| 1 | warn "Legacy library @{[(caller(0))[6]]} will be removed from the Perl core distribution in the next major release. Please install it from the CPAN distribution Perl4::CoreLibs. It is being used at @{[(caller)[1]]}, line @{[(caller)[2]]}.\n"; |
| 2 | |
| 3 | # exceptions.pl |
| 4 | # tchrist@convex.com |
| 5 | # |
| 6 | # This library is no longer being maintained, and is included for backward |
| 7 | # compatibility with Perl 4 programs which may require it. |
| 8 | # This legacy library is deprecated and will be removed in a future |
| 9 | # release of perl. |
| 10 | # |
| 11 | # In particular, this should not be used as an example of modern Perl |
| 12 | # programming techniques. |
| 13 | |
| 14 | # Here's a little code I use for exception handling. It's really just |
| 15 | # glorfied eval/die. The way to use use it is when you might otherwise |
| 16 | # exit, use &throw to raise an exception. The first enclosing &catch |
| 17 | # handler looks at the exception and decides whether it can catch this kind |
| 18 | # (catch takes a list of regexps to catch), and if so, it returns the one it |
| 19 | # caught. If it *can't* catch it, then it will reraise the exception |
| 20 | # for someone else to possibly see, or to die otherwise. |
| 21 | # |
| 22 | # I use oddly named variables in order to make darn sure I don't conflict |
| 23 | # with my caller. I also hide in my own package, and eval the code in his. |
| 24 | # |
| 25 | # The EXCEPTION: prefix is so you can tell whether it's a user-raised |
| 26 | # exception or a perl-raised one (eval error). |
| 27 | # |
| 28 | # --tom |
| 29 | # |
| 30 | # examples: |
| 31 | # if (&catch('/$user_input/', 'regexp', 'syntax error') { |
| 32 | # warn "oops try again"; |
| 33 | # redo; |
| 34 | # } |
| 35 | # |
| 36 | # if ($error = &catch('&subroutine()')) { # catches anything |
| 37 | # |
| 38 | # &throw('bad input') if /^$/; |
| 39 | |
| 40 | sub catch { |
| 41 | package exception; |
| 42 | local($__code__, @__exceptions__) = @_; |
| 43 | local($__package__) = caller; |
| 44 | local($__exception__); |
| 45 | |
| 46 | eval "package $__package__; $__code__"; |
| 47 | if ($__exception__ = &'thrown) { |
| 48 | for (@__exceptions__) { |
| 49 | return $__exception__ if /$__exception__/; |
| 50 | } |
| 51 | &'throw($__exception__); |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | sub throw { |
| 56 | local($exception) = @_; |
| 57 | die "EXCEPTION: $exception\n"; |
| 58 | } |
| 59 | |
| 60 | sub thrown { |
| 61 | $@ =~ /^(EXCEPTION: )+(.+)/ && $2; |
| 62 | } |
| 63 | |
| 64 | 1; |