#!/usr/bin/perl
use strict;
use warnings;
use XML::Twig;
my $xml = 'value.xml';
my $twig = new XML::Twig(
  twig_handlers =>{ field => \&field }
);
$twig->parsefile($xml);

sub field {
  my ($t,$e) = @_;
  for ($e->children){
    if ($_->gi eq 'key'){
      print $_->att('name')." ";
    } elsif ($_->gi eq 'value'){      
      print $_->att('id')."\n";
    }
  }
}