ntext.  &lt;expression<sub>2</sub>&gt; itself is not in a tail context.</p>
<p>
</p>
</ul>
<p></p>
<p>
Certain built-in procedures are also required to perform tail calls.
The first argument passed to <tt>apply</tt> and to
<tt>call-with-current-continuation</tt>, and the second argument passed to
<tt>call-with-values</tt>, must be called via a tail call.
Similarly, <tt>eval</tt> must evaluate its argument as if it
were in tail position within the <tt>eval</tt> procedure.</p>
<p>
In the following example the