my $h = HTTP::Headers->new;
$h->authorization_basic('user','passwort_im_klartext');
my $request = HTTP::Request->new(
    'GET',
    'http://www. ... .de/script',
    $h,
);
my $id1 = $async->add($request);
my $id2 = $async->add( HTTP::Request->new(GET => 'http://www. ... .de'));
while ( my ( $response, $id ) = $async->wait_for_next_response ) {
    say $id.' liefert '.length($response->decoded_content)." Byte: '".$response->decoded_content."'";
}