CL-Portable Perl-compatible Regular Expressions---CL-PPCRE (The Universe Known as LISP)

“Portable Perl-compatible regular expressions for Common Lisp”

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

It is compatible with Perl (especially when used in conjunction with cl-interpol, to allow compatible parsing of regexp strings).
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.

To use it, load it through quicklisp:

(ql:quickload :cl-ppcre)