c++11 regex and version stripping

regex_version_example.cc

#include <regex>
#include <iostream>
#include <string>

using namespace std;

int main() {
        string input;
        regex integer("([[:digit:]]+.[[:digit:]]+.[[:digit:]]+)(-.*)?");
        smatch matches;
        while (true) {
                cout << "Version please." << endl;
                cin >> input;
                if (!cin || input == "q") return 0;
                if (regex_search(input, matches, integer)) {
                        cout << "Version: " << matches[0].str() << endl;
                        cout << "Stripped version: " << matches[1].str() << endl;
                } else {
                        cout << "That's not a version." << endl;
                }
        }
}