Jack doesn't quite remember when or why he starts making a list, but he starts doing it all the same.
It's sort of a silly list, actually, now that he thinks about it. He could spend his time and money on many better things, but he likes doing this – originally thinks he's doing it for Lacie, even, though she never notices or compliments him or tells him that she likes things or dislikes things like Oswald (no, Glen, he had to keep reminding himself that he was Glen now) does.
He already has an extensive collection of perfume, anyway. He doesn't need more.
All the same, he can't help but notice what Glen likes on him, and is inclined to hoard bottles of it. Nothing too heavy – nothing woody, nothing musky. Glen likes him in florals – airy, ethereal florals, frosty lilac and violet leaf, a touch of osmanthus and maybe something mossy. The perfumes Glen likes on him aren't overly feminine, but they're soft, far more delicate than what most men would chose to wear, but Jack doesn't mind.
He takes too much pride in making Glen notice him, after all; in the way Glen's head lifts up when Jack drifts behind him at the piano, in the way he can catch just the faintest scent of oils that were brushed along his braid earlier that morning.
He has a list of three or four that Glen really does prefer at this point, and alternates them, depending on the day. There's something about making Glen guess, about watching his expressions when he can smell Jack coming – can smell something that is almost fae-like, especially when Glen is out by the lake, staring blankly into the water, and Jack is already amongst wilderness in the forest behind him, scented like everything but wood, fresh and like wet grass and pulled iris roots and perhaps like some of the sweetness of decadent white chocolate Glen himself likes to nibble upon.
Jack's greatest triumph, after all, is when Glen reaches for him first – presses his face into the side of Jack's neck and inhales, inhales everything that is Jack, perfume and skin and softness and the hot beating of his pulse as he whimpers and burrows closer. Because he can't help it – he's drawn to this man, the head of the Baskervilles that killed the person he loved, that killed his own sister.
Jack has always known he was depraved, but god, this takes the cake.