ruby acrobatics

main.rb

#recursive lexicographic permutations

def perm(str)
  res = []
  if str.length <= 1
    return res << str
  else
    t = []
    str.each_char do |chr|
      t += perm(str.delete(chr))
      t.each do |permutation| 
        res << chr + permutation unless permutation.include?(chr)
      end
    end
  end
  return res
end