gistfile1.rbx

module Foo
  module_function
  def make_foo_mod
    foo_closure = "omgwtfBBQ"
    Module.new do
      def foo_class_var; foo_closure end
      def foo_class_var= stuff; foo_closure = stuff end
    end
  end
end

class Alpha
  include Foo.make_foo_mod
end

class Beta
  include Foo.make_foo_mod
end