Perl: unable to extract sibling value using Twig::XPath syntax - perl

Question

Recently I start to use XML::Twig::XPath but the module does not seem to recognize an xpath syntax.
In the following XML, I want the value of "Txt" node if the value of PlcAndNm node is "ext_1"
<?xml version="1.0" encoding="UTF-8"?>
<root>
<Document>
<RedOrdrV03>
<MsgId>
<Id>1</Id>
</MsgId>
<Xtnsn>
<PlcAndNm>ext_1</PlcAndNm>
<Txt>1234</Txt>
</Xtnsn>
<Xtnsn>
<PlcAndNm>ext_2</PlcAndNm>
<Txt>ABC</Txt>
</Xtnsn>
</RedOrdrV03>
</Document>
<Document>
<RedOrdrV03>
<MsgId>
<Id>2</Id>
</MsgId>
<Xtnsn>
<PlcAndNm>ext_1</PlcAndNm>
<Txt>9876</Txt>
</Xtnsn>
<Xtnsn>
<PlcAndNm>ext_2</PlcAndNm>
<Txt>DEF</Txt>
</Xtnsn>
</RedOrdrV03>
</Document>
</root>
I have tried whit expression //Xtnsn[PlcAndNm="ext_1"]/Txt but I received an error
This is the code:
use XML::Twig::XPath;
my $subelt_count = 1;
my #processed_elements;
my $xmlfile = 'c:/test_file.xml';
my $parser = XML::Twig->new(
twig_roots => { 'RedOrdrV03' => \&process_xml } ,
end_tag_handlers => { 'Document' },
);
$parser->parsefile($xmlfile);
sub process_xml {
my ( $twig, $elt ) = #_;
push( #processed_elements, $elt );
if ( #processed_elements >= $subelt_count ) {
my $MsgId = $twig->findvalue('RedOrdrV03/MsgId/Id');
my $Xtnsn_Txt1 = $twig->findvalue('//Xtnsn[PlcAndNm="ext_1"]/Txt');
print "MsgId: $MsgId - Xtnsn_Txt1: $Xtnsn_Txt1\n";
}
$_->delete for #processed_elements;
#processed_elements = ();
$twig->purge;
}
Is there a simple way of using xpath to obtain the value?
I know that a possibility is somenthing like:
my $Xtnsn_Txt1 = $twig->first_elt( sub { $_[0]->tag eq 'PlcAndNm' && $_[0]->text eq 'ext_1' })->next_sibling()->text();
but I prefer using the simplest XPath syntax,
Thanks in advance for your help!

Answer 1

You can use this:
my $Xtnsn_Txt1 = $twig->findvalue('//Xtnsn/PlcAndNm[string()="ext_1"]/../Txt');

Answer 2

Another approach could be :
//Txt[preceding-sibling::PlcAndNm[.="ext_1"]]
You can also modify a little bit your XPath expression to see if it works with :
//Xtnsn[./PlcAndNm[contains(.,"ext_1")]]/Txt
EDIT : This works fine with the original XML::XPath module :
use XML::XPath;
use XML::XPath::Node::Element;
my $xp = XML::XPath->new(filename => 'pathtoyour.xml');
my $nodeset = $xp->find('//Xtnsn[PlcAndNm="ext_1"]/Txt');
foreach my $node ($nodeset->get_nodelist) {
print XML::XPath::Node::Element::string_value($node),"\n\n";
}
Output : 1234 9876