With a little bit of searching, I found the RFC on the Real-Time Streaming Protocol (RTSP) protocol here which describes the RTSP protocol as similar to HTTP/1.1, capable of being run over either TCP or UDP.

A subsequent search with CPAN revealed no modules matching the search string 'RTSP', suggesting there are no modules which have been written that support this protocol. However a little further Google searching found some interesting links here and here - At the end of all this however, it looks like you might have to resort to writing the RTSP client yourself based upon these references.