Select Code to Download

  substr( $q, 0, $k ) = reverse substr( $q, 0, $k );

  $q = reverse(substr($q, 0, $k)) . substr($q, $k);

sub fannkuch {
    use bytes;    # This makes it fractionally faster
...
    } while $index--;
    $maxflips;  # faster than an explicit return
}