Free perks
Kowloon hides three ways to earn a free perk, on top of the Perkaholic of the main quest. The Steam guide Kowloon Complete Map Guide credits the forum posts of Arthys and Bobgang1 for several of them.

The red phones
From round 10, three red phones ring around the map: on the spawn roof, on a box next to the ammo crate; in the sewing room, on a desk across from Quick Revive; and on the main roof, on a barrel next to Stamin-Up, by the Krig 6 wall weapon. Answering all three, in any order, gives a free perk.

The pink gongs
Three pink gongs hang outside the map: behind the half-wall of the spawn roof; above Deadshot Daiquiri, best seen from Elemental Pop; and on the roof above Speed Cola, best seen from Tacti-Quilla. Shooting all three with the Sliquifier gives a free perk. Kunjora and a player on the Workshop forum say the Sliquifier does not need to be upgraded.
The three elephants
With the power on, drop from the ledge by Elemental Pop onto the half-roof of Widow’s Wine. Three ceramic elephants sit in a corner. Bring them three white tiles: one on the overhanging ledge behind the Speed Cola platform, one on the catwalk of the meteor room next to its broken part, and one on the upper roof, leaning against boxes to the right of Tacti-Quilla. The reward is a free perk.

