title: Haskell: URL encoding for post data
body: <p>I've been looking at <a href="http://hackage.haskell.org/packages/archive/HTTP/4000.2.3/doc/html/Network-HTTP.html" rel="noreferrer"><code>Network.HTTP</code></a>, but can't find a way to create properly URL encoded key/value pairs.</p>
  
  <p>How can I generate the post data required from <code>[(key, value)]</code> pair list for example? I imagine something like this already exists (perhaps hidden in the <code>Network.HTTP</code> package) but I can't find it, and I'd rather not re-invent the wheel.</p>