Most of the gui-creators are designed for Win32, and cost money. There is the Prima project, at Prima. It is kind of big and bloated and you end up not learning Tk very well. You will find that once you learn how to setup a basic main window, writing Tk is easier if done from scratch. At http://www.perltk.org (the link is down as I write), you can find "Visual PerlTk" or vptk. It could be useful in just widget placement, try it and see.

Everyone is looking for a Tk development tool like the old Visual Basic, where you right click on the widget, and just select the widget options and callbacks. Ala Qumsieh on comp.lang.perl.tk is trying to develop "ZooZ" which is like this, but it is still in early development. And has drawbacks, like only uses grid manager.

I really liked the way Glade worked for Gtk. It would be nice if there was something like that for Tk.

In the mean time, there are some nice Tk tools, written by Slaven Rezic which aid in widget setup and design. Check out: Widget Dump and Tk::ObjEditor and Tk::ObjScanner from cpan.