Boost regex groups

I have looked as much as I could on the internet and boost documentation for sub-group matches and can't find anything on the matter. Basically say I have a simple expression like this: "(\\d{5,5})-(\\d{3,3})" And want to match it against the following string: "12345-678" In every implementation of regex I've seen, you could extract the actual number 12345, and 678 by extracting them as groups in a very simple and straight forward manner. Specifically this could be done in Java and Python. Was hoping there is also a simple way to do this in Boost.RegEx. Thanks.