Fun with regex: if you're using the GCC C++ compiler and build you application with -D_GLIBCXX_DEBUG you can call the secret `std::regex::_M_dot(std::ostream&)`

Fun with regex: if you're using the GCC C++ compiler and build you application with -D_GLIBCXX_DEBUG you can call the secret `std::regex::_M_dot(std::ostream&)` member function and it will generate a graphviz illustration of the regex state machine. This was fantastically useful for developing my own regex engine.