So by now we all know that HTTP is the web protocol. Which is a bit sad, especially when you have more structured protocol for data interchange like Z39.50 which is used in libraries. But noways, it's much easier to get access to web interface than to Z39.50 server, so something had to be done.
A while ago, I was toying with idea of scraping web pages with MARC records and producing Z39.50 server using Net::Z3950::SimpleServer and WWW::Mechanize to turn HTTP interface back into Z39.50 server.
Source code is on github under name Biblio-Z3950 but it will probably require some tweaking if you want to support different sources than I do. But, code is simple enough and such change isn't hard, so have a look at it.