#lang racket

(require net/url)

(provide (contract-out [live-web-value (-> string? string? string? 
                                           number?)])) 

(define (live-web-value url key-line regexp-pattern)
  (let* ((in (get-pure-port (string->url url)))
         (the-line (do ((the-line (read-line in) (read-line in)))
                     ((regexp-match key-line the-line) the-line))))
    (string->number (first (regexp-match regexp-pattern the-line)))))