;; Print every item in a list.
 (loop for item in '(1 2 3) do (print item))
 |>  1
 |>  2
 |>  3
⇒  NIL

;; Print every other item in a list.
 (loop for item in '(1 2 3 4 5) by #'cddr
       do (print item))
 |>  1
 |>  3
 |>  5
⇒  NIL

;; Destructure a list, and sum the x values using fixnum arithmetic.
 (loop for (item . x) of-type (t . fixnum) in '((A . 1) (B . 2) (C . 3))
       unless (eq item 'B) sum x)
⇒  4