sub fisher_yates_shuffle {
    my $array = shift;
    my $i;
    my $mmCount = @$array;
    datePrint "Executing Fisher-Yates shuffle up to $mmCount times...\n";
    my $mmStatus = 10000;
    for ($i = @$array; --$i; ) {
        if (--$mmStatus == 0) {
           datePrint "$i more to go...\n";
           $mmStatus = 1000000;
        }
        my $j = int rand ($i+1);
        next if $i == $j;
        @$array[$i,$j] = @$array[$j,$i];
    }
}