#!/usr/bin/perl -w
use strict;
use XML::LibXML;

# NAmespaces
my $ONE_ns = 'ONE:';
my $ONE_pfx = 'O';
my $TWO_ns = 'two:IS:a_namEsp';
my $TWO_pfx = 'T';

# The XML Document
my $DOC = XML::LibXML->createDocument( "1.0", "UTF-8" );

# Set the root
my $root = $DOC->createElement('ABC');
$DOC->setDocumentElement($root);

# Establish namespaces
$root->setNamespace($ONE_ns, $ONE_pfx, 1);
$root->setNamespace($TWO_ns, $TWO_pfx, 0);

# Build the document tree
my $this = &appendOZ($root);
$this = &appendTZ($this);

print $DOC->toString(1);

sub appendOZ {
    my $root = shift or die;
    $root->addNewChild($ONE_ns, 'ZZZ');
    return $root;
}

sub appendTZ {
    my $root = shift or die;
    my $this = $root->addNewChild($TWO_ns, 'ZZZ');
    &appendOQ($this);
    return $root;
}

sub appendOQ {
    my $root = shift or die;
    my $this = $root->addNewChild($ONE_ns, 'QWERTY');
    &appendTU($this);
    return $root;
}

sub appendTU {
    my $root = shift or die;
    $root->addNewChild($TWO_ns, 'UIOP');
    return $root;
}