The UNIVERSAL class provides a few default methods so that all objects can use
them. Object orientation allows programmers to override these methods in
subclasses to provide more specific and appropriate behavior.
Some authors call methods in the UNIVERSAL class on potential invocants as
functions, bypassing any possible overriding. This is wrong and you should not
do it. Unfortunately, not everyone heeds this warning and their bad code can
break your good code.
This module replaces UNIVERSAL::can() with a method that checks to see if
the first argument is a valid invocant has its own can() method. If so, it
gives a warning and calls the overridden method, working around buggy code.
Otherwise, everything works as you might expect.
Some people argue that you must call UNIVERSAL::can() as a function because
you dont know if your proposed invocant is a valid invocant. Thats silly.
Use blessed() from Scalar::Util if you want to check that the potential
invocant is an object or call the method anyway in an eval block and check
for failure (though check the exception returned, as a poorly-written
can() method could break Liskov and throw an exception other than You cant
call a method on this type of invocant).
Just dont break working code.
Inspired by UNIVERSAL::isa by Yuval Kogman, Autrijus Tang, and myself.
Adam Kennedy has tirelessly made me tired by reporting potential bugs and
suggesting ideas that found actual bugs.
Mark Clements helped to track down an invalid invocant bug.
Curtis Ovid Poe finally provided the inspiration I needed to clean up the
Peter du Marchie van Voorthuysen identified and fixed a problem with calling
Daniel LeWarne found and fixed a deep recursion error.
Norbert Buchmueller fixed an overloading bug in blessed invocants.
The Perl QA list had a huge... discussion... which inspired my realization that
this module needed to do what it does now.