protected function compileIfStack($expression)
    {
        foreach (['UnLess', 'If', 'ElseIf', 'ElseIfAlias', 'Else', 'EndIf'] as $token) {
            $out = $this->{'compile'.$token}($expression);

            if (strlen($out) !== 0) {
                $expression = $out;
            }
        }

        return $expression;
    }