<span class="hljs-keyword">maybe</span>
    {ok, A} ?= a(),
    <span class="hljs-literal">true</span> = A &gt;= <span class="hljs-number">0</span>,
    {ok, B} ?= b(),
    A + B
<span class="hljs-keyword">else</span>
    error -&gt; error;
    wrong -&gt; error
<span class="hljs-keyword">end</span>
