karls-mac-mini:~ karl$ perlbrew list
  5.14.2threads
  perl-5.16.2
  perl-5.16.3
  perl-5.17.7
  perl-5.18.0
  perl-5.18.1
  perl-5.18.2
  perl-5.18.2threads
  perl-5.20.0
* perl-5.20.0threads