function clear($key) {
		if (!$this->dsn)
			return;
		$ndx=$this->prefix.'.'.$key;
		$parts=explode('=',$this->dsn,2);
		switch ($parts[0]) {
			case 'apc':
			case 'apcu':
				return call_user_func($parts[0].'_delete',$ndx);
			case 'redis':
				return $this->ref->del($ndx);
			case 'memcache':
				return memcache_delete($this->ref,$ndx);
			case 'memcached':
				return $this->ref->delete($ndx);
			case 'wincache':
				return wincache_ucache_delete($ndx);
			case 'xcache':
				return xcache_unset($ndx);
			case 'folder':
				return @unlink($parts[1].$ndx);
		}
		return FALSE;
	}