/span> <span>&#45;&gt;</span> <span>unit Cmdliner.Term.t</span></code></dt><dd><p>Return a unit <code>Term</code> that evaluates the input term and set the reference to the resulting value.</p><p>Due to the nature of Cmdliner, this may be evaluated multiple times, so setting the reference to anything else is dangerous.</p></dd></dl><dl><dt class="spec value" id="val-add_option"><a href="#val-add_option" class="anchor"></a><code><span class="keyword">val</span> add_option : <span>unit Cmdliner.Term.t</span> 