pry(main)> module Zultzen
pry(main)*   def hello
pry(main)*     puts "hello"
pry(main)*   end
pry(main)* end;
pry(main)> module Zultzen
pry(main)*   extend self
pry(main)* end
=> Zultzen
pry(main)> Zultzen.hello
hello
=> nil
pry(main)> class C; include Zultzen; end
=> C
pry(main)> C.new.hello
hello
=> nil
pry(main)>