use strict;
use warnings;

use XML::TreeBuilder;

my $xml = <<'END';
  <inventors type="array">
    <inventor>
      <city>Aston Clinton</city>
      <name>Andy Barth</name>
      <number type="integer">1</number>
      <country>GB</country>
      <upper-name>ANDY BARTH</upper-name>
    </inventor>
    <inventor>
      <city>Aylesbury</city>
      <name>Daniele Dall'Acqua</name>
      <number type="integer">2</number>
      <country>GB</country>
      <upper-name>DANIELE DALL'ACQUA</upper-name>
    </inventor>
    <inventor>
      <city>Calne</city>
      <name>Nigel Drew</name>
      <number type="integer">3</number>
      <country>GB</country>
      <upper-name>NIGEL DREW</upper-name>
    </inventor>
  </inventors>
END

my $tree=XML::TreeBuilder->new();
 $tree->parse($xml);

my @inventornums=$tree->find_by_tag_name('number');

foreach my $inventornum(@inventornums){
	if ($inventornum->as_text()==2){
		my $parent=$inventornum->parent();
  		print $parent->as_XML;
  	}

}