The `when` form is for side effects; the `if` form should be preferred for functional code.

Also, I don't think we need an implicit "/" prefix. That can be specified on the `:browser-uri` key itself.

I think something more like:

```clojure
(defn- open-browser-to [server options]
  (str "http://" (server-host server) ":" (server-port server) (:browser-uri options)))
```