gistfile1.txt

module Foo
  def self.included(base)
    class << base
      attr_accessor :bar
    end
    base.instance_eval do
      @bar = "pig"
    end
  end
end


class Baz
  include Foo
end

Baz.bar
Baz.instance_eval do
  @bar = "cow"
end
Baz.bar