Calling tag on undefined value is probably the parent call. Adding a "defined" test there will probably do the trick. But I will suggest that the strength of the module is in using xpath so you rarely need to do a traverse in the first place. ≤/P>

The following more cautious code seemed to work for me and should purge memory regularly. I worry that calling purge on every element which might purge something you still need around.

use strict;
use warnings;

use XML::Twig;

$|++;

my $twig = XML::Twig->new(
    twig_handlers => {

        # as noted in the documentation for end_tag_handlers ...
        # "twig_handlers are called when an element is completely pars
+ed"
        # so should be safe to purge here
        'Book' => sub {
            my ($twig, $el) = @_;
#            print "purging ...\n";
            $twig->purge;
        },

        'Book//*' => sub {
            # see http://search.cpan.org/~mirod/XML-Twig-3.49/Twig.pm#
+cond
            # for #ELT which is an element
            print $_->tag, ': ', $_->text, $/
                unless ($_->has_children('#ELT'));
        }

    }
);
$twig->parsefile('books.xml');
[download]

Ron

This is exactly what I was looking for! Thank you :) I now just need to figure how to have the full nested path for each child. Thank you once again :)