Undefined 値

MyLight = Targetspot pos:[10,20,100] target:(box())
-- check to see if MyLight has a target
if MyLight.target != undefined then
-- distance from light to target
dist=distance MyLight.pos MyLight.target.pos
else
-- distance from light to [0,0,0]
dist=length MyLight.pos
-- set CH_Hand1 to undefined so can test later to see if deleted
--deleteChangeHandler CH_Hand1; CH_Hand1=undefined