> my first instinct would be to look into the "Open/Import" functionality of all those open source Spreadsheet tools like LibreOffice.

I already mentioned the Excel's import wizard, but it's mainly meant for CSV and not free-form tables.

> If an AI goes wrong, all you can do is tweak the training data, retrain the model and pray to a $DEITY of your choice that

As I said, that's also not the way I would go.

The AI should

• a TK window with a preview with the interpretation(s) and options to improve
• create a "wizarded" Perl code

This code should be validating too, hence be more fault tolerant the most hand crafted code.

(like detecting unusual data, like text in a field which always used to be numerical)

Ideally the Perl code could also include data to restart the Tk-Wizard to refince in case of errors.

I think that would easily address all your concerns.

PS: Of course this could also be a realized as a web service and skip the Tk part.