Feature request: support multiple local::libs

[Klortho]

I don't think Python's virtualenv does this -- I don't think you can have multiple virtualenvs active at the same time. But Perl's local::lib certainly does, and it would be really handy if this tool could support it.

In a quick test I just did, I was able to create and activate multiple perl virtualenvs, but ran into a problem when I tried to deactivate. The first deactivate worked, but then, when I tried to deactivate again, the alias had been undefined.