I got rid of the mac OS that came with my PPC box and replaced it with Debian Wheezy.
After Wheezy had been installed, there were a few things I had to apt-get in order to acquire the full toolchain needed to build perl.
Once that was all done, building perl was quite trivial - just run Configure with whatever args you choose, followed by 'make', 'make test' and 'make install'.

I didn't even try to build perl on that machine while the mac system was in place - so I probably have no experience that can help you in that regard.

Cheers,
Rob