does "ee" really appear only 5 times in "eeeeeeeeee" ??
I would say no, and here's my reasoning:
Initial string "eeeeeeeeee"
First occurance of ee would be the first two e's (ie;$left(string,2))
Second occurance would be the 2nd & 3rd letters, since I don't see anything that says that the second e from the first occurance shouldn't be allowed as the first e in the second occurance.
Therefore, in my opinion, I agree that this could be considered to be a bug.