ameters defined before the last variadic argument are
not optional, unless specified as so with the <code class="mendoza-code">&amp;opt</code> symbol.
</p>
<pre class="mendoza-codeblock"><code data-language="janet">(<span class="mdzsyn-coresym">defn</span> <span class="mdzsyn-symbol">my-adder</span>
 <span class="mdzsyn-string">"Adds numbers in a dubious way."</span>
 [<span class="mdzsyn-symbol">&amp;</span> <span class="mdzsyn-symbol">xs</span>]
 (<span class="mdzsyn-coresym">var</span> <span class="mdzsy