This may be faintly heretical but a good book on Tcl/Tk might help with the Tk side of things. I learned Tcl/Tk first (all the time wishing the language wasn't so weird) and was overjoyed to discover Perl/Tk.

Usual advice (as given to me by lots of nice people recently) applies: find a project and apply Perl/Tk to it. Mine was a program to display current weather conditions given local meteorogical information, it's still being used :-) although I'm not especially proud of some bits of the code.

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Kevin O'Rourke