This module provides a simple function to parse and extract search
engine query strings.  It was designed and tested having Apache referrer
logs in mind.  It can be used for a wide number of purposes, including
tracking down what keywords people use on popular search engines before
they land on a site.  It makes use of URI::split to extract the string
and URI::Escape to un-escape the encoded characters in it.  Although a
number of existing modules and scripts exist for this purpose, the
majority of them are either outdated using obsolete search strings
associated with each engine.

WWW: http://search.cpan.org/dist/URI-ParseSearchString/