ts</strong></span>: Returns a reference to the <a class="link" href="sub_match.html" title="sub_match"><code class="computeroutput"><span class="identifier">sub_match</span></code></a>
        object representing the character sequence that matched marked sub-expression
        <span class="emphasis"><em>n</em></span>. If <code class="computeroutput"><span class="identifier">n</span> <span class="special">==</span> <span class="number">0</span></code> then returns
        a reference to a <a class="link" hr