Having a tool won't really help you understand how the geometry managers do their work
Find in below links ZooZ/Guido/TikiArtist/SpecTcl which are available, not sure if its what you want
perl Tk help, RFC: Learning Perl/Tk, Perl/Tk: For Beginners, Re^3: Tkx Search for dialog box for text input , Re: TclTk interface with Perl code, is it possible? , Re^2: GUI toolkit+designer for the perl newbie , Re: Easier GUI, Re: Should I use Perl/TK?, Re^2: need a popup gui stdin, Tk Tree Tutorial ( http://www.rtapo.com/tutorials/tk_tree.html ), some Tkx tutorial links, Tutorial http://theoryx5.uwinnipeg.ca/perltk/ and http://www.perl.com/pub/1999/10/perltk/, http://perltk.org/, http://web.archive.org/web/20100310202528/http://theoryx5.uwinnipeg.ca/perltk/, How to RTFM Tk Tutorials