#!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

XML::Twig->new( twig_handlers => { qr/^tag[1-3]/ => sub { print $_->tag, ": ", $_->text, "\n"; } })
         ->parse( \*DATA);

__DATA__
<result>
  <target type="aim">
    <tag1>123</tag1>
    <tag2>456</tag2>
    <nottag>789</nottag>
  </target>
</result>