It states that the lines

  curl("http://duckduckgo.com/", "-o page.html", "--silent")
  curl("http://duckduckgo.com/", "-o", "page.html", "--silent")

are equivalent. This worries me, I would much rather always have it be one argument corresponding to exactly one shell argument. Here it looks like in some (maybe all?) cases arguments are split on spaces, which means always having to be extremely cautious about escaping, something a good abstraction shouldn't force you to deal with.