#!/usr/bin/perl
use warnings;
use strict;

use XML::LibXML;

my $xml = XML::LibXML->load_xml( location => '1.xml');
my $xpc = XML::LibXML::XPathContext->new($xml);
$xpc->registerNs('contact', 'urn:ietf:params:xml:ns:contact-1.0');
for my $name (qw(rem add)) {
    for my $node ($xpc->findnodes("//contact:$name".'[not(*|text()|@*|processing-instruction()|comment())]', $xml->documentElement)) {
        $node = $node->parentNode->removeChild($node);
    }
}
print $xml->serialize;