ruby-1.9.2-p0 > module M
ruby-1.9.2-p0 ?>  end
 => nil
ruby-1.9.2-p0 > class X < BasicObject
ruby-1.9.2-p0 ?>    include M
ruby-1.9.2-p0 ?>  end
NameError: uninitialized constant X::M
	from (irb):4:in `<class:X>'
	from (irb):3
	from /home/trans/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in `<main>'