That's one of the standard techniques described in wikipedia, but it's not 100% cause it relies on convention.

And I really prefer lexicals cause there scope is controllable, and I don't need to localize the variables in recursive calls.

Furthermore a full qualified $Some::Really::Long::Package::foo++ can be so cumbersome that people would like using a placeholder again... maybe $<PCKG>::foo .

A lexical variation of this package idea would be just one hash $<MyHash>{foo} and to only assure that this hash's name is unique.

But I admit that in the future I might need to support "safe" package variables for this project too.