How about you provide a data sample about the size of that you have given already, but sufficiently complete to show the problems you are seeing, and sample code that is representative of the code you are using, but which we can run. The following sample may help as a starting point:

#!/bin/perl
use strict;
use warnings;
use XML::Twig;
use Tie::IxHash;

my %Items;
tie %Items, "Tie::IxHash";
my $xml = <<XML;
<Catalog>
  <item>
    <quantities>
      <prices/>
    </quantities>
    <sellingpoints/>
  </item>
  <item>
    <quantities>
      <prices/>
    </quantities>
    <sellingpoints/>
  </item>
</Catalog>
XML

my $twig = XML::Twig->new( twig_handlers => { _all_ => \&handler, } );
$twig->parse($xml);    # build it
$twig->purge;          # clear end of document from memory

print "\n";
print "$_ => $Items{$_}\n" for keys %Items;


sub handler {
    my $Item_master_Ancestory = $_->ancestors;
    my $element_match         = $_->tag;
    my $text                  = $_->trimmed_text;
    my $coupled               = join
        ' - ', "  " x $Item_master_Ancestory,
        $element_match, keys %{ $_->atts }, values %{ $_->atts }, $tex
+t;

    ++$Items{$coupled};
    print "$coupled: $Items{$coupled}\n";
}
[download]

Prints:

       - prices - : 1
     - quantities - : 1
     - sellingpoints - : 1
   - item - : 1
       - prices - : 2
     - quantities - : 2
     - sellingpoints - : 2
   - item - : 2
 - Catalog - : 1

       - prices -  => 2
     - quantities -  => 2
     - sellingpoints -  => 2
   - item -  => 2
 - Catalog -  => 1
[download]