<include src="included_sample.html">
<if expr="True">
should be kept
</if>
in the middle...
<if expr="False">
should be removed
</if>

<if expr="False">
should be removed
  <if expr="True">
    should be removed because outer expr is False
  </if>
should be removed
</if>

<if expr="True">
  <if expr="True">
    <if expr="True">
      nested true should be kept
    </if>
    <if expr="False">
      should be removed
    </if>
  </if>
  <if expr="True">
    silbing true should be kept
  </if>
</if>
at the end...
