while ( $lo <= $hi ) {
        my $try = int( ( $lo + $hi ) / 2 );
        if ( $array[ $try ] lt $word ) {
            $lo = $try + 1; # without increment there will be
                            # a dead loop in the 4th case,
                            # see the note at the bottem
        }
        elsif ( $array[ $try ] gt $word ) {
            $hi = $try - 1;
        }
        else {
            return $try
        }
    }