Select Code to Download

        Rate regex  hash    gf
regex 1.94/s    --  -73%  -78%
hash  7.17/s  269%    --  -17%
gf    8.67/s  347%   21%    --

use strict;
use warnings;
...
sub gf {
  my @keep = grep {my %d; map {$d{$_}++} split ''; grep {$_ == 2} valu
+es %d} @data;
}