To be honest, I don't think teaching newbie Tk is a good idea.
If platform is Linux, using Gtk2 coz of Glade.
if platform is Win$, using Wx coz Wxdesigner
or you can even use C# form with a built-in perl interpreter.
My experience is:
Never use a GUI module without a usable RAD tool, unless you are sure you would use it often in next 10 years.
Coz you have to invest many in this module to be familiar with its grammar, tricks or other details.
you can do such effort on html/css, coz it seems not to be dead in next 5 years.
I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction