First I second what haukex said. If you have a library, a perl module, test what this module exports. The cli is just an interface.

Second: your example is not a modulino. A modulino is a perl module .pm file that can be invoked as a program via a trick. A modulino should end with the famous 1; or cannot be loaded.

If your is a modulino you can use it in your testing program and play with their subs, testing them as you wish.

In both cases, modulino or standalone script, you can test it somehow, using Capture::Tiny (without embarking yourself in a fight with Run3 modules.. ;). you can also launch the script and inspect the exit values.

Few example I have in some test on github something you can adapt:

use strict;
use warnings;
use Test::More;
use Test::Exception;
use Capture::Tiny qw(capture);

...

# expected death
my ($out, $err, @res) = capture {
        dies_ok { a_sub_that_dies() } 'expected to die without argumen
+ts';
};

# verbosity check
($out, $err, @res) = capture {
        $obj->method( verbose => 2 );
};
ok ((split "\n", $out) > 30 , "30+ lines expected with verbosity = 2")
+;

# checking exit status (you can check 'perl your_modulino_or_script ar
+g1 arg2..' )
my $exit = system "$program /? >nul 2>&1";
ok ( 16 == ($exit>>8), "[$program /? >nul 2>&1] returned the expected 
+value");
[download]

See also testing in my bibliotheca and Test::Script from CPAN.

L*