** multiple evals for refs
   :PROPERTIES:
   :DATE:     2010-06-25
   :END:
#+begin_src emacs-lisp
  (setq counter 0)
#+end_src

#+name:
: 0

#+name: counter
#+begin_src emacs-lisp
  (setq counter (+ 1 counter))
  counter
#+end_src

#+begin_src emacs-lisp :var counter_val=counter
  counter_val
#+end_src

#+name:
: 3