protected function evaluateExpression($expr)
	{
		$original = $expr;
		foreach ($this->getOptimizationPasses() as $regexp => $methodName)
		{
			$regexp = str_replace(' ', '\\s*', $regexp);
			$expr   = preg_replace_callback($regexp, [$this, $methodName], $expr);
		}

		return ($expr === $original) ? $expr : $this->evaluateExpression(trim($expr));
	}