Pass the object in only, not the subroutine name. Force all objects that are passed in to have a certain method name (which you can check with $obj->can('method_name') which you then call. If you need a single sub that can handle either an object OR a subreferance, just check the output of ref() and mix in some DWIM.

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated