Select Code to Download

             Rate     pure stirling     memo
pure      15037/s       --     -89%     -94%
stirling 139183/s     826%       --     -48%
memo     267957/s    1682%      93%       --

#!/usr/bin/perl -w
use strict;
...
    return ( $fact[ $n ] or $fact[ $n ] = $n * factorial_memo( $n - 1 
+) );
  }
}