Just out of curiosity, I tried 'install POSIX'. I'm using 5.8.8, so it came back at me with

I'll build that only if you ask for something like
force install POSIX
or
install J/JE/JESSE/perl-5.12.1.tar.gz

If you didn't enter "force install", it shouldn't have installed it. You can check to see what perl your system is using with perl -v. If the install didn't delete your Policies, then the old perl should come up.