The CPAN documentation seems plentiful but incomplete. For example, if there are parameters for Tk::MainLoop or any special methods for Tk::MainWindow it can't be discerned from the documentation.
I have the Perl/Tk Pocket Reference by Stephan Lidie. I counted 27 methods that can be called on a mainwindow in that chapter. Appendix A of Learning Perl/Tk has a table of common widget methods. But that book is out of print. I don't know about the Pocket Reference. But is very handy and has a lot more than the Appendix A table. This isn't a tutorial, it is a "cut to the chase", here is a widget and here are the methods. There aren't any examples.
$10 on Amazon. I recommend this.