Like others have said before me it really depends on what you want to measure. If you have control of the network (meaning you are directly connected to the sever) then holli's advice would probably be the best since it would take into account the server overhead time which should be much better under mod_perl.

If you don't have control over the network, I would say running something like holli's script on the same box would be better than trying it over a messy network. And Javascript would not be able to give you an accurate benchmark of anything other than how long the page takes to render which is not what you are asking (I believe).