templates lexicalPermutations2
  def N: $;
  [[1]] -> #
  when <[<[]($N)>]> do $... !
  otherwise
    def tails: $;
    [1..$tails(1)::length+1 -> \(
      def first: $;
      $tails... -> [$first, $... -> \(when <$first..> do $+1! otherwise $!\)] !
    \)] -> #
end lexicalPermutations2

def alpha: ['ABCD'...];
[ $alpha::length -> lexicalPermutations2 -> '$alpha($)...;' ] -> !OUT::write