You can not use the key obtained from Apple at the moment, see the item of Caution below.

use Net::APNS::Simple;

my $apns = Net::APNS::Simple->new(
    # enable if development
    # development => 1,
    auth_key => '/path/to/auth_key.p8',
    key_id => 'AUTH_KEY_ID',
    team_id => 'APP_PREFIX',
    bundle_id => 'APP_ID',
    apns_expiration => 0,
    apns_priority => 10,
);

# 1st request
$apns->prepare('DEVICE_ID',{
        aps => {
            alert => 'APNS message: HELLO!',
            badge => 1,
            sound => "default",
            # SEE: https://developer.apple.com/jp/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/TheNotificationPayload.html,
        },
    }, sub {
        my ($header, $content) = @_;
        require Data::Dumper;
        print Dumper $header;

        # $VAR1 = [
        #           ':status',
        #           '200',
        #           'apns-id',
        #           '791DE8BA-7CAA-B820-BD2D-5B12653A8DF3'
        #         ];

        print Dumper $content;

        # $VAR1 = undef;
    }
);

# 2nd request
$apns->prepare(...);

# also supports method chain
# $apns->prepare(1st request)->prepare(2nd request)....

# send notification
$apns->notify();

$apns->prepare(1st request)->prepare(2nd request)....

openssl pkcs8 -in APNs-apple.p8 -inform PEM -out APNs-resaved.p8 -outform PEM -nocrypt