my $parser = XML::LibXML->new();
my $doc = $parser->parse_file("main_file.XML");
my $doc1 = $parser->parse_file("second_file.XML");

my @nodes_from_main= $doc0->findnodes('//path/to/element/text()');
my @nodes_from_second = $doc1->findnodes('//path/to/element/text()');