lib_mysqludf_preg is a library of mysql UDFs (user-defined-functions) that 
provide access to the PCRE (perl compatible-regular-expressions) library 
for pattern matching. The PCRE library is a set of functions that 
implement regular expression pattern matching using the same syntax and 
semantics as Perl 5. This syntax can often handle more complex expressions 
and capturing than standard regular expression implementations. For more 
information about PCRE, please see: http://www.pcre.org/

lib_mysqludf_preg is a useful performance optimization for those 
applications that are already performing these regular expression 
matches in a high level language (ie. PHP) on the client side. 
It is also helpful when there is a need to capture a parenthesized 
subexpression from a regular expression, or simply as a slight 
performance boost over the builtin RLIKE/REGEXP functions.

WWW: http://www.mysqludf.org/lib_mysqludf_preg/index.php