If I use XML::Twig, this code works if I have 1 'article' element, or 2 or 3 (I didn't try more than 3, but I believe it will work for 100). The output below shows the case with 2 articles (which is your XML example):

use strict;
use warnings;
use XML::Twig;

my $file_in = shift;
my $twig= new XML::Twig(
    twig_handlers => { reference => \&reference }
);
$twig->parsefile($file_in);
exit;

sub reference {
    my ($twig, $refer) = @_;
    print $refer->text(), "\n";
}  

__END__
distdoc:archive/ArchiveDoc::Article/MTPW000020090731e57v004mr
distdoc:archive/ArchiveDoc::Article/MTPW000020090731e57v004mr
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