foreach my $child ($obj->children()) {
    next unless $child->name eq 'paragraph';
    # code goes here
  }

##</code><code>##

  foreach my $child ($obj->children()) {
    next unless $child->name eq 'page';
    foreach my $grandchild ($child->children()) {
      next unless $grandchild->name eq 'header';
      # code goes here
    }
  }

##</code><code>##

  foreach my $para ($obj->match('paragraph')) {
    # code goes here
  }

##</code><code>##

  foreach my $header ($obj->match('/page/header')) {
    # code goes here
  }