irst expression creates an anonymous function that adds twice
the first argument to the second, and then calls that function with arguments 10 and 20.
This will return (10 + 10 + 20) = 40.
</p>
<p>There is a common macro <code class="mendoza-code">defn</code> that can be used for creating functions and immediately binding
them to a name. <code class="mendoza-code">defn</code> works as expected at both the top level and inside another form. There is also
the corresponding macro <code class="mendoza-code">def