... /usr/local/bin/perl -> perl5.12.2
   ... /usr/local/bin/perl5.10.1.threads
   ... /usr/local/bin/perl5.10.1
   ... /usr/local/bin/perl5.12.2
   ... /usr/local/bin/perl5.16.0
   ...
   ... /usr/local/bin/perltest -> perl5.16.0