my $filter = XML::Rules->new(style => 'filter', rules => {
  'XREF' => {
     qr{/LinkValue$} => sub { 
       return $references{$_[1]->{_content}} ?? "Unknown reference $_[1]->{_content}";
     }
# or
#    qr{/Property/LinkValue$} => sub { 
#      return $references{$_[1]->{_content}} ?? "Unknown reference $_[1]->{_content}";
#    }
# for only <Property><LinkValue><XREF>
   
  }
});