...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::xpressive::by_ref — Embed a regex object by reference.
// In header: <boost/xpressive/regex_primitives.hpp> template<typename BidiIter> proto::terminal< reference_wrapper< basic_regex< BidiIter >const > >::type const by_ref(basic_regex< BidiIter > const & rex);