I have question about match_result.  How can I find out what was matched from the regular expression?  In the boost documentation, the example for regex_search does something similar to this...
regex needle("foo|bar");
string haystack("blah bar blah");
string::const_iterator start = haystack.begin();
string::const_iterator  end = haystack.end();
boost::match_results<string::const_iterator> what;
unsigned int flags = boost::match_default;

while(regex_search(start, end, what, expression, flags))
	// please output 'bar'
	string match(string(what[5].first, what[5].second) + std::string(what[6].first, what[6].second));
 	cout << "Found '" << match << "'\n";
	start = what[0].second;
	flags |= boost::match_prev_avail;
	flags |= boost::match_not_bob;

However, this is outputing nothing.  I also tried what.str(), but that gave me nothing too.

Thanks again,