Parallele Ajax, Parameters To Response Handler?

i'm new to ajax. simple request no problem - but it seems when I set
the response handler function, I can only pass the function name and
not give parameters, so I have a problem when starting e.g. 5 ajax
requests parallele. how to do that correctly? for one case, where I
used *different* resp. handlers, I solved the problem by global
variables - but now I have a loop of e.g. 20 calls to the *same*
r.handler and I don*t know how to tell the function *which* request of
the 20 to use. I expect the solution to be simple but how..