regex: flag for "global" search?

I'm trying to capture the sub-expressions in a fqdn (e.g., one.two.three.com.). One piece of Perl-speak for the expression is: "/ (\w+)\./g". I've been using boost_search and trying variations on "(?: (\\w+)\\.)+" but I can't seem to get all the sub-expressions into the match_results. There's got to be a flag I've been overlooking. Any suggestion will be appreciated. TIA