It seems to me that you are fighting the tool instead of using its strength. I think it would be easier to add the buttons directly in the twig, and then printing the entire twig at once. The loop would look like this (untested):

foreach my $elt ($twig->root->descendants( '#ELT'))
  { $elt->insert_new_element( 'before', button => { attribute });}
$twig->print;
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Of course the simple answer to your question is that the xml_text_only (I hate that name!) method would do it. But really, don't use it.