# exceptions.pl# tchrist@convex.com# # 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;