protected function _pre($str) {
		$str=preg_replace('/(?<=^|\n)(?: {4}|\t)(.+?(?:\n+|$))/','\1',
			$this->esc($str));
		return strlen($str)?
			('<pre><code>'.
				$this->esc($this->snip($str)).
			'</code></pre>'."\n\n"):
			'';
	}