Design decisions like “which framework to use” go far, far beyond considerations of CSS and beauty.   I’d simply suggest that you fully design and map-out your intended application before you subsequently choose which framework ... or for that matter, which programming language(s) if any(!) ... to use in constructing it.

(As great a language as Perl may be, never overlook the growing possibility that you do not, in fact, have to develop a new custom web-site at all in order to solve your business problem.)

The implementation strategy (CGI, Perl module, FastCGI, etc.) is likewise something that you can and should defer for a long time.   I know of several production web-sites used by rather big companies which are ... “good ol’ CGI.”

The definitive illustration of what can be done with CSS is, certainly, the CSS Zen Garden, which presents a wide variety of (perfectly nonsensical content ...) web site presentations from which you can freely pick and choose.   All of the variations of that content are devised using CSS, which is the key point that the site wishes to demonstrate.