Laravel多变量子子域

Currently I have:

Route::domain('{subdomain}.alfa.example.com')->group(function () {

    Route::get('/tet', function ($subdomain) {

        dd($subdomain); 

    });
})

I want to be able to use a route that will respect the following criteria:

• {variable}.alfa.example.com
• {variable 1}. (...) .{variable N}.alfa.example.com
• Variable is not known or defined.
• N is also not defined and I can have as many dots as I can (as many sub sub domains as I can)

Before asking, I have tried to use ->where('subdomain', '(.*)'); but with no effect.

Route::domain('{subdomain}.alfa.example.com')->group(function () {

    Route::get('/tet', function ($subdomain) {

        dd($subdomain); 

    })->where('subdomain', '(.*)');
});

After all I have used ->where('subdomain', '(.*)')