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Comparing Guard/Guard.pm (file contents):
Revision 1.13 by root, Sat Dec 13 19:14:58 2008 UTC vs.
Revision 1.17 by root, Fri Dec 26 13:04:04 2008 UTC

… …
10 # to go back to "/" no matter how myfun exits: 10 # to go back to "/" no matter how myfun exits:
11 sub myfun { 11 sub myfun {
12 scope_guard { chdir "/" }; 12 scope_guard { chdir "/" };
13 chdir "/etc"; 13 chdir "/etc";
14 14
15 call_function_that_might_die_or_other_fun_stuff; 15 code_that_might_die_or_does_other_fun_stuff;
16 } 16 }
17 17
18=head1 DESCRIPTION 18=head1 DESCRIPTION
19 19
20This module implements so-called "guards". A guard is something (usually 20This module implements so-called "guards". A guard is something (usually
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37package Guard; 37package Guard;
38 38
39no warnings; 39no warnings;
40 40
41BEGIN { 41BEGIN {
42 $VERSION = '0.5'; 42 $VERSION = '1.0';
43 @ISA = qw(Exporter); 43 @ISA = qw(Exporter);
44 @EXPORT = qw(guard scope_guard); 44 @EXPORT = qw(guard scope_guard);
45 45
46 require Exporter; 46 require Exporter;
47 47
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162all, they are usually used to clean up after such exceptions. However, if 162all, they are usually used to clean up after such exceptions. However, if
163something truly exceptional is happening, a guard block should be allowed 163something truly exceptional is happening, a guard block should be allowed
164to die. Also, programming errors are a large source of exceptions, and the 164to die. Also, programming errors are a large source of exceptions, and the
165programmer certainly wants to know about those. 165programmer certainly wants to know about those.
166 166
167Since in most cases, the block executing when the guard gets executes does 167Since in most cases, the block executing when the guard gets executed does
168not know or does not care about the guard blocks, it makes little sense to 168not know or does not care about the guard blocks, it makes little sense to
169let containing code handle the exception. 169let containing code handle the exception.
170 170
171Therefore, whenever a guard block throws an exception, it will be caught, 171Therefore, whenever a guard block throws an exception, it will be caught,
172and this module will call the code reference stored in C<$Guard::DIED> 172followed by calling the code reference stored in C<$Guard::DIED> (with
173(with C<$@> set to the actual exception), which is similar to how most 173C<$@> set to the actual exception), which is similar to how most event
174event loops handle this case. 174loops handle this case.
175 175
176The default for C<$Guard::DIED> is to call C<warn "$@">. 176The default for C<$Guard::DIED> is to call C<warn "$@">.
177 177
178The C<$@> variable will be restored to its value before the guard call in 178The C<$@> variable will be restored to its value before the guard call in
179all cases, so guards will not disturb C<$@> in any way. 179all cases, so guards will not disturb C<$@> in any way.
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189=head1 THANKS 189=head1 THANKS
190 190
191Thanks to Marco Maisenhelder, who reminded me of the C<$Guard::DIED> 191Thanks to Marco Maisenhelder, who reminded me of the C<$Guard::DIED>
192solution to the problem of exceptions. 192solution to the problem of exceptions.
193 193
194=head1 SEE ALSO
195
196L<Scope::Guard> and L<Sub::ScopeFinalizer>, which actually implement
197dynamic, not scoped guards, and have a lot higher CPU, memory and typing
198overhead.
199
200L<Hook::Scope>, which has apparently never been finished and corrupts
201memory when used.
202
194=cut 203=cut
195 204

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