Support Multiple Assignments & Swapping Variables
I think it'd be nice to also support multiple assignments, which therefore would open the door to swapping values in a single statement.
$ let a b c = [ 1 2 3 ]
$ echo $a
1
$ echo $b
2
$ echo $c
3
$ let a b = [ $b $a ]
$ echo $a
2
$ echo $b
1