That would be really nice, yes. Unfortunately for would-be authors of such tools, Perl isn't well-suited to such interrogation. This is partially because the syntactic flexibility allows people to write really bad code: the kind which only perl can really parse.

So, you have to start with the assumption that the code follows some kind of guidelines or best practices. That's a big assumption -- after all, if the programmer were disciplined enough to follow good coding practices, she would have already documented well, and this issue wouldn't exist.

Also, consider that things like required arguments are not language-native. Subroutines are not declared in a way that says 'arguments foo, bar, and baz are required, and aleph and beth are optional'. Sometimes there are prototypes, but they are generally avoided (and for good reason). Some scripts will not even have subroutines, since it isn't required by Perl.

All of these things are positive from a developer standpoint: they make Perl a very powerful and flexible tool. From the standpoint of trying to automatically determine how given code functions, it's a thorn.