Filter file name with Boost regular expression

The story of the use case is like this; given a file name having the pattern, dummyx.txt, where x is a running number, how could I effectively filter out those doesn't match with this pattern? My initial answer would be this:

set<wstring> files = ... // assuming a list of file name are return and kept in the variable files

set<wstring>::iterator it;

for( it=list.begin(); it != list.end(); it++ ) {
    if ((*it).find(L"dummy.txt") != string::npos) {
        /***** proceed with the flow *****/
    }
}

I just feel that this piece is so rough. Instead of comparing the file name using wildcard search, I start to think of a more elegant way to get this done. So the first idea pops up in my mind is to use regular expression, here come to the second revision of the piece:

boost::regex expr("([\\:/\\\\\\w]+)?dummy(\\d{1,3})(\\.txt)$");
set<wstring>::iterator it;

for( it=list.begin(); it != list.end(); it++ ) {
    string s((*it).begin(), (*it).end());
    if (boost::regex_match(s, expr)) {
        /***** proceed with the flow *****/
    }
}

Much better? At least the code look much more elegant than the previous piece. Not only that it will filter out those doesn't match with the pattern, it will also filter out the name with only dummy in the file name.