Thx for your reply ikegami,

I have since restored my original xubuntu 13.10 from backups -- I was getting a little bit desperate. The restored perlbrew installation is working now.

This is not much of a solution, though, as I need to upgrade my xubuntu to 14.04.

I think I need to backup my perlbrew install independent of my general backup. And then install the perlbrew modules separately in another system. I was reading some literature regarding that. But I'd definitely appreciate your input on that. I am beginning to feel that I am out of my depths here.

I still would like to understand how the upgrade broke the perlbrew install. So I will try to re-create the problem as soon as I can get perlbrew installed properly in an upgraded xubuntu.