#!/usr/bin/perl -l
#
# main.pl
#
use strict;
use warnings;

sub foo {
  'foo';
}

sub bar {
  'bar';
}

print foo();
{
  no warnings 'redefine';
  local *foo=\&bar;
  do "inc.pl";
}
print foo();

#
# inc.pl
#
print foo();