use XML::LibXML ;
use strict;
use warnings;
{
    my $xml = <<'XML';
<?xml version="1.0" standalone="yes"?>
<sdnList>
  <sdnEntry>
    <lastName>Hello world!</lastName>
  </sdnEntry>
</sdnList>
XML
    my $parser = XML::LibXML->new;
    my $doc    = $parser->parse_string($xml);
    my $result = $doc->findvalue('//lastName');
    print $result;
}
{
    my $xml = <<'XML';
<?xml version="1.0" standalone="yes"?>
<sdnList xmlns="http://tempuri.org/sdnList.xsd">
  <sdnEntry>
    <lastName>Hello world!</lastName>
  </sdnEntry>
</sdnList>
XML
    my $parser = XML::LibXML->new;
    my $doc    = $parser->parse_string($xml);
    my $result = $doc->findvalue('//lastName');
    print $result ;
}