Interesting, the Collins < on-line site >
I cited before, claims to be "The only online Scrabble checker to use the official tournament word list. The official word list includes over a quarter of a million permissible words, and is endorsed by Mattel and the World English-Language ScrabbleTM Players’ Association"Official"
As well as having 'pert' as an adjective, it also has it as a noun (a pert person) so accepts 'perts'
However it rejects 'warth'
In accordance with the board game, it also rejects proper nouns which must be spelt with a capital, but apparently there is a venus marine bivalve mollusc, so that's OK.
In my experience finding linked words that are awkward to transform one to the other is quite tricky. Either there seem to be fairly simple multiple options or none at all! That's why I was pleased to hit on the drunk/sober combination. Consequently all challenging contributions are gratefully received, but best to limit it to one at a time I suppose.
It also would be nice to grade equal length solutions so that the one that used the least obscure words is considered to be the winner, but I don't see how that can be decided impartially.
If this thread continues to be a welcome diversion from the complexities of Sudoku logic, I'll edit the OP so that only words that pass the Collins word checker will be accepted. That way everyone will know where they stand.