To be honest, it sounds to me if you are looking for information on using NPH (non-parsed header) scripts, using a content-type such as multipart/mixed or multipart/x-mixed-replace.

Perhaps these links may help:

• Google search of perlmonks.thepen.com for "NPH"
• Google search to the web for "nph headers"
• Google search to the web for "multipart/x-mixed-replace multipart/mixed"
• "An Exploration of Dynamic Documents," from Netscape
• Listing of MIME types, from a document at the University of Toronto

Hope that helps some. I'd be interested to hear what you find, if you're willing to report back on it.