You are right. In fact the procedure is as follows: The substr ``101101" is no problem, if stop here, match will successful. But the tailing `1' occurs, so we may imagine the working automata move to a state, which according to the regexp's outer most `)', and ready to repeat the whole regexp again. In this case, the answer is ``yes" only when there exists at least two ``1", but only one here.
BTW, the first string is matched exactly, according to your notion, it should be written as: _11_0_1011101 -- http://mail.python.org/mailman/listinfo/python-list
