For the code from tobyink

use strict;
use warnings;
use XML::LibXML 2;

my $doc = 'XML::LibXML'->load_xml(IO => \*DATA);

foreach my $node ( $doc->findnodes('//ReferenceID') )
{
    $node->firstChild->setData("Reference ID type is $node->{reference
+IDType}")
        if $node->{referenceIDType} eq 'FXDD';
}

print $doc->toString;
[download]

when i use $node ->setData("xyz"); i again get the same error. Please excuse my ignorance, i am very new to perl scripting.