 returns <code class="mendoza-code">nil</code>.
</p>
<pre class="mendoza-codeblock"><code data-language="janet">(<span class="mdzsyn-coresym">var</span> <span class="mdzsyn-symbol">key</span> (<span class="mdzsyn-coresym">next</span> <span class="mdzsyn-symbol">alphabook</span> <span class="mdzsyn-constant">nil</span>))
(<span class="mdzsyn-coresym">while</span> (<span class="mdzsyn-coresym">not=</span> <span class="mdzsyn-constant">nil</span> <span class="mdzsyn-symbol">key</span>)
  (<span class="mdzsyn-c