Display status when switch isn't given arguments.
Display status when switch isn't given arguments.

This also fixes a bug when switch isn't given any arguments.  When this
happens the ~/perl5/perlbrew/perls/current dir is linked to itself.
This is bad.

rafl/App-perlbrew,josl/App-perlbrew,rafl/App-perlbrew,Asuza/App-perlbrew,ptolemarch/App-perlbrew,dagolden/App-perlbrew,Asuza/App-perlbrew,rafl/App-perlbrew,calid/App-perlbrew,calid/App-perlbrew,josl/App-perlbrew,Asuza/App-perlbrew,ptolemarch/App-perlbrew,dagolden/App-perlbrew,josl/App-perlbrew,ptolemarch/App-perlbrew