Thanks for all the replies. The problem that served as context for the question is to devise an automatic way to define delegated methods.

sub frobozz {
  my $self = shift;
  return $self->{ _delegate }->frobozz( @_ );
}
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My basic idea was to run through all the "public methods" that the delegate can perform (by plucking them out of its and its ancestors' symbol tables) and define a delegated method (like the one illustrated above) for each of those methods among these that the containing class cannot perform.

The fly in the ointment, of course, is that fishing functions out of symbol tables, in general, cannot distinguish between public methods (which are part of the delegate's API) and private methods or functions that have been imported by the delegate class, and neither of which belong to its API.

The only thing I can think of is that, if all the ancestor classes are ones that I control, then I can define those classes so that their private methods are easy to distinguish (e.g. with leading underscores) and so that they don't import anything. They either use fully qualified function names, or do something like:

BEGIN {
  *_croak = \&Carp::croak;
}
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(Or I can go nuts and assign all these non-API methods to lexical scalars.)

And yes, the whole scheme described above would miss any AUTOLOADed or runtime-defined methods of the delegate object. Again, I don't know a way around this, other than avoiding using such methods in those classes I control.

I suspect that, as is my habit, I am complexifying things... As always, your comments are most welcome.