** possible prefixes
   :PROPERTIES:
   :DATE:     2010-06-26
   :END:

| prefix   | remaining characters |
|----------+----------------------|
| ob-      |                    5 |
| org-b-   |                    2 |
| orgb-    |                    3 |
| org-bbl- |                    0 |
| bbl-     |                    4 |
| babel-   |                    2 |
#+TBLFM: $2='(sbe leftover (prefix $$1))

#+name: leftover
#+begin_src emacs-lisp :var prefix=""
  (-
   ;; length w/o .el
   (- 13 (length ".el"))
   ;; length of prefix
   (length prefix))
#+end_src