mat of the error message generated when an command-line option is provided that is not defined in the processor.
		If this field evaluates to false then any command-line option provided that match the option pattern (see field <code>_optpat</code>) and is not defined is processed as a string option.
		The default value for this field is <code>"unknown option '%s'"</code>.
	</dd>
</dl>

<h3>Meta-Fields</h3>

<dl>
	
	<dt><code><b>__call</b></code></dt>
	<dd>
		Receives as arguments a sequence of string values