So other than providing a clean API -- for your first point, it could also help to prevent those hard to spot bugs when you inherit (or use a role) with the same name as that utility function you imported as a one-off. I'm thinking of action at a distance.
I'm also not great at remembering which keywords are reserved in which problem domains.
Just tried your code and the second example is insidious. I can see the error thrown when I remove namespace::autoclean from your example, but when I do it in a module and run the test it passes, no error. For me, intermittent errors are the worst. I think ns::ac just became part of my boilerplate.
Sometimes I can think of 6 impossible LDAP attributes before breakfast.
Mojoconf was great!