** export blocks w/o languages
   :PROPERTIES:
   :DATE:     2010-07-09
   :END:
should raise an error

source
#+begin_src emacs-lisp
  ;; this is a comment
  (+ 1 1 1)
#+end_src

broken source
#+begin_src 
  (+ 2 2 2)
#+end_src

example
#+begin_example 
  this is exampled
#+end_example

#+begin_src ruby
  # this is the first
  [1, 2, 3, 4, 5].map{|r| r+1}
#+end_src