The buggy code

mistake.pl

multi binary-search ($x, @array --> Int) {
    binary_search $x, @array, 0, end @array;
}
multi binary-search ($x, @array, Int $low, Int $high --> Int) {
    return Int unless $low before $high;
    my Int $middle = ($low + $high) div 2;

    # In Perl 6, cmp is DWIM comparison, unlike Perl 5
    given $x cmp @array[$middle] {
        when Increase { binary_search $x, @array, $low,        $middle - 1 }
        when Decrease { binary_search $x, @array, $middle + 1, $high       }
        when Same     { $middle }
    }
}
say binary-search 42, [1, 5, 7, 23, 33, 37, 39, 41, 42, 45, 56, 72];