private function matchVariableVars(array $routeUri)
    {
        $this->vars = [];
        foreach ($routeUri as $index => $route) {
            if (!in_array($route, ['?', $this->uri[$index]])) {
                $this->vars = [];
                return; // match failed - no exact match, no variable match
            }
            if ($route === '?') { // found a variable
                $this->vars[] = $this->uri[$index];
            }
        }
    }