span class="special">&amp;&amp;</span> var<span class="special">)</span><span class="special">;</span>

      <span class="comment">// Return lvalue reference to T, throws unspecified exception if type does not match. </span>
      <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> Us<span class="special">&gt;</span> <span class="identifier">T</span> <sp