GetOptions( 'test=s' => \$option_test )
    or exit(1);

defined($option_test)
    or die("Missing argument -t");

##</code><code>##

GetOptions( 'test=s' => \$option_test )
    or die("Invalid command-line option\n");

defined($option_test)
    or die("Missing argument -t\nInvalid command-line option\n");

##</code><code>##

use File::Basename qw( basename );

sub help {
    my $prog = basename($0);
    print("usage: $prog -t [options]\n");
    exit(0);
}

sub usage {
    my $msg = shift || '';
    my $prog = basename($0);
    die("${msg}Use $prog --help for help\n");
}

GetOptions(
    'help|h|?' => \&help,
    'test=s'   => \$option_test,
)
    or usage();

defined($option_test)
    or usage("Missing argument -t\n");