** eval for side effect on export
   :PROPERTIES:
   :DATE:     2010-08-26
   :END:
- one plus one
  #+name: one-plus-one
  #+begin_src emacs-lisp :exports none :results silent
    (+ 1 1)
  #+end_src
- plus one is
  #+begin_src emacs-lisp :var two=one-plus-one :exports both
    (+ 1 two)
  #+end_src