What about r'(^z*)|(q*)|(\w+)'? I could imagine that the first group
could match only at the start of the string, but if the second group
doesn't have that restriction then it could match the second time, and
only after that could the third match, if you see what I mean. (The
previous example had (^q*) so it couldn't match because the first group
has already matched at the start of the string and we've already
advanced beyond that, even though by no characters!)