"you may Pass this to the player on your left" (i.e. gain to their hand). Then if you end the game this turn, they get +1VP. Otherwise, they at least have the option/choice to Pass it to the next person instead of keeping it for -2VP.
Passing is not gaining; you cannot Watchtower the card you get passed via Masquerade, for example. With your suggested wording, passing Monkey's Paw would result in it always being worth -2
for your opponent, because they did not gain it at all and therefore did not "gain it after their last turn of the game."
I do agree with you that it's really hard/impossible to track the
value of the Monkey's Paws, though. As currently worded, at least, each individual copy can be worth varying amounts of
, which is impossible to track in an irl game.