CL-PPCRE is a portable regular expression library for Common Lisp which has the
following features:

- It is compatible with Perl.
- It is pretty fast.
- It is portable between ANSI-compliant Common Lisp implementations.
- It is thread-safe.
- In addition to specifying regular expressions as strings like in Perl you can
  also use S-expressions.
- It comes with a BSD-style license so you can basically do with it whatever
  you want.

CL-PPCRE-UNICODE is CL-PPCRE with unicode extensions.