For just 2 perls, switching a symbolic link would be easy. In my experience, Perl installs itself to wherever with a version string attached to the binary, like /usr/bin/perl5.14.1 or /usr/local/bin/perl5.16.1. So all you need to do is make a symbolic link called /usr/local/bin/perl to point to either of those actual binaries. With more than 2, perlbrew is probably wise. On almost all systems, /usr/local/bin is searched before /usr/bin in the PATH, so you just need to make your shebang line #!/usr/local/bin/perl and any use of "perl" on its own will follow the symbolic link found in the PATH.