$ su -
Password:
# cd /usr/bin
# mv perl perl-macosx
# ln -s /my/new/nice/perl
# ^D
[download]

This does not seem, to me, the right way to do things. You are replacing the factory-installed perl with your new/nice/perl. If any system level perl-based task expects something in its perl, and doesn't find it in your perl then there could be trouble.

However, that you don't trust marketplace binaries and roll your own instead is a very worthy sentiment. For now, I am trusting Activestate as a reliable starting point for my own excursions.