use strict;
use XML::Rules;

my $parser = XML::Rules->new(
  normalisespaces => 1,
  rules => {
	div => sub {
		if (exists $_[1]->{class}) {
			my $class = delete $_[1]->{class};
			return '@'.$class => $_[1];
		} else {
			return $_[0] => $_[1];
		}
	}
  },
);

my $data = $parser->parse(\*DATA);
use Data::Dumper;
print Dumper($data);

__DATA__
<div id="main">
<div class="A">
	...
</div>
<div class="A">
	...
</div>
<div class="A">
	...
</div>
<div class="B">
	...
</div>
<div class="B">
	...
</div>
<div class="B">
	...
</div>
</div>