In addition to what has already been said, you will probably want to delete what's already in the boxes, before you add your word.(or maybe not.... :-) )

#for an entry widget
$entry->delete(0,'end');
$entry->insert(0,$word);
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#for a textbox
$text->delete("1.0","end");
$text->insert('end',$word);
$text->see('end');
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