 an option with expiry date argument, see <code>parse_expiry_date()</code>.
The timestamp is put into <code>timestamp_t_var</code>.</p>
</dd>
<dt class="hdlist1"><code>OPT_CALLBACK(short, long, &amp;var, arg_str, description, func_ptr)</code></dt>
<dd>
<p>Introduce an option with argument.
The argument will be fed into the function given by <code>func_ptr</code>
and the result will be put into <code>var</code>.
See <em>Option Callbacks</em> below for a more elaborate description.</p>
</dd>
<dt class="hdlist