Lisp if not nil
<p>I am so sorry for having to ask this question but I'm trying to do a simple <code>if</code> statement that checks if a variable is <code>nil</code> or not.</p>

<pre><code>(defun test (input)
  (let ((testvar (first input)))
   (if (not nil testvar)
    (do this)
    (do that))))
</code></pre>

<p>Could anyone explain the proper syntax to me?</p>