gistfile1.txt

module Test
  module ClassMethods
    attr_accessor :var
    # Make everything in ClassMethods a class method on whatever includes this
    def self.included(klass)
      klass.extend ClassMethods
    end
  end
end

class Hello
  include Test
  @var = 3
end

Hello.var
# => NoMethodError: undefined method `var' for Hello:Class