<Data>
  <References>
    <Devices>
      <Device name="dev1" description="123" address="abc"/>
      <Device name="dev2" description="123" address="abc"/>
      <Device name="dev3" description="123" address="abc"/>
      <Device name="item1" description="123" address="abc"/>
      <Device name="item2" description="123" address="abc"/>
      <Device name="item3" description="123" address="abc"/>
      <Device name="item4" description="123" address="abc"/>
      <Device name="item5" description="123" address="abc"/>
      ...
    </Devices>
  </References>
  <DeviceTree>
    <DeviceItem name="dev1">
      <PortItem name="1" description="info1-1">
        <DeviceItem name="item1"/>
      </PortItem>
      <PortItem name="2" description="info1-2">
        <DeviceItem name="item2"/>
        <DeviceItem name="item3"/>
      </PortItem>
      <PortItem name="3" description="info1-3">
      </PortItem>
    </DeviceItem>
    <DeviceItem name="dev2">
      <PortItem name="1" description="info2-1">
        <DeviceItem name="item4"/>
        <DeviceItem name="item5">
          <PortItem name="1" description="subinfo5-1">
            <DeviceItem name="item6"/>
            <DeviceItem name="item7"/>
            <DeviceItem name="item8"/>
          </PortItem>
          <PortItem name="2" description="subinfo5-2"/>
          <PortItem name="3" description="subinfo5-3"/>
        <DeviceItem>
      </PortItem>
      <PortItem name="2" description="info2-2">
      </PortItem>
      <PortItem name="3" description="info2-3">
        <DeviceItem name="dev3">
          <PortItem name="1" description="info3-1">
            <DeviceItem name="item9"/>
          </PortItem>
          <PortItem name="2" description="info3-2">
          </PortItem>
          <PortItem name="3" description="info3-3">
          </PortItem>
        </DeviceItem>
      </PortItem>
    </DeviceItem>
  </DeviceTree>
</Data>

my $node = $xml->find('//DeviceItem[@name=\'$key\']');

  my $d = $xml->find("//DeviceItem[\@name='$key']/ancestor::DeviceItem[starts-with(\@name,'CORE-')][1]/\@name");
  my $p = $xml->find("//DeviceItem[\@name='$key']/ancestor::PortItem[ancestor::DeviceItem[starts-with(\@name,'CORE-')][1]][1]/\@name");
  my $v = $xml->find("//DeviceItem[\@name='$key']/ancestor::PortItem[ancestor::DeviceItem[starts-with(\@name,'CORE-')][1]][1]/\@description");

  my $d = $xml->find("//DeviceItem[starts-with(\@name,'CORE-') and .//DeviceItem[\@name='$key'] and not(.//DeviceItem[starts-with(\@name,'CORE-')])]/\@name");
  my $p = $xml->find("//PortItem[parent::DeviceItem[starts-with(\@name,'CORE-')] and not(.//DeviceItem[starts-with(\@name,'CORE-')]) and .//DeviceItem[\@name='$key']]/\@name");
  my $v = $xml->find("//PortItem[parent::DeviceItem[starts-with(\@name,'CORE-')] and not(.//DeviceItem[starts-with(\@name,'CORE-')]) and .//DeviceItem[\@name='$key']]/\@description");