(defn get-price-from-url
  [url]
  (second (re-matches price-regex (fetch-url url))))

(defn get-price-from-urls
  [url-list]
  (map get-price-from-url url-list))

user> (map get-price-from-url [url1 url2])
("$15.32" "$15.32")
user> (get-price-from-urls [url1 url2])
nil