lrest returns a list of all but the first element of a non-empty list:
lrest([3, 5, 7, 11, 13]) ==> [5, 7, 11, 13]
lrest([[3, 5, 7], 11, 13]) ==> [11, 13]
lrest([ ]) doesnŐt make sense; it returns an error value
lBe sure that the argument to rest is not [].