# Warnings, strict and our aren't needed if you don't 
# want to bother. I Just like to have them
use strict;
use warnings;
our $c = 5;
sub foo {
    print $c;
}

# Next line is the only thing that's different from
# what you'd have if you were going to use "do"
# A filed being required/used should return something true
1;

##</code><code>##

use Foo();
use strict;
# you couldn't call foo without () under use strict 
# if you had used "require" or "do"
foo;
our $c;
print $c;

##</code><code>##

package Foo;                 # This line is new
use strict;
use warnings;
use base qw(Exporter);       # This line is new
our @EXPORT_OK =qw($c foo);  # This line is new, stuff the caller MAY import to use it unqualified
our $c = 5;
sub foo {
    print $c;
}

1;

##</code><code>##

# Next line is different, explicitely say we want to use foo unqualified (without Foo::)
use Foo qw(foo);            
use strict;
foo;
# We could also have listed $c in the import list and then use plain $c
# But let's instead show you can still access it by qualifying 
print $Foo::c;