#!/usr/bin/env perl

use 5.010;
use strict;
use warnings;

{
	package Calc::Role::BinaryOperation;
	use Moo::Role;
	use MooX::Options;
	
	option a => (
		is             => 'ro',
		required       => 1,
		format         => 's',
		documentation  => 'first number',
	);
	
	option b => (
		is             => 'ro',
		required       => 1,
		format         => 's',
		documentation  => 'second number',
	);
}

{
	package Calc::Cmd::add;
	use Moo;
	use MooX::Cmd;
	use MooX::Options;
	
	with 'Calc::Role::BinaryOperation';
	
	sub execute {
		my $self = shift;
		say($self->a + $self->b);
		exit(0);
	}
}

{
	package Calc::Cmd::subtract;
	use Moo;
	use MooX::Cmd;
	use MooX::Options;
	
	with 'Calc::Role::BinaryOperation';
	
	sub execute {
		my $self = shift;
		say($self->a - $self->b);
		exit(0);
	}
}

{
	package Calc;
	use Moo;
	use MooX::Cmd;
	
	sub execute {
		my $self = shift;
		my ($args, $chain) = @_;
		die "Need to specify a sub-command!\n";
	}
}

Calc->new_with_cmd->execute;

##</code><code>##

$ perl calc.pl 
Need to specify a sub-command!
$ echo $?
255
$ perl calc.pl add --help
USAGE: calc.pl [-abh] [long options...]
	-a          first number
	-b          second number
	-h --help   show this help message

$ perl calc.pl subtract --a 9 --b 5
4
$ perl calc.pl add --a 9 --b 5
14
$ echo $?
0

##</code><code>##

$ git --someopt --anotheropt

##</code><code>##

$ git subcommand --someopt --anotheropt