5.18.2, which is shipped with OS X 10.10
I tried to install the latest as shown above, but this happened:
rnelson@boxer ~ $ perlbrew install 5.21.8 && perlbrew switch 5.21.8
Fetching perl 5.21.8 as /Users/rnelson/perl5/perlbrew/dists/perl-5.21.8.tar.bz2
sh: tar: command not found
Failed to extract /Users/rnelson/perl5/perlbrew/dists/perl-5.21.8.tar.bz2 at /Users/rnelson/perl5/perlbrew/bin/perlbrew line 963.
rnelson@boxer ~ $ which tar
-bash: which: command not found
rnelson@boxer ~ $
It took /usr/bin out of $PATH and then broke when tar (which lives at /usr/bin/tar) wasn't found.