$in_twig->parsefile('in.xml'); # ERROR, out of order
$in_twig = XML::Twig->new( # ERROR, obliterating $in_twig
                  twig_roots => { violation => 1 }, ## ERROR, 1 is not a callback
                  twig_handlers => { ## um, this goes in twig_roots
                   violation => sub { processViolation( $in_twig, $_, \%out_twigs, \%opt );
                  }