Free Hero Mesh

  If the input is a mark, then it is removed and the result is false.
  Otherwise, the value remains and true is added above it on the stack.

Trace  ( obj arg1 arg2 -- )
  If tracing is enabled, sends the three values and some other information
  on stdout. If tracing is disabled, does nothing. This is intended to be
  used for debugging class codes.

Trigger  ( obj message -- ) **
  Call a message for a pending trigger for the specified object immediately
  instead of waiting for its turn in the trigger phase. Only has an effect
  if the object does not have the Compatible flag. The message must be
  MOVED, DEPARTED, or ARRIVED; otherwise it is an error. If that trigger is
  pending, it will clear the trigger and send it like it does during the
  trigger phase, setting Arg1 as appropriate, but From is set to the object
  calling it instead of 0, and Arg2 and Arg3 will be inherited from the
  current values of those variables. The return value is ignored. Since the
  trigger is cleared before it is sent, it is safe for objects to call the
  triggers of objects in a loop.

TriggerAt  ( x ymessage -- ) **
  Works like Trigger on all objects at the specified location, from the
  bottom to the top.

tuck  ( x y -- y x y )

uniq  ( mark ... value -- mark ... value true | mark ... false )
  Check if the top value matches any others in the list above the mark. If
  it doesn't match any, then the value remains and it pushes true; if it
  does match, then the top value is removed and it pushes false instead.