// In header: <boost/xpressive/regex_actions.hpp>

struct unwrap_reference {
  // member classes/structs/unions
  template<typename Sig> 
  struct result {
  };
  template<typename This, typename Ref> 
  struct result<This(Ref &)> {
    // types
    typedef boost::unwrap_reference< Ref >::type & type;
  };
  template<typename This, typename Ref> 
  struct result<This(Ref)> {
    // types
    typedef boost::unwrap_reference< Ref >::type & type;
  };
  // public member functions
  template<typename T> T & operator()(boost::reference_wrapper< T >) const;
};