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

my $hash = {
	'root' => {
		'item1' => {
			'item1a' => 'n1', 'item1b'=>'jh'
		}
	}
};

my $dom = XML::LibXML::Document->createDocument();

# recursively convert hashes to elements
my $frag = $dom->createDocumentFragment();
my $hash2el; $hash2el = sub {
	my ($n,$h) = @_;
	for my $key (sort keys %$h) {
		my $el = $dom->createElement($key);
		if (ref $h->{$key} eq 'HASH')
			{ $hash2el->($el, $h->{$key}) }
		else { $el->appendText( ''.$h->{$key} ) }
		$n->appendChild($el);
	}
};
$hash2el->($frag, $hash);

# either a single root node, or multiple nodes in a new root
my @roots = $frag->nonBlankChildNodes();
if (@roots==1) {
	$dom->setDocumentElement( $roots[0] );
}
elsif (@roots>1) {
	my $root = $dom->createElement('root');
	$root->appendChild($frag);
	$dom->setDocumentElement( $root );
}

print $dom->toString(1);

__END__

<?xml version="1.0"?>
<root>
  <item1>
    <item1a>n1</item1a>
    <item1b>jh</item1b>
  </item1>
</root>