my $dom = 'XML::LibXML'->load_xml(location => 'test.osm');
for my $node ($dom->findnodes('/osm/node')) {
    my $tag = $node->findnodes('tag[@k="name"]')->[0];
    my $key = "$node->{lat}.$node->{lon}";
    if (exists $HoH{$key}){
        $tag->{v} = $HoH{$key}->{name};
        $node->{id} = $HoH{$key}->{id};
    }
    else {
        foreach my $key (keys %HoH) {
           #print $key,"\n";
           my ($lat_key,$lon_key) = (split /[.]/, $key)[0,2];
           my $new_node = 'XML::LibXML::Element'->new("node");
           my $id = 'XML::LibXML::Attr'->new("id",$HoH{$key}->{id});
           my $lat = 'XML::LibXML::Attr'->new("lat",$lat_key);
           my $lon = 'XML::LibXML::Attr'->new("lon",$lon_key);
           $new_node->setAttribute($id);
           $new_node->setAttribute($lat);
           $new_node->setAttribute($lon);
           my $new_node_child = 'XML::LibXML::Element'->new("tag");
           my $k = 'XML::LibXML::Attr'->new("k",'name');
           my $v = 'XML::LibXML::Attr'->new("v",$HoH{$key}->{name});
           $new_node_child->setAttribute($k);
           $new_node_child->setAttribute($v);
           $new_node->addChild($new_node_child);
        }
    }
}
$dom->toFile('new_test.osm');