want. |
1441 | |
1442 | In these circumstances, it is usually best to make the middle |
1443 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
1444 | support for shared variables in nested anonymous subroutines; a named |
1445 | subroutine in between interferes with this feature. |
1446 | |
1447 | =item Variable "%s" will not stay shared |
1448 | |
1449 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
1450 | variable defined in an outer subroutine. |
1451 | |
1452 | When the inner subroutine is called, it will probably see the value of |
1453 | the outer subroutine's variable as it was before and during the |
1454 | *first* call to the outer subroutine; in this case, after the first |
1455 | call to the outer subroutine is complete, the inner and outer |
1456 | subroutines will no longer share a common value for the variable. In |
1457 | other words, the variable will no longer be shared. |
1458 | |
1459 | Furthermore, if the outer subroutine is anonymous and references a |
1460 | lexical variable outside itself, then the outer and inner subroutines |
1461 | will I<never> share the given variable. |
1462 | |
1463 | This problem can usually be solved by making the inner subroutine |
1464 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
1465 | reference variables in outer subroutines are called or referenced, |
54310121 |
1466 | they are automatically rebound to the current values of such |
774d564b |
1467 | variables. |
1468 | |
1469 | =item Warning: something's wrong |
1470 | |
1471 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
1472 | you called it with no args and C<$_> was empty. |
1473 | |
54310121 |
1474 | =item Ill-formed logical name |%s| in prime_env_iter |
1475 | |
1476 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
1477 | to iterate over %ENV which violates the syntactic rules governing logical |
1478 | names. Since it cannot be translated normally, it is skipped, and will not |
1479 | appear in %ENV. This may be a benign occurrence, as some software packages |
1480 | might directly modify logical name tables and introduce nonstandard names, |
1481 | or it may indicate that a logical name table has been corrupted. |
1482 | |
774d564b |
1483 | =item Got an error from DosAllocMem |
5f05dabc |
1484 | |
774d564b |
1485 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
1486 | version of Perl, and this should not happen anyway. |
5f05dabc |
1487 | |
1488 | =item Malformed PERLLIB_PREFIX |
1489 | |
dc848c6f |
1490 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
5f05dabc |
1491 | |
1492 | prefix1;prefix2 |
1493 | |
1494 | or |
1495 | |
1496 | prefix1 prefix2 |
1497 | |
dc848c6f |
1498 | with nonempty prefix1 and prefix2. If C<prefix1> is indeed a prefix |
1499 | of a builtin library search path, prefix2 is substituted. The error |
1500 | may appear if components are not found, or are too long. See |
1501 | "PERLLIB_PREFIX" in F<README.os2>. |
5f05dabc |
1502 | |
1503 | =item PERL_SH_DIR too long |
1504 | |
1505 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
dc848c6f |
1506 | C<sh>-shell in. See "PERL_SH_DIR" in F<README.os2>. |
5f05dabc |
1507 | |
1508 | =item Process terminated by SIG%s |
1509 | |
1510 | (W) This is a standard message issued by OS/2 applications, while *nix |
dc848c6f |
1511 | applications die in silence. It is considered a feature of the OS/2 |
1512 | port. One can easily disable this by appropriate sighandlers, see |
1513 | L<perlipc/"Signals">. See also "Process terminated by SIGTERM/SIGINT" |
1514 | in F<README.os2>. |
5f05dabc |
1515 | |
1516 | =back |
1517 | |
1518 | =head1 BUGS |
1519 | |
774d564b |
1520 | If you find what you think is a bug, you might check the headers of |
1521 | recently posted articles in the comp.lang.perl.misc newsgroup. |
1522 | There may also be information at http://www.perl.com/perl/, the Perl |
1523 | Home Page. |
5f05dabc |
1524 | |
1525 | If you believe you have an unreported bug, please run the B<perlbug> |
9607fc9c |
1526 | program included with your release. Make sure you trim your bug down |
1527 | to a tiny but sufficient test case. Your bug report, along with the |
1528 | output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be |
1529 | analysed by the Perl porting team. |
5f05dabc |
1530 | |
1531 | =head1 SEE ALSO |
1532 | |
1533 | The F<Changes> file for exhaustive details on what changed. |
1534 | |
1535 | The F<INSTALL> file for how to build Perl. This file has been |
1536 | significantly updated for 5.004, so even veteran users should |
1537 | look through it. |
1538 | |
1539 | The F<README> file for general stuff. |
1540 | |
1541 | The F<Copying> file for copyright information. |
1542 | |
1543 | =head1 HISTORY |
1544 | |
1545 | Constructed by Tom Christiansen, grabbing material with permission |
1546 | from innumerable contributors, with kibitzing by more than a few Perl |
1547 | porters. |
1548 | |
c90c0ff4 |
1549 | Last update: Wed May 14 11:14:09 EDT 1997 |