reusing parts of a string in RE matches?

[John Salerno]

BartlebyScrivener wrote:
> I have to at least try :)
> 
> s = "abababababababab"
> 
> for x in range(len(s)):
> ... 	try:
> ... 		s.index("aba", x, x + 3)
> ... 	except ValueError:
> ... 		pass
> 
> rd
> 

yeah, looks like index() or find() can be used to do it instead of RE, 
but still, i'd like to know if there's a way you can write an RE 
expression to do it (and just an RE expression, without all the other 
for loops and extra nonsense...otherwise i might as well just use string 
methods)