package ForeignModule;
sub NEXT { print scalar caller }
1;

##</code><code>##

package Foo;
# there is no do_something
sub import {
    my $target = caller;
    no strict 'refs';
    *{"$target:\:do_something"} = \&ForeignModule::NEXT;
}
1;

##</code><code>##

package main;
use strict;
use warnings;

use Foo;
do_something();