#!/usr/bin/perl
use 5.020;
use strict;
use warnings;
use XML::Twig;

##
## This works as expected
##
my $working_xml = XML::Twig->new(
    twig_handlers => {
        '/shipment/box' => sub { _move(@_); 1; },
    },
    pretty_print => 'indented',
)->safe_parse(
<<"XML"
<?xml version="1.0" encoding="UTF-8"?>
<shipment>
    <box>
        <packing>
            <slip>potato</slip>
            <slip>pear</slip>
            <slip>peach</slip>
        </packing>
    </box>
    <box>
        <packing>
            <slip>apple</slip>
        </packing>
    </box>
</shipment>
XML
);

say "\n\n---------------------\n\n";


##
## This 'breaks', printing the final '</shipment>' tag twice
##
my $broken_xml = XML::Twig->new(
    twig_handlers => {
        '/shipment/box' => sub { _move(@_); 1; },
    },
    pretty_print => 'indented',
)->safe_parse(
<<"XML"
<?xml version="1.0" encoding="UTF-8"?>
<shipment>
    <box>
        <packing>
            <slip>potato</slip>
            <slip>pear</slip>
            <slip>peach</slip>
        </packing>
    </box>
    <box>
        <packing>
            <note>nothing here!</note>
        </packing>
    </box>
</shipment>
XML
);

# ----------

sub _move {
    foreach my $descendant ( $_[1]->descendants('slip') ) {
        $descendant->set_att('_TYPE' => 'produce');
        
        # Move the <slip> out of the <box> section
        #
        # This appears to be the problem, even though
        # this should never be reached in the second
        # document (no <slip> descendants)
        $descendant->move('before', $_[1]);
    }
    
    $_[1]->delete;
    $_[0]->flush();
    
    1;
}