module ModuleLevelInheritableAttributes::ClassMethods

def inherited(subclass)
  @mattr_inheritable_attrs.each do |inheritable_attribute|
    instance_var = "@#{inheritable_attribute}" 
    subclass.instance_variable_set(instance_var, instance_variable_get(instance_var))
  end
end

def mattr_inheritable(*args)
  @mattr_inheritable_attrs ||= [:mattr_inheritable_attrs]
  @mattr_inheritable_attrs += args
  args.each do |arg|
    module_eval %(
      class << self; attr_accessor :#{arg} end
    )
  end
  @mattr_inheritable_attrs
end