There are (rather too) many ways to do this in Perl because there are so many ways to do things in Perl. As someone commented, autoloaded methods will always be a bit tricky. However, rather than rolling your own approach I would suggest that you take a look at Class::Inspector on CPAN. That will let you do something like:
my $methods = Class::Inspector->methods( 'Foo::Class', 'full', 'public' );