on

Creates one or more execute commands on a relation to the given entity

This can be nested with if_, as_, align, anchored, at, in_, facing, on, positioned, positionedAs, positionedOver, rotated, rotatedAs and summon to create more complex conditions

Example:

on_(RelationArg.ATTACKER) {
  cmd("say Hello World!")
  at_("notch") {
    cmd("say Hi!")
  }
  if_(con("C")) {
    cmd("say C was true too!")
  }
}