pseudo_refinements.rb

module Refinements
  def self.included core
    core.send :include, Refinements.const_get(core.to_s)
  end

  module String
    def ^ other
      chars.zip(other.chars.cycle).map { |a, b| (a.ord ^ b.ord).chr }.join
    end
  end
end

class String
  include Refinements
end