I'm glad to see that I'm not the only one who is extremely annoyed by Module::Build's disregard towards PREFIX . The Module::Build documentation says:
Note that this is different from how MakeMaker's PREFIX parameter works. PREFIX tries to create a mini-replica of a site-style installation under the directory you specify, which is not always possible (and the results are not always pretty in this case).
Ok, so they decided not to support PREFIX because they don't think it's pretty? I don't know what they mean when they say "it is not always possible". PREFIX has always worked for me (with ExtUtils::MakeMaker), and I assume that other people who choose to use it also found that it works for them.