I would go for the twig_handlers approach. Here is something I knocked together very quickly. Note you have a missing '</list>' closing element in your XML. It doesn't produce quite the same output but I am sure you can tailor it for your own purposes.
use strict;
use XML::Twig;
use subs qw(say);
my $twig = XML::Twig->new(
twig_handlers => {
head => \&head,
para => \¶,
}
)->parsefile("foo.xml");
exit;
sub head {
my ($t, $e) = @_;
say '<h3>'.$e->text.'</h3>';
}
sub para {
my ($t, $e) = @_;
process_children($t, $e);
}
sub list {
my ($t, $e) = @_;
say '<ol>';
process_children($t, $e);
say '</ol>';
}
sub item {
my ($t, $e) = @_;
say '<li>'.$e->text.'</li>';
}
sub process_children {
my ($t, $e) = @_;
map {
if ($_->is_text()) {
say $_->text;
} else {
&{\&{$_->gi}}($t, $_) if exists &{$_->gi};
}
} $e->children();
}
sub say {
return print 'TX ', @_, "\n";
}