Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Global upper

boost::xpressive::upper — Matches an upper-case character.

unspecified upper;

The regex traits are used to determine which characters are upper-case. To match any character that is not upper-case, use ~upper.