e>  <span class="nv">undo: </span><span class="o">-&gt;</span>
    <span class="k">return</span> <span class="kc">false</span> <span class="nx">unless</span> <span class="nx">@canUndo</span><span class="p">()</span>
    <span class="nx">@redos</span><span class="p">.</span><span class="nx">push</span> <span class="nx">@state</span>
    <span class="vi">@state = </span><span class="nx">@undos</span><span class="p">.</span><span class="nx">pop</span><span class="p">()</span>
    <span class="nx">@trigger</spa