Actually, thinking about this a bit more, if you browse the files in the release there is a "._*" file for every normal file and they are all 82 bytes. I suspect these are some sort of MacOS specific resource fork / hidden files that made it into the release by mistake (as an artifact of whatever mechanism was used to copy/bundle up the tgz) and ExtUtils::MakeMaker seems to be making some sort of assumption about the "._Makefile.PL"

have you tried just removing the "._*" files from the distribution after you unpack it (and before running perl Makefile.PL) to see if that solves your problem?