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

my $doc = XML::LibXML->load_xml(string => <<END_XML);
<TT>
 <A>xyz<B>test1</B></A>
 <!-- my comment -->
</TT>
END_XML

# Print everything
my ($node_a) = $doc->findnodes("/TT/A");
$node_a->appendTextNode('-123-'); 
$node_a->appendTextNode('-456-'); 
print $doc->toString, "\n";
my $count=1;
foreach($doc->findnodes("/TT/A/text()")){
    print $count++,": ", $_->data, "\n";
}
__END__
<?xml version="1.0"?>
<TT>
 <A>xyz<B>test1</B>-123--456-</A>
 <!-- my comment -->
</TT>

1: xyz
2: -123--456-