n>]
 (<span class="mdzsyn-coresym">def</span> <span class="mdzsyn-symbol">oldx</span> <span class="mdzsyn-symbol">*my-binding*</span>)
 (<span class="mdzsyn-coresym">set</span> <span class="mdzsyn-symbol">*my-binding*</span> <span class="mdzsyn-symbol">x</span>)
 (<span class="mdzsyn-symbol">may-error</span>)
 (<span class="mdzsyn-coresym">set</span> <span class="mdzsyn-symbol">*my-binding*</span> <span class="mdzsyn-symbol">oldx</span>))</code></pre><p>This example is a bit verbose, but most importantly it