user=> (def a (atom 10))                                
#'user/a

user=> (while (pos? @a) (do (println @a) (swap! a dec)))
10
9
8
7
6
5
4
3
2
1
nil

user=> (def a (atom 10))                                
#'user/a

user=> (while (pos? @a) (do (println @a) (swap! a dec)))
10
9
8
7
6
5
4
3
2
1
nil