I think you mean you want a (let's assume) perl app to stress test some networking product or other by pretending to be many client machines, and that for the sake of realism the requests it generates should appear to come from several IP addresses. Let's also assume that you're not writing a DoS machine.

The best place to start would probably be mstone, part of the mozilla project and very likely to handle the protocol you want. Not very perly, though.

Or you could, if you really want, roll your own using LWP or some set of socket libraries, in which case merlyn has inevitably written a couple of columns that will help.

as far as the IP address part of the question goes, I don't think it can be answered without knowing more about what you intend. IP spoofing is no good because you will presumably need to assess the server response. Your best bet is probably to set up the XP box to assign several IP addresses to a single network connection, which is easy enough, then spend some time with perlipc, get friendly with your sockets and then use IO::Socket or one of its offspring to do the work.