karls-mac-mini:uagent 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
  perl-5.22.1-threads
* perl-5.24.1threads

karls-mac-mini:uagent karl$ perlbrew switch perl-5.18.0
karl-mac-mini:uagent 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
  perl-5.22.1-threads
  perl-5.24.1threads