title: Difference between use and run in Rack
body: <p>What's the difference between the <code>use</code> and <code>run</code> methods in rackup files? It seems <code>run</code> is always at the end of <code>config.ru</code>, but it seems as if you should just be able to use <code>use</code>. Enlightening resources would also be very much appreciated.</p>