title: Parse comma-delimited string into vectors based on leading character
body: <p>Given a string:</p>
  
  <pre><code>vals &lt;- "-AB, CV, CL, -TS"
  </code></pre>
  
  <p>I would like to <em>efficiently</em> parse <code>vals</code> into two vectors (let's call them <code>negative</code> and <code>positive</code>), one containing the values prefixed by <code>-</code>, and the others not. One catch is that I would also like to remove the <code>-</code> indicator.</p>
  
  <p>Desired result:</p>
  
  <pre><code>&gt; negative
  [1] "AB" "TS"
  &gt; positive
  [1] "CV" "CL"
  </code></pre>
  
  <p>Bonus points for a compact answer.</p>