You can insert new children in any part of the Tree but not using handlers. Since the new child you already inserted will not be parsed.

A good technique is to create a new node with the XML you want to insert.

my $xml = <<__XML__;
<whatever>
...
</whatever>
__XML__

my $twig2 = XML::Twig->new();
$twig2->parse($xml);
my $elt2 = $twig2->root;

$elt->insert_new_elt('first_child', 'foobar', $elt2);
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