I would suggest:

• The widget program, which should be in the same directory as your perl binary (probably /usr/bin/widget on Unix, or c:\Perl\bin\widget.bat on Windows)
• Either of the two Perl/Tk books, learning or mastering
• http://www.perltk.org/
• The fine documentation, including the overview
• And, of course, the monastery, if you have any specific questions.

Myself, I found the widget examples to be the most useful.

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'