use XML::LibXML;

my $dom = 'XML::LibXML'->load_xml(IO => *STDIN);

for my $child (
    @{ $dom->find('/tmx/body/tu/tuv[@xml:lang=\'en\']/seg | /tmx/body/tu/tuv[@xml:lang=\'fr\']/seg | tmx/body/tu/prop | /tmx/body/tu/@creationdate') }

) {
    ( my $contents = join '', $child->childNodes ) =~ s,\n, <lb/> ,g;
    print $contents, $child->nodeName eq 'source' ? "\t" : "\n";
}