Consider using XML::Twig for parsing XML

#!perl
use strict;
use warnings;
use XML::Twig;

my $twig = new XML::Twig(  twig_handlers =>{ 'Ss' => \&Ss } );
$twig->parsefile('ds_chY.xml');

sub Ss {
  my ($t,$e) = @_;
  my $obs = $e->first_child('Sequence')->first_child('Observed');
  print $e->att('ssId')."\t".$e->att('subSnpClass')."\t";
  print $obs->text."\n";
}
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UPDATE : added Observed

poj