Polymorphic return values are really useful.  Often, we just want to
know if something worked or not.  Other times, we'd like to know what
the error text was.  Still others, we may want to know what the error
code was, and what the error properties were.  We don't want to handle
objects or data structures for every single return value, but we do want
to check error conditions in our code because that's what good
programmers do.

WWW: http://search.cpan.org/dist/Return-Value/