#include <iostream>
#include <boost/regex.hpp>

// link with -lboost_regex

int main(int argc, char** argv)
{
  boost::regex reg("^B");

  std::string src = "BOUNCE BOUNCE BOUNCE";

  std::cout << src << std::endl;

  std::string out = boost::regex_replace(src, reg, "P");

  std::cout << out << std::endl;

  return 0;
}