Someone

  namespace qi = boost::spirit::qi;
  using enc::alnum;

  bool r = phrase_parse(
                        first,                          /*< start iterator >*/
                        last,                           /*< end iterator >*/
                        alnum[ boost::phoenix::ref(std::cout) << "Read: " << qi::_1 << std::endl ],       /*< the parser >*/
                        space                           /*< the skip-parser >*/
                        );