Insertion sort in Ruby

gistfile1.rb

class Array
  def insertion_sort
    inject([]) { |mem, var| mem.insert_with_order(var) }
  end
  def insert_with_order(var)
    pos = find_index { |v| var <= v } || length
    insert(pos, var)
  end
end

ar = [4,2,1,6,7,34,11,9]
p ar.insertion_sort
# [1, 2, 4, 6, 7, 9, 11, 34]