> date -u | perl stdin-pipe.pl --opt X
$VAR1 = {
          'Initial, opt' => 'X'
        };

Any option argument will be abandoned; collecting STDIN ...
$VAR1 = {
          ' ...after collecting STDIN, opt' => 'Wed May  3 05:44:43 UTC 2023
'
        };

$VAR1 = {
          'Final, opt' => 'Wed May  3 05:44:43 UTC 2023
'
        };