If you want to use a regexp in the condition, the only way to do it is to have the condition be a regexp, that will be applied to the tag itself (ie you can't apply it to the whole path):

 #!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

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

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

It would be nice to at least be able to apply the regexp to the path, so you could write qr{/result/target/tag[1-3]}. I'll look into it. Further than that, I don't think XML::Twig can do better, at least as it is currently implemented. Allowing the "xpath-like" interpreter to deal with XPath regexp syntax (start-with and the likes) would be a bit difficult, and Perl's regexp syntax and the XPath syntax collide ( [...] is a character class for Perl and a predicate for XPath), so not much hope there.