package MyCode;
use strict;
use warnings;

sub run {
    # Main routine here
}

... rest of implementation here...

__PACKAGE__->run() unless caller();
1;

##</code><code>##

package Sample;
use strict;
use warnings;

use GetOpt::Long;

__PACKAGE__->run() unless caller();

sub run {
    my($should_foo);
    die "usage: Sample.pm [--foo|--bar]\n"
        unless(GetOptions('foo' => \$should_foo,
                          'bar' => \$should_bar);
    my $value = $should_foo ? foo() : bar();
    print  $value;
}

sub foo {
    return "Foo to you too\n";
}
sub bar {
    return "The best bar none\n";
}

1;

##</code><code>##

use Test::More tests=>1;
use Test::Exception;

use Sample;
is Sample->bar(), "The best bar none\n", 'bar() works';
is Sample->foo(), "Foo to you too\n", 'foo() works';

local @ARGV; # now undef
dies_ok { Sample->run() } 'no args dies as expected';
like $@, qr/^usage:/, 'got a usage message';