There is a bit of documentation with the source code:
I've found some good info in the slides from a YAPC 2009 talk : perpal-tutorial. It's at slideshare.net, so it requires flash or a login.
Ok, now that I've read all that, how do I set it up as a simple proxy/balancer between my internal service and n (small) external hosts, with connection pooling, persistent connections from perlbal to the external hosts?
My internal service will need to quickly send a request to each of the remote servers and then aggregate/modify the collective response. My internal service won't wait very long for the responses from the n hosts => slow responses (<~200ms?) will just be dropped from the algorithm.
... investigation continues.