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Perl Exception handling
In perl is achieved with

    eval {
        die "Oops";
    };
    warn $@ . "\t...caught" if $@;

That prints out:

    Oops at - line 2.
            ...caught at - line 4.

In Perl 5 you can just write that as:

    eval {
        die "Oops";
    };
    warn if $@;

Similarly, "die if $@" will append "\t...propagated".

This also catches internal run-time errors:

        eval {
            $foo / 0;
        };

will produce a $@ "Illegal division by zero".

If you want to catch compile-time errors as well, then instead of

        eval {...};

you use an ordinary

        eval "...";

or, more likely,

        eval $string;

If you want a full-blown recovery block, you can write it like this:

    eval $your_ad_here;
    if ($@) {
        if    ($@ =~ /syntax error/)            { ... }
        elsif ($@ =~ /division by zero/)        { ... }
        elsif ($@ =~ /EOF in string/)           { ... }
        elsif ($@ =~ /Oops/)                    { ... }
        else                                    { die $@, "...propagated" }
    }

Note that the same exception handler can handle both compile-time and
run-time errors.  Escape codes are transmitted as strings rather than
as numbers, but you can always encode a number into a string if you
want.  Tom has implemented a set of catch/throw routines that do something
like you want.

By the way, I noticed you used "goto" in your implementation.  In Perl 4,
goto isn't powerful enough to do what you want.  It only works when the
target is not in a subroutine.  Perl 5's goto is a little more general.

But you've got the right idea.

Larry

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