$count{$_}++ for $string =~ /../g;

[download]

Update: With the clarifications of the problem statement: 

while( @strings ) {
    my( $x, $y )= splice @strings, 0, 2;
    my %count;
    while(  $x =~ /(.)/g  ) {
        my $x1= $1;
        $y =~ /(.)/g
            or  die "...";
        $count{ $x1.$1 }++;
        # Or replace all of the above with:
        #$count{ "$1" . ( $y =~ /(.)/g ? "$1" : '' ) }++;
    }
    print join " ", %count, $/;
}

[download]

with the (simple) cleaning up of the output left as an excercise.

- tye        

In reply to Re: Speeding permutation counting (/../g) by tye
in thread Speeding permutation counting by albert

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