The package provides regular expression testing, extraction of submatches, splitting, and replacement, all acting on token lists. The syntax of regular expressions is mostly a subset of the PCRE syntax (and is very close to Posix), with some additions arising from the fact that TeX manipulates tokens rather than characters.

For performance reasons, only a limited set of features are implemented. Notably, back-references are not supported.

The package is currently distributed as part of the LaTeX3 l3experimental bundle.

The author is The LaTeX Team. The package is Copyright © 2011-2012 The LaTeX3 Project.