Enumerable#repeated_permutation

The computer I'm using doesn't have a version of Ruby which supports Enumerable#repeated_permutations.

The following snippet was copied from [http://pastebin.com/BnHnExBQ](http://pastebin.com/BnHnExBQ).

    module Enumerable
      def repeated_permutation(size, &blk)
        f = proc do |memo, &blk|
          if memo.size == size
            blk.call memo
          else
            self.each do |i|
              f.call memo + [i], &blk
            end
          end
        end

        if block_given?
          f.call [], &blk
        else
          Enumerator.new(f, :call, [])
        end
      end
    end

enumerable repeated_permutation