sub getChecksum($) {
        my $in = shift;
        my $check = 0;
        $in =~ m/(?:(.)(?{$check += ord($1);}))*^/;
        return $check;
}

##</code><code>##

$in =~ m/(?:(.)(?{print "ASCII value of '$1' is: ".ord($1)."\n"; $check += ord($1);}))*^/;

##</code><code>##

getChecksum called with: 'foo'
ASCII value of 'f' is: 102
ASCII value of 'o' is: 111
ASCII value of 'o' is: 111
will return '324'

getChecksum called with: 'foo'
ASCII value of 'f' is: 102
ASCII value of 'o' is: 111
ASCII value of 'o' is: 111
will return '0'

##</code><code>##

        my @chars = split( //, $in );
        foreach my $char (@chars) {
                $check += ord($char);
        }