Splitting a stream of data on based on data change.

[Taylor R Hillegeist via Digitalmars-d-learn]

I was looking through the standard library for a good way to 
split a range into several ranges based on value changes in the 
stream:

AAAAAAABBBBBB
would be split on the AB transition into:
AAAAAAA BBBBBB
I just couldn't figure out an elegant way to do it? Any ideas?