use XML::Rules;

my $xml = <<XML;
<root>
<mynode id='500'>
</mynode>
<mynode id='500'>
</mynode>
</root>
XML

my @rules = (
  # Only get 'mynode' directly under root
  mynode => [ '/root' => sub { print "$_[1]->{id}\n"; return }, _default => undef ],
  _default => undef,
);
my $xr = XML::Rules->new(rules => \@rules);
$xr->parse($xml);