while (sysread(INDEX, $index_data, 65536)) {
  # so zip round it until we hit a byte with any bit
  # set to one
 for ($z = 0 ; $z < length ($index_data) ; $z++ ) {
    next unless ord(substr($index_data,$z,1));
    # so this byte contains something
    foreach (0..7) {
      if ( (2 ** $_) & ord(substr($index_data,$z,1)) ) {
        # this bit is ON
        # do stuff here
      }
    }
  }
}


##</code><code>##

    next unless ord(substr($index_data,$z,1));

##</code><code>##

    next unless substr($index_data,$z,1);