use XML::XPath;

my $xp = XML::XPath->new();
my $xml_pi = XML::XPath::Node::PI->new('xml', 'version="1.0"');
my $root = XML::XPath::Node::Element->new('root');
my $node = XML::XPath::Node::Element->new('node');
$root->appendChild($node);

# $root->printToFileFunction("filename.xml");