Sets value of object VAL to the value of object ID. If such an object is found on the local stack frame, its value will be changed to VAL. If such an object doesn’t exist, then it will be created in local memory of current function. If ID is list, then it will be evaluated, and assignment will be made to that evaluation result.
Example:
(LET myvar ‘(3 4 5)) ; assign list to ‘myvar’ atom
(LET (CAR myvar) 5) ; replace the first element of ‘myvar’ list to 5.