protected function evaluateSafenessAsURL()
	{
		$regexpInfo = RegexpParser::parse($this->vars['regexp']);

		// Match any number of "(" optionally followed by "?:"
		$captureStart = '(?>\\((?:\\?:)?)*';

		// Regexps that start with a fixed scheme are considered safe. As a special case, we
		// allow the scheme part to end with a single ? to allow the regexp "https?"
		$regexp = '#^\\^' . $captureStart . '(?!data|\\w*script)[a-z0-9]+\\??:#i';
		if (preg_match($regexp, $regexpInfo['regexp'])
		 && strpos($regexpInfo['modifiers'], 'm') === false)
		{
			$this->markAsSafeAsURL();

			return;
		}

		// Test whether this regexp could allow any character that's disallowed in URLs
		$regexp = RegexpParser::getAllowedCharacterRegexp($this->vars['regexp']);
		foreach (ContextSafeness::getDisallowedCharactersAsURL() as $char)
		{
			if (preg_match($regexp, $char))
			{
				return;
			}
		}

		$this->markAsSafeAsURL();
	}