Check the addition of the last expression.

>>>>templates/test.tpl
The text
<foo>The tag</foo>
{$foo}

>>>>data.php
$this->tpl->prologRequired = false;
$this->tpl->singleRootNode = false;
$view->foo = 'FOO';

>>>>expected.txt
OUTPUT

>>>>result.txt
The text
<foo>The tag</foo>
FOO