Question Author
Davebro got their first, just ahead of scorpiojo. Well done to both of you.
B is given, so locating 'perturb' isn't difficult.
As for environtmentally-friendly, I've come across a complete Alphapuzzle that was identical to one from ~18 months ago, so must have been copied. I would imagine that this happens much more than most people imagine. The clue-solving databases already store plenty of clues and their solutions. As for Alphapuzzles, I personally have records of many hundreds of them (including 'Enigma' puzzles) going back at least 8 years. If these could be searched, I'm sure there would be a lot of duplication. (Bring back the old Google Desktop!)