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As the thread here on PM and the two CPAN modules (written by notable Perl people) suggests, this is not as easy as it looks. I think the best way to get it right each time is to find an approach that always acts as "expected", and then put it in a module. I trust a module to be more consistent than me when faced with a repeated problem. :-)
Regarding your suggestions; it fails to behave like I would expect when it is inherited (and upon object destruction, but to be fair you do not have a constructor).
In my solution outlined in the root node I handle it by moving the logic that generates the autoloaded subroutine reference to a common routine that both AUTOLOAD and can use. Then I see if UNIVERSAL::can returns anything. If it does it means that AUTOLOAD will not be invoked for $o->bar, so the return value of UNIVERSAL::can should be used instead. (This of course assumes that UNIVERSAL::can is not overloaded to do something else.)
The remaining logic in the root node is to handle when you use AUTOLOAD in a child class and the parent class also uses AUTOLOAD. This is even rarer, but it is still possible. As you say, it is important to trust a module to handle all edge cases so that you don't end up spending your evening debugging due to the module.
In reply to Re^4: A working strategy to handle AUTOLOAD, can(), and (multiple) inheritance without touching UNIVERSAL?