I don't know for sure what this is but, it looks similar to a MS "__VIEWSTATE". If that is what it is, then essentially this is some internal server info that the server asks the client to save. This reduces server storage space/db access at the expense of client<->server communication bandwidth. The client acts like extended storage of the server.

Its been awhile since I wrote an LWP client to talk to an MS ASP server that required this, but what happens is that the server sends you a bunch of gibberish that you save and then re-send on the next request. The server then supplies "new" gibberish that you save again for the next request.

What is that "gibberish", who knows? The client does nothing at all with it. The client just functions as temporary storage for this stuff.

Don't know what is happening here, but this is one of the possibilities. And if so, there is no way that you will ever figure out what this bunch of gibberish means. It is server/application specific "state-of-the-connection" information.