a ip or other string, like "11.22.33.44" or "aa.bb.cc.dd". basically, I think it is very easy, (([\d\w]+)+\.)+[\d\w]+
but the problem is which group these submatches are in. not like ip, some string is consist of lots of words+separate
in pcre, I don't know how to extract it all words -- "aa bb cc dd ..."