#!/usr/bin/perl -w
use strict; 

use XML::Twig;
use YAML;

my %hash;
XML::Twig->new( twig_handlers =>
                  { elt => sub { $hash{$_->field('key')}= $_->field('value');
                                 $_->insert_new_elt( first_child => ts => scalar localtime);
                                 $_[0]->flush; # flushes the doc to use less memory (might be overkill ;--)
                               }
                  },
                pretty_print => 'record_c',
              )
          ->parse( \*DATA)
          ->flush; # to flush the closing tag for doc

print "\n\nHASH:\n", Dump \%hash; 

__DATA__
<doc>
  <elt><key>key1</key><value>value1</value></elt>
  <elt><key>key2</key><value>value2</value></elt>
  <elt><key>key3</key><value>value3</value></elt>
  <elt><key>key4</key><value>value4</value></elt>
</doc>