I was wondering what would be the benefit of this? Especially if you benchmarked it against mod_perl.

Reading the article and the documentation of the CGIServlet-class: There are no benefits other than to be able to have a stand-alone tomcat execute CGI-programs (perl, bash, c++, ... it doesn't really matter); now that could be a real benefit. But you'd be still better off (performance-wise at least) using apache/mod_perl.