my %common;
    @common{@common} = (1) x @common;

##</code><code>##

    Benchmark: timing 1000 iterations of Odud, btrott, visnu...
        Odud:   4 secs ( 3.55 usr  0.00 sys =  3.55 cpu)
        btrott: 2 secs ( 2.27 usr  0.00 sys =  2.27 cpu)
        visnu:  4 secs ( 3.98 usr  0.00 sys =  3.98 cpu)