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# exceptions.pl # tchrist@convex.com # # This library is no longer being maintained, and is included for backward # compatibility with Perl 4 programs which may require it. # # In particular, this should not be used as an example of modern Perl # programming techniques. # # # Here's a little code I use for exception handling. It's really just # glorfied eval/die. The way to use use it is when you might otherwise # exit, use &throw to raise an exception. The first enclosing &catch # handler looks at the exception and decides whether it can catch this kind # (catch takes a list of regexps to catch), and if so, it returns the one it # caught. If it *can't* catch it, then it will reraise the exception # for someone else to possibly see, or to die otherwise. # # I use oddly named variables in order to make darn sure I don't conflict # with my caller. I also hide in my own package, and eval the code in his. # # The EXCEPTION: prefix is so you can tell whether it's a user-raised # exception or a perl-raised one (eval error). # # --tom # # examples: # if (&catch('/$user_input/', 'regexp', 'syntax error') { # warn "oops try again"; # redo; # } # # if ($error = &catch('&subroutine()')) { # catches anything # # &throw('bad input') if /^$/;
sub catch { package exception; local($__code__, @__exceptions__) = @_; local($__package__) = caller; local($__exception__);
eval "package $__package__; $__code__"; if ($__exception__ = &'thrown) { for (@__exceptions__) { return $__exception__ if /$__exception__/; } &'throw($__exception__); } }
sub throw { local($exception) = @_; die "EXCEPTION: $exception\n"; }
sub thrown { $@ =~ /^(EXCEPTION: )+(.+)/ && $2; }
1;
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