add_filter('search_rewrite_rules', '_create_rewrite_rules');
add_filter('query_vars', '_add_query_var');

define('MYRULE', 'something');

	function _create_rewrite_rules($rewrite) {
		global $wp_rewrite;
		
		// add rewrite tokens
		$token = '%' . MYRULE . '%';
		$wp_rewrite->add_rewrite_tag($token, '(.+)', MYRULE . '=');
	    
		$keywords_structure = $wp_rewrite->root . MYRULE . "/$token";
		$keywords_rewrite = $wp_rewrite->generate_rewrite_rules($keywords_structure);
		
		return ($rewrite + $keywords_rewrite);
	}
	
	function _add_query_var($wpvar_array) {
		$wpvar_array[] = MYRULE;
		return($wpvar_array);
	}
	
	function get_token() {
		global $wp_version;
		$token = (isset($wp_version) && ($wp_version >= 2.0)) ? get_query_var(MYRULE) : $GLOBALS[MYRULE];
		return $token;
	}