Added>> I forgot to mention this but the other responses gave you the right information. <<

There's an example of something spectacularly wrong in Re: Stealing lexicals - best practice suggestions which happens to be exactly what you're looking for. It steals private my() variables out of another package and turns them into globals. The wicked witch of the west's evil monkey minions will cart you off if you actually do this.

All this proves is that it is possible to do what you asked but only through wrong doing.