use XML::Rules;

my $parser = XML::Rules->new(
	rules => [
		_default => 'content',
		book => sub {
			my $title = delete $_[1]->{title};
			delete $_[1]->{'_content'};
			$title => $_[1],
		},
		bookstore => 'pass no content',
	]
);

my $data = $parser->parse(\*DATA);

use Data::Dumper;
print Dumper( $data);

__DATA__
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
...