That's why I'm asking - I'm not sure how I intend to do it :)

I want to do this because I do not want older code (read: default install location) to be calling functions in a newer codebase just because something called a function in the new codebase (and thereby required the new modules, replacing the symbols that existed).

I.e.

My::Package::foo();
...
NEW::My::Package::foo();
...
My::Package::foo();  # this one I want to use the old codebase always,
+ even if someone called the NEW:: version at some point.
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