I have seen some Tk-based apps (not only in perl, but python as well) get bogged down because of creating way too many widgets inside other widgets. (This apparently runs contrary to Marshall's experience, but it's obviously a possible, even likely outcome.)

So the idea in the first reply is the direction I would take, IF it's really the case that a user needs to see a bunch of adjacent lines in order to do what needs to be done manually.

If each "row" in your text file involves a set of user decisions that are independent of the decisions made on any other row, that's an even better reason for having a separation between search/review/select activities and edit/update activities. A total of maybe 8 widgets for the former, and 20 for the latter, should give you a simple, clean, fast and easy-to-use interface.