.EQ thing1 thing2

	outputs TRUE if its two inputs are the same datum, so that applying a
	mutator to one will change the other as well.  Outputs FALSE otherwise,
	even if the inputs are equal in value.
	WARNING: Primitives whose names start with a period are DANGEROUS.
	Their use by non-experts is not recommended.  The use of mutators
	can lead to circular data structures, infinite loops, or Logo crashes.