Natural weapon damage scales with size

[direinsomniac]

I've been away from coding HL for a few years, and now some of the normal syntax I would use don't seem to be working like they used to.

I am trying to have a subtype get a Slam attack that scales up or down based on the size of the base creature.

I've tried

perform hero.child[wSlam].field[wDamage].value += 1

and HL doesn't like the perform tag anymore.

Syntax error in 'bootstrap #1 condition' tag expression for Thing 'stMyFile' 
-> Invalid tag template specified: 'perform'

I have the wSlam ability bootstrapped with Tags:
Helper = NatPrimary
wMain = 1d6


I'd appreciate a bit of clarification on how the scripting/syntax may have changed.