Using boost's replace_all_regex_copy

#include <iostream>
#include <string>
#include <algorithm>
#include "boost/algorithm/string/regex.hpp"

using namespace std;

int main(void) {
    string orig_str="FUBAR";
    boost::regex re("UBA");
    std::string replacement="ooba";
    string result = boost::algorithm::replace_all_regex_copy(
        orig_str,re,replacement);
    cout << result << endl;
    return 0;
}

Yields:

FoobaR