command /shulkerdamage <player> <text>:
   usage: &4/shulkerdamage <player> <false|true>
   permission: shulkerdamage.sk
   trigger:
      if arg-2 is "true":
         set {shulker-player%arg-1%} to "true"
      else if arg-2 is "false":
         set {shulker-player%arg-1%} to "false"

on damage of player:
   {shulker-player%victim%} is "false"
   attacker is shulker
   cancel event