    protected function evalExpression($expr) {
        $var = null;
        $result = eval("\$var = $expr;");
        if ($result === false) {
            throw new HTMLPurifier_VarParserException("Fatal error in evaluated code");
        }
        return $var;
    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.