Ever wanted Array#penultimate? How about Array#penpenultimate

gistfile1.rb

class Array
  def method_missing(method_sym, *arguments, &block)
    if method_sym.to_s =~ /^((pen)+)ultimate$/
     pen_index = 1 + ($1.length/3)
     self[-pen_index]
    else
      super
    end
  end
end