permutations templates
  when <|=1> do [1] !
  otherwise
    n is $;
    expand templates
      p is $;
      1..$n -> templates
        k is $;
        [$p(..$k - 1)..., $n, $p($k..)...] !
      end !
    end expand
    $n - 1 -> # -> expand !
end permutations

alpha is ['ABCD'...];
[ $alpha::length -> permutations -> '$alpha($)...;' ] !