RegisterController.php

<?php

// [...]

/**
 * Perform the confirmation of the user's e-mail address.
 * 
 * @param User $user The provided user instance
 * @param $token string The provided confirmation token
 * @return mixed
 */
public function confirm(User $user, $token) {
    if ($user->confirm($token)) {
        $message = 'You successfully confirmed your e-mail address.';
    } else {
        $message = 'Your e-mail address is either already confirmed or your confirmation token is wrong.';
    }

    return redirect()->route('login')->withMessage($message);
}

// [...]