Change the value vs. change where the variable points to.

alter-var-root-ex.txt

user=> (def x (atom 1))
#'user/x
user=> (def y x)
#'user/y
user=> @x
1
user=> @y
1
user=> (swap! x inc)
2
user=> @y
2
user=> @x
2
user=> (alter-var-root #'x (fn [_] "Hello"))
"Hello"
user=> @y
2
user=> x
"Hello"