package ForeignModule;
sub NEXT { print scalar caller }
=================================
package Foo;
use ForeignModule qw(NEXT);
sub do_something { NEXT(); }
sub import {
    my $target = caller;
    no strict 'refs';
    *{"$target:\:do_something"} = \&do_something;
}
=================================
package main;
use Foo;
do_something();