[Boost-users] [regex] why partial match / early break ?

Hi, why is this regex const string sRe = "((([a-zA-Z]|([a-zA-Z][a-zA-Z0-9\\-]))+[a-zA-Z0-9])\\.)+" "((([a-zA-Z]|([a-zA-Z][a-zA-Z0-9\\-]))+[a-zA-Z0-9]))"; not matching this string wholly? "a1a.a2a.a3a.a4aaaa" It rather matches only this part: "a1a.a2a.a3a.a4" What's the problem here? (I know I can append a delimiter to solve the problem, but I think the regex should've match it wholly, shouldn't it?)