PROJ USERDATA
PROJ_USERDATA is a defineprojectile property used to store additional data about a projectile which can be checked and acted upon by scripts during gameplay.
Syntax is:
defineprojectile <tile number> PROJ_USERDATA <number>
Where <number> is a 32-bit integer.
Suggested use: When an actor is hit by the projectile (as detected with ifwasweapon or similar), the userdata on that type of projectile can then be checked and linked to additional effects. Treating the userdata as a bitfield can help maximize its usefulness.