use strict; use warnings;
use XML::Twig;
my $twig = XML::Twig->new(
    pretty_print => 'indented',
    TwigHandlers => {
        ro => \&ssprint,
        sham => \&ssprint,
        bo => \&ssprint,
    }
);

$twig->xparse('<hi>
<ro><yo/></ro>
<sham><yo/></sham>
<bo><yo/></bo>
</hi>'
);

sub ssprint { print 'moo', $_->sprint, "\n"; }
__END__
moo
  <ro>
    <yo/>
  </ro>
moo
  <sham>
    <yo/>
  </sham>
moo
  <bo>
    <yo/>
  </bo>