Fixed with a !!, thanks.

No, that didn't do it. I'm getting undef where a true return is expected...

Ah, I see. You had -1 ==, I think you meant -1 !=...

    buk4 => sub {
        ( -1 != index $_[0], chop $_[ 1 ] ) || return for 1 .. length 
+$_[ 1 ];
        1;
    },
[download]

Once I made that change, it passes all the tests (which are now updated to check truth values) and it does win the speed crown by a 1% (on Short) to 11% (on LongLong) margin over buk3 (on perl 5.8.4 - I don't have my mac handy).