my ($sum, $rolls) = (0,0);
for my $hi (1..6) {
  for my $mid (1..$hi) {
    for my $low (1..$mid) {
      # The drop value can be anything from 1..$low
      $sum += ($hi + $mid + $low) * $low;
      $rolls += $low;
    }
  }
}
printf "The average value is %g\n", $sum/$rolls;