Check out B::Lint. Here's an excerpt from the manual:

undefined-subs
        This option warns whenever an undefined subroutine is invoked.
        This option will only catch explicitly invoked subroutines suc
+h
        as "foo()" and not indirect invocations such as "&$subref()" o
+r
        "$obj->meth()". Note that some programs or modules delay
        definition of subs until runtime by means of the AUTOLOAD
        mechanism.
[download]

ihb

Read argumentation in its context!