This example is taken from: http://rt.cpan.org/Public/Bug/Display.html?id=20879

---     ---     ---
Level 5     8 | A | 9 | B | A | C |    (More General)
---     ---     ---       V
   \     |     /          |
    \    |    /           |
     \   |   /            |
      \  |  /             |
        ---               |
Level 4             7 | D |              |
        ---               |
       /   \              |
      /     \             |
   ---       ---          |
Level 3        4 | G |   6 | E |         |
   ---       ---          |
    |         |           |
    |         |           |
   ---       ---          |
Level 2        3 | H |   5 | F |         |
   ---       ---          |
       \   /  |           |
        \ /   |           |
         \    |           |
        / \   |           |
       /   \  |           |
   ---       ---          |
Level 1        1 | J |   2 | I |         |
   ---       ---          |
     \       /            |
      \     /             |
        ---               v
Level 0             0 | K |            (More Specialized)
        ---

0123456789A KJIHGFEDABC