Commit | Line | Data |
3176feef |
1 | package Try::Tiny; |
12b7dc6c |
2 | use 5.006; |
3 | # ABSTRACT: minimal try/catch with proper preservation of $@ |
3176feef |
4 | |
5 | use strict; |
f9d19a00 |
6 | use warnings; |
3176feef |
7 | |
b4207115 |
8 | use Exporter 5.57 'import'; |
f9d19a00 |
9 | our @EXPORT = our @EXPORT_OK = qw(try catch finally); |
3176feef |
10 | |
f9d19a00 |
11 | use Carp; |
6f114080 |
12 | $Carp::Internal{+__PACKAGE__}++; |
13 | |
5c9d800f |
14 | BEGIN { eval "use Sub::Name; 1" or *{subname} = sub {1} } |
15 | |
7195fc08 |
16 | # Need to prototype as @ not $$ because of the way Perl evaluates the prototype. |
17 | # Keeping it at $$ means you only ever get 1 sub because we need to eval in a list |
18 | # context & not a scalar one |
19 | |
20 | sub try (&;@) { |
8d2ee831 |
21 | my ( $try, @code_refs ) = @_; |
22 | |
23 | # we need to save this here, the eval block will be in scalar context due |
24 | # to $failed |
25 | my $wantarray = wantarray; |
26 | |
130617d9 |
27 | # work around perl bug by explicitly initializing these, due to the likelyhood |
28 | # this will be used in global destruction (perl rt#119311) |
29 | my ( $catch, @finally ) = (); |
8d2ee831 |
30 | |
31 | # find labeled blocks in the argument list. |
32 | # catch and finally tag the blocks by blessing a scalar reference to them. |
33 | foreach my $code_ref (@code_refs) { |
8d2ee831 |
34 | |
4c5b99d6 |
35 | if ( ref($code_ref) eq 'Try::Tiny::Catch' ) { |
9d0e0466 |
36 | croak 'A try() may not be followed by multiple catch() blocks' |
37 | if $catch; |
8d2ee831 |
38 | $catch = ${$code_ref}; |
4c5b99d6 |
39 | } elsif ( ref($code_ref) eq 'Try::Tiny::Finally' ) { |
8d2ee831 |
40 | push @finally, ${$code_ref}; |
41 | } else { |
4c5b99d6 |
42 | croak( |
43 | 'try() encountered an unexpected argument (' |
44 | . ( defined $code_ref ? $code_ref : 'undef' ) |
45 | . ') - perhaps a missing semi-colon before or' |
46 | ); |
8d2ee831 |
47 | } |
48 | } |
49 | |
2b0d579d |
50 | # FIXME consider using local $SIG{__DIE__} to accumulate all errors. It's |
51 | # not perfect, but we could provide a list of additional errors for |
52 | # $catch->(); |
53 | |
5c9d800f |
54 | # name the blocks if we have Sub::Name installed |
1131a831 |
55 | my $caller = caller; |
faa955ce |
56 | subname("${caller}::try {...} " => $try); |
1131a831 |
57 | subname("${caller}::catch {...} " => $catch) if $catch; |
58 | subname("${caller}::finally {...} " => $_) foreach @finally; |
5c9d800f |
59 | |
8d2ee831 |
60 | # save the value of $@ so we can set $@ back to it in the beginning of the eval |
2b0d579d |
61 | # and restore $@ after the eval finishes |
8d2ee831 |
62 | my $prev_error = $@; |
63 | |
2b0d579d |
64 | my ( @ret, $error ); |
8d2ee831 |
65 | |
2b0d579d |
66 | # failed will be true if the eval dies, because 1 will not be returned |
67 | # from the eval body |
68 | my $failed = not eval { |
69 | $@ = $prev_error; |
8d2ee831 |
70 | |
2b0d579d |
71 | # evaluate the try block in the correct context |
72 | if ( $wantarray ) { |
73 | @ret = $try->(); |
74 | } elsif ( defined $wantarray ) { |
75 | $ret[0] = $try->(); |
76 | } else { |
77 | $try->(); |
8d2ee831 |
78 | }; |
79 | |
2b0d579d |
80 | return 1; # properly set $fail to false |
3db0dca6 |
81 | }; |
2b0d579d |
82 | |
3db0dca6 |
83 | # preserve the current error and reset the original value of $@ |
84 | $error = $@; |
2b0d579d |
85 | $@ = $prev_error; |
8d2ee831 |
86 | |
87 | # set up a scope guard to invoke the finally block at the end |
88 | my @guards = |
b611f396 |
89 | map { Try::Tiny::ScopeGuard->_new($_, $failed ? $error : ()) } |
90 | @finally; |
82ef0e61 |
91 | |
8d2ee831 |
92 | # at this point $failed contains a true value if the eval died, even if some |
93 | # destructor overwrote $@ as the eval was unwinding. |
94 | if ( $failed ) { |
95 | # if we got an error, invoke the catch block. |
96 | if ( $catch ) { |
97 | # This works like given($error), but is backwards compatible and |
98 | # sets $_ in the dynamic scope for the body of C<$catch> |
99 | for ($error) { |
100 | return $catch->($error); |
101 | } |
102 | |
103 | # in case when() was used without an explicit return, the C<for> |
104 | # loop will be aborted and there's no useful return value |
105 | } |
106 | |
107 | return; |
108 | } else { |
109 | # no failure, $@ is back to what it was, everything is fine |
110 | return $wantarray ? @ret : $ret[0]; |
111 | } |
3176feef |
112 | } |
113 | |
7195fc08 |
114 | sub catch (&;@) { |
8d2ee831 |
115 | my ( $block, @rest ) = @_; |
7195fc08 |
116 | |
d2ae14ad |
117 | croak 'Useless bare catch()' unless wantarray; |
9d0e0466 |
118 | |
8d2ee831 |
119 | return ( |
120 | bless(\$block, 'Try::Tiny::Catch'), |
121 | @rest, |
122 | ); |
3176feef |
123 | } |
124 | |
7195fc08 |
125 | sub finally (&;@) { |
8d2ee831 |
126 | my ( $block, @rest ) = @_; |
7195fc08 |
127 | |
d2ae14ad |
128 | croak 'Useless bare finally()' unless wantarray; |
9d0e0466 |
129 | |
8d2ee831 |
130 | return ( |
131 | bless(\$block, 'Try::Tiny::Finally'), |
132 | @rest, |
133 | ); |
7195fc08 |
134 | } |
3176feef |
135 | |
b611f396 |
136 | { |
3ef3a4f0 |
137 | package # hide from PAUSE |
138 | Try::Tiny::ScopeGuard; |
b611f396 |
139 | |
5f5e92c0 |
140 | use constant UNSTABLE_DOLLARAT => ($] < '5.013002') ? 1 : 0; |
141 | |
b611f396 |
142 | sub _new { |
143 | shift; |
144 | bless [ @_ ]; |
145 | } |
146 | |
147 | sub DESTROY { |
5f5e92c0 |
148 | my ($code, @args) = @{ $_[0] }; |
149 | |
150 | local $@ if UNSTABLE_DOLLARAT; |
151 | eval { |
152 | $code->(@args); |
153 | 1; |
154 | } or do { |
155 | warn |
156 | "Execution of finally() block $code resulted in an exception, which " |
157 | . '*CAN NOT BE PROPAGATED* due to fundamental limitations of Perl. ' |
158 | . 'Your program will continue as if this event never took place. ' |
159 | . "Original exception text follows:\n\n" |
160 | . (defined $@ ? $@ : '$@ left undefined...') |
161 | . "\n" |
162 | ; |
163 | } |
b611f396 |
164 | } |
82ef0e61 |
165 | } |
166 | |
3176feef |
167 | __PACKAGE__ |
168 | |
169 | __END__ |
170 | |
171 | =pod |
172 | |
3176feef |
173 | =head1 SYNOPSIS |
174 | |
a2358317 |
175 | You can use Try::Tiny's C<try> and C<catch> to expect and handle exceptional |
176 | conditions, avoiding quirks in Perl and common mistakes: |
177 | |
8d2ee831 |
178 | # handle errors with a catch handler |
179 | try { |
180 | die "foo"; |
181 | } catch { |
182 | warn "caught error: $_"; # not $@ |
183 | }; |
3176feef |
184 | |
b999823d |
185 | You can also use it like a standalone C<eval> to catch and ignore any error |
a2358317 |
186 | conditions. Obviously, this is an extreme measure not to be undertaken |
187 | lightly: |
188 | |
8d2ee831 |
189 | # just silence errors |
190 | try { |
191 | die "foo"; |
192 | }; |
3176feef |
193 | |
194 | =head1 DESCRIPTION |
195 | |
7195fc08 |
196 | This module provides bare bones C<try>/C<catch>/C<finally> statements that are designed to |
1f7c5af6 |
197 | minimize common mistakes with eval blocks, and NOTHING else. |
3176feef |
198 | |
199 | This is unlike L<TryCatch> which provides a nice syntax and avoids adding |
ad10a9e2 |
200 | another call stack layer, and supports calling C<return> from the C<try> block to |
3176feef |
201 | return from the parent subroutine. These extra features come at a cost of a few |
202 | dependencies, namely L<Devel::Declare> and L<Scope::Upper> which are |
1f7c5af6 |
203 | occasionally problematic, and the additional catch filtering uses L<Moose> |
204 | type constraints which may not be desirable either. |
3176feef |
205 | |
1f7c5af6 |
206 | The main focus of this module is to provide simple and reliable error handling |
3176feef |
207 | for those having a hard time installing L<TryCatch>, but who still want to |
208 | write correct C<eval> blocks without 5 lines of boilerplate each time. |
209 | |
210 | It's designed to work as correctly as possible in light of the various |
b999823d |
211 | pathological edge cases (see L</BACKGROUND>) and to be compatible with any style |
3176feef |
212 | of error values (simple strings, references, objects, overloaded objects, etc). |
213 | |
ad10a9e2 |
214 | If the C<try> block dies, it returns the value of the last statement executed in |
215 | the C<catch> block, if there is one. Otherwise, it returns C<undef> in scalar |
c065237e |
216 | context or the empty list in list context. The following examples all |
ad10a9e2 |
217 | assign C<"bar"> to C<$x>: |
a5cd5f73 |
218 | |
8d2ee831 |
219 | my $x = try { die "foo" } catch { "bar" }; |
220 | my $x = try { die "foo" } || { "bar" }; |
221 | my $x = (try { die "foo" }) // { "bar" }; |
a5cd5f73 |
222 | |
8d2ee831 |
223 | my $x = eval { die "foo" } || "bar"; |
a5cd5f73 |
224 | |
ad10a9e2 |
225 | You can add C<finally> blocks, yielding the following: |
7195fc08 |
226 | |
8d2ee831 |
227 | my $x; |
228 | try { die 'foo' } finally { $x = 'bar' }; |
229 | try { die 'foo' } catch { warn "Got a die: $_" } finally { $x = 'bar' }; |
7195fc08 |
230 | |
ad10a9e2 |
231 | C<finally> blocks are always executed making them suitable for cleanup code |
232 | which cannot be handled using local. You can add as many C<finally> blocks to a |
233 | given C<try> block as you like. |
7195fc08 |
234 | |
3176feef |
235 | =head1 EXPORTS |
236 | |
1f7c5af6 |
237 | All functions are exported by default using L<Exporter>. |
3176feef |
238 | |
7195fc08 |
239 | If you need to rename the C<try>, C<catch> or C<finally> keyword consider using |
6157bcb8 |
240 | L<Sub::Import> to get L<Sub::Exporter>'s flexibility. |
3176feef |
241 | |
242 | =over 4 |
243 | |
7195fc08 |
244 | =item try (&;@) |
3176feef |
245 | |
ad10a9e2 |
246 | Takes one mandatory C<try> subroutine, an optional C<catch> subroutine and C<finally> |
7195fc08 |
247 | subroutine. |
3176feef |
248 | |
249 | The mandatory subroutine is evaluated in the context of an C<eval> block. |
250 | |
1f7c5af6 |
251 | If no error occurred the value from the first block is returned, preserving |
252 | list/scalar context. |
3176feef |
253 | |
254 | If there was an error and the second subroutine was given it will be invoked |
255 | with the error in C<$_> (localized) and as that block's first and only |
256 | argument. |
257 | |
2dc64249 |
258 | C<$@> does B<not> contain the error. Inside the C<catch> block it has the same |
259 | value it had before the C<try> block was executed. |
260 | |
1f7c5af6 |
261 | Note that the error may be false, but if that happens the C<catch> block will |
1d64c1ad |
262 | still be invoked. |
3176feef |
263 | |
ad10a9e2 |
264 | Once all execution is finished then the C<finally> block, if given, will execute. |
7195fc08 |
265 | |
ae5ed1be |
266 | =item catch (&;@) |
1f7c5af6 |
267 | |
268 | Intended to be used in the second argument position of C<try>. |
3176feef |
269 | |
7195fc08 |
270 | Returns a reference to the subroutine it was given but blessed as |
271 | C<Try::Tiny::Catch> which allows try to decode correctly what to do |
272 | with this code reference. |
3176feef |
273 | |
8d2ee831 |
274 | catch { ... } |
3176feef |
275 | |
ad10a9e2 |
276 | Inside the C<catch> block the caught error is stored in C<$_>, while previous |
2dc64249 |
277 | value of C<$@> is still available for use. This value may or may not be |
278 | meaningful depending on what happened before the C<try>, but it might be a good |
279 | idea to preserve it in an error stack. |
ac4f5f9f |
280 | |
0a0641f9 |
281 | For code that captures C<$@> when throwing new errors (i.e. |
282 | L<Class::Throwable>), you'll need to do: |
283 | |
8d2ee831 |
284 | local $@ = $_; |
0a0641f9 |
285 | |
ae5ed1be |
286 | =item finally (&;@) |
7195fc08 |
287 | |
288 | try { ... } |
289 | catch { ... } |
290 | finally { ... }; |
291 | |
292 | Or |
293 | |
294 | try { ... } |
295 | finally { ... }; |
296 | |
297 | Or even |
298 | |
299 | try { ... } |
300 | finally { ... } |
301 | catch { ... }; |
302 | |
ad10a9e2 |
303 | Intended to be the second or third element of C<try>. C<finally> blocks are always |
7195fc08 |
304 | executed in the event of a successful C<try> or if C<catch> is run. This allows |
305 | you to locate cleanup code which cannot be done via C<local()> e.g. closing a file |
306 | handle. |
307 | |
ad10a9e2 |
308 | When invoked, the C<finally> block is passed the error that was caught. If no |
309 | error was caught, it is passed nothing. (Note that the C<finally> block does not |
310 | localize C<$_> with the error, since unlike in a C<catch> block, there is no way |
658a90e5 |
311 | to know if C<$_ == undef> implies that there were no errors.) In other words, |
312 | the following code does just what you would expect: |
d6e0f0df |
313 | |
314 | try { |
315 | die_sometimes(); |
316 | } catch { |
317 | # ...code run in case of error |
318 | } finally { |
319 | if (@_) { |
320 | print "The try block died with: @_\n"; |
321 | } else { |
322 | print "The try block ran without error.\n"; |
323 | } |
324 | }; |
325 | |
ad10a9e2 |
326 | B<You must always do your own error handling in the C<finally> block>. C<Try::Tiny> will |
7195fc08 |
327 | not do anything about handling possible errors coming from code located in these |
328 | blocks. |
329 | |
5f5e92c0 |
330 | Furthermore B<exceptions in C<finally> blocks are not trappable and are unable |
331 | to influence the execution of your program>. This is due to limitation of |
332 | C<DESTROY>-based scope guards, which C<finally> is implemented on top of. This |
333 | may change in a future version of Try::Tiny. |
334 | |
7195fc08 |
335 | In the same way C<catch()> blesses the code reference this subroutine does the same |
336 | except it bless them as C<Try::Tiny::Finally>. |
337 | |
3176feef |
338 | =back |
339 | |
340 | =head1 BACKGROUND |
341 | |
342 | There are a number of issues with C<eval>. |
343 | |
344 | =head2 Clobbering $@ |
345 | |
ad10a9e2 |
346 | When you run an C<eval> block and it succeeds, C<$@> will be cleared, potentially |
a717a876 |
347 | clobbering an error that is currently being caught. |
3176feef |
348 | |
1f7c5af6 |
349 | This causes action at a distance, clearing previous errors your caller may have |
350 | not yet handled. |
351 | |
352 | C<$@> must be properly localized before invoking C<eval> in order to avoid this |
353 | issue. |
3176feef |
354 | |
8e5b4441 |
355 | More specifically, C<$@> is clobbered at the beginning of the C<eval>, which |
511c05ca |
356 | also makes it impossible to capture the previous error before you die (for |
357 | instance when making exception objects with error stacks). |
358 | |
2b0d579d |
359 | For this reason C<try> will actually set C<$@> to its previous value (the one |
360 | available before entering the C<try> block) in the beginning of the C<eval> |
361 | block. |
511c05ca |
362 | |
3176feef |
363 | =head2 Localizing $@ silently masks errors |
364 | |
ad10a9e2 |
365 | Inside an C<eval> block, C<die> behaves sort of like: |
3176feef |
366 | |
8d2ee831 |
367 | sub die { |
368 | $@ = $_[0]; |
369 | return_undef_from_eval(); |
370 | } |
3176feef |
371 | |
372 | This means that if you were polite and localized C<$@> you can't die in that |
1f7c5af6 |
373 | scope, or your error will be discarded (printing "Something's wrong" instead). |
3176feef |
374 | |
375 | The workaround is very ugly: |
376 | |
8d2ee831 |
377 | my $error = do { |
378 | local $@; |
379 | eval { ... }; |
380 | $@; |
381 | }; |
3176feef |
382 | |
8d2ee831 |
383 | ... |
384 | die $error; |
3176feef |
385 | |
386 | =head2 $@ might not be a true value |
387 | |
388 | This code is wrong: |
389 | |
8d2ee831 |
390 | if ( $@ ) { |
391 | ... |
392 | } |
3176feef |
393 | |
1f7c5af6 |
394 | because due to the previous caveats it may have been unset. |
395 | |
1d64c1ad |
396 | C<$@> could also be an overloaded error object that evaluates to false, but |
397 | that's asking for trouble anyway. |
3176feef |
398 | |
399 | The classic failure mode is: |
400 | |
8d2ee831 |
401 | sub Object::DESTROY { |
402 | eval { ... } |
403 | } |
3176feef |
404 | |
8d2ee831 |
405 | eval { |
406 | my $obj = Object->new; |
3176feef |
407 | |
8d2ee831 |
408 | die "foo"; |
409 | }; |
3176feef |
410 | |
8d2ee831 |
411 | if ( $@ ) { |
3176feef |
412 | |
8d2ee831 |
413 | } |
3176feef |
414 | |
1f7c5af6 |
415 | In this case since C<Object::DESTROY> is not localizing C<$@> but still uses |
1d64c1ad |
416 | C<eval>, it will set C<$@> to C<"">. |
3176feef |
417 | |
1f7c5af6 |
418 | The destructor is called when the stack is unwound, after C<die> sets C<$@> to |
3176feef |
419 | C<"foo at Foo.pm line 42\n">, so by the time C<if ( $@ )> is evaluated it has |
1f7c5af6 |
420 | been cleared by C<eval> in the destructor. |
3176feef |
421 | |
1f7c5af6 |
422 | The workaround for this is even uglier than the previous ones. Even though we |
423 | can't save the value of C<$@> from code that doesn't localize, we can at least |
ad10a9e2 |
424 | be sure the C<eval> was aborted due to an error: |
3176feef |
425 | |
8d2ee831 |
426 | my $failed = not eval { |
427 | ... |
3176feef |
428 | |
8d2ee831 |
429 | return 1; |
430 | }; |
3176feef |
431 | |
1f7c5af6 |
432 | This is because an C<eval> that caught a C<die> will always return a false |
433 | value. |
3176feef |
434 | |
f9b91e2c |
435 | =head1 SHINY SYNTAX |
3176feef |
436 | |
1f7c5af6 |
437 | Using Perl 5.10 you can use L<perlsyn/"Switch statements">. |
3176feef |
438 | |
1f7c5af6 |
439 | The C<catch> block is invoked in a topicalizer context (like a C<given> block), |
440 | but note that you can't return a useful value from C<catch> using the C<when> |
27293e40 |
441 | blocks without an explicit C<return>. |
3176feef |
442 | |
443 | This is somewhat similar to Perl 6's C<CATCH> blocks. You can use it to |
444 | concisely match errors: |
445 | |
8d2ee831 |
446 | try { |
447 | require Foo; |
448 | } catch { |
449 | when (/^Can't locate .*?\.pm in \@INC/) { } # ignore |
450 | default { die $_ } |
451 | }; |
3176feef |
452 | |
453 | =head1 CAVEATS |
454 | |
455 | =over 4 |
456 | |
457 | =item * |
458 | |
013dca8f |
459 | C<@_> is not available within the C<try> block, so you need to copy your |
460 | arglist. In case you want to work with argument values directly via C<@_> |
461 | aliasing (i.e. allow C<$_[1] = "foo">), you need to pass C<@_> by reference: |
318cb1eb |
462 | |
8d2ee831 |
463 | sub foo { |
464 | my ( $self, @args ) = @_; |
465 | try { $self->bar(@args) } |
466 | } |
013dca8f |
467 | |
468 | or |
469 | |
8d2ee831 |
470 | sub bar_in_place { |
471 | my $self = shift; |
472 | my $args = \@_; |
473 | try { $_ = $self->bar($_) for @$args } |
474 | } |
318cb1eb |
475 | |
476 | =item * |
477 | |
478 | C<return> returns from the C<try> block, not from the parent sub (note that |
479 | this is also how C<eval> works, but not how L<TryCatch> works): |
480 | |
6651956b |
481 | sub parent_sub { |
8d2ee831 |
482 | try { |
483 | die; |
484 | } |
485 | catch { |
486 | return; |
487 | }; |
6651956b |
488 | |
8d2ee831 |
489 | say "this text WILL be displayed, even though an exception is thrown"; |
6651956b |
490 | } |
491 | |
492 | Instead, you should capture the return value: |
493 | |
494 | sub parent_sub { |
8d2ee831 |
495 | my $success = try { |
496 | die; |
497 | 1; |
86b8a58a |
498 | }; |
8d2ee831 |
499 | return unless $success; |
6651956b |
500 | |
8d2ee831 |
501 | say "This text WILL NEVER appear!"; |
6651956b |
502 | } |
318cb1eb |
503 | |
ad10a9e2 |
504 | Note that if you have a C<catch> block, it must return C<undef> for this to work, |
505 | since if a C<catch> block exists, its return value is returned in place of C<undef> |
6651956b |
506 | when an exception is thrown. |
318cb1eb |
507 | |
508 | =item * |
509 | |
1f7c5af6 |
510 | C<try> introduces another caller stack frame. L<Sub::Uplevel> is not used. L<Carp> |
c12e626f |
511 | will not report this when using full stack traces, though, because |
512 | C<%Carp::Internal> is used. This lack of magic is considered a feature. |
3176feef |
513 | |
514 | =item * |
515 | |
57c50f41 |
516 | The value of C<$_> in the C<catch> block is not guaranteed to be the value of |
517 | the exception thrown (C<$@>) in the C<try> block. There is no safe way to |
518 | ensure this, since C<eval> may be used unhygenically in destructors. The only |
519 | guarantee is that the C<catch> will be called if an exception is thrown. |
3176feef |
520 | |
a5cd5f73 |
521 | =item * |
522 | |
523 | The return value of the C<catch> block is not ignored, so if testing the result |
524 | of the expression for truth on success, be sure to return a false value from |
525 | the C<catch> block: |
526 | |
8d2ee831 |
527 | my $obj = try { |
528 | MightFail->new; |
529 | } catch { |
530 | ... |
a5cd5f73 |
531 | |
8d2ee831 |
532 | return; # avoid returning a true value; |
533 | }; |
a5cd5f73 |
534 | |
8d2ee831 |
535 | return unless $obj; |
a5cd5f73 |
536 | |
eaca95b7 |
537 | =item * |
538 | |
539 | C<$SIG{__DIE__}> is still in effect. |
540 | |
541 | Though it can be argued that C<$SIG{__DIE__}> should be disabled inside of |
542 | C<eval> blocks, since it isn't people have grown to rely on it. Therefore in |
543 | the interests of compatibility, C<try> does not disable C<$SIG{__DIE__}> for |
544 | the scope of the error throwing code. |
545 | |
cbfb5327 |
546 | =item * |
547 | |
548 | Lexical C<$_> may override the one set by C<catch>. |
549 | |
550 | For example Perl 5.10's C<given> form uses a lexical C<$_>, creating some |
551 | confusing behavior: |
552 | |
8d2ee831 |
553 | given ($foo) { |
554 | when (...) { |
555 | try { |
556 | ... |
557 | } catch { |
558 | warn $_; # will print $foo, not the error |
559 | warn $_[0]; # instead, get the error like this |
560 | } |
561 | } |
562 | } |
cbfb5327 |
563 | |
aaf0d61f |
564 | Note that this behavior was changed once again in L<Perl5 version 18 |
565 | |https://metacpan.org/module/perldelta#given-now-aliases-the-global-_>. |
566 | However, since the entirety of lexical C<$_> is now L<considired experimental |
567 | |https://metacpan.org/module/perldelta#Lexical-_-is-now-experimental>, it |
568 | is unclear whether the new version 18 behavior is final. |
569 | |
3176feef |
570 | =back |
571 | |
572 | =head1 SEE ALSO |
573 | |
574 | =over 4 |
575 | |
576 | =item L<TryCatch> |
577 | |
578 | Much more feature complete, more convenient semantics, but at the cost of |
579 | implementation complexity. |
580 | |
9bc603cb |
581 | =item L<autodie> |
582 | |
583 | Automatic error throwing for builtin functions and more. Also designed to |
584 | work well with C<given>/C<when>. |
585 | |
f8227e43 |
586 | =item L<Throwable> |
587 | |
588 | A lightweight role for rolling your own exception classes. |
589 | |
3176feef |
590 | =item L<Error> |
591 | |
592 | Exception object implementation with a C<try> statement. Does not localize |
593 | C<$@>. |
594 | |
595 | =item L<Exception::Class::TryCatch> |
596 | |
597 | Provides a C<catch> statement, but properly calling C<eval> is your |
598 | responsibility. |
599 | |
600 | The C<try> keyword pushes C<$@> onto an error stack, avoiding some of the |
1d64c1ad |
601 | issues with C<$@>, but you still need to localize to prevent clobbering. |
3176feef |
602 | |
603 | =back |
604 | |
faecd5a0 |
605 | =head1 LIGHTNING TALK |
606 | |
607 | I gave a lightning talk about this module, you can see the slides (Firefox |
608 | only): |
609 | |
9b3383e4 |
610 | L<http://web.archive.org/web/20100628040134/http://nothingmuch.woobling.org/talks/takahashi.xul> |
faecd5a0 |
611 | |
612 | Or read the source: |
613 | |
2245f1ae |
614 | L<http://web.archive.org/web/20100305133605/http://nothingmuch.woobling.org/talks/yapc_asia_2009/try_tiny.yml> |
faecd5a0 |
615 | |
3176feef |
616 | =head1 VERSION CONTROL |
617 | |
e5c5bdf1 |
618 | L<http://github.com/doy/try-tiny/> |
3176feef |
619 | |
3176feef |
620 | =cut |
621 | |