[REBOL] Extracting a series of duplicates

[David]

I can't seem to find the right combination of functions to do this: Create a 
series containing the values that are repeated in another series. For example, 
if the first series is [1 2 2 3 4 5 5 5 6], the new series should be [2 5]. Any 
hints or solutions are appreciated.
-- 
To unsubscribe from the list, just send an email to 
lists at rebol.com with unsubscribe as the subject.