I cannot really say that I could even write a simple Hello World script in Perl/Tk, but you might want to use Tk::Canvas. As to how to detect clicked letters, have a look at perl/Tk. You could just use a plain text file as a data base; one line per word, tab delimited, second to last entry in a line being index words for the word.
This might, or might not help you; good luck anyways.
CombatSquirrel