my $bal;
$bal = qr /[(]((?:(?>[^()]+)|(??{$bal}))*)[)]/;

my $func = qr /([a-zA-Z]\w*)\s*$bal/;

while (<>) {
    while (/$func/g) {
        print "Name: $1; arguments: $2\n"     
    }
}

##</code><code>##

    foo (bar ())

##</code><code>##

    foo ("(");
    bar (")))");

##</code><code>##

    /* This works (really!) */