$ cat 892293.pl use strict; use warnings; my $numTosses = 20; # Coin tosses per experiment (20 in this example) my $runs = (1<<$numTosses)-1; my @tailCnt; for (my $collection=0; $collection<1<<$numTosses; ++$collection) { my $tails=0; $tails += ($collection & 1<<$_) ? 1 : 0 for 0 .. $numTosses; $tailCnt[$tails]++; } print <