substring and regular expression

[borges2003xx at yahoo.it]

i have read
finding sublist
http://groups.google.it/group/comp.lang.python/browse_thread/thread/50b09a0aca285256/5156ada81fc9358a?hl=it#5156ada81fc9358a


the problem was in a string to find if we have two substring non
overlapping of lenght al least 4

it was done by
r=re.compile(r'(?P<seq>.{4,}).*(?P=seq)')

my knowhow on re is null
there is a way in re for ask if a substring is the reverse of the
otherone? First seq is second seq in reverse order

i appreciate all persons that can help me.
excuse my ignorance