#!/usr/bin/perl

use strict;
use warnings;
use lib sub {
    my $wanted=pop;
    return undef if $wanted ne 'Foo.pm';
    open my $fh, '<', \<<'.EOM' or die "D'Oh! $!\n";
# ---- Begin package code.
use strict;
use warnings;
    
package Foo;
use base 'Exporter';
our @EXPORT='bar';

sub bar {
    print "Hmmm, seems to work!!\n";
}

1;

__END__
.EOM
# ---- End package code.
    $fh;
};
use Foo;

bar;

__END__

##</code><code>##

$ perl -le 'use lib sub {$_[1]="Foo.pm"; undef}; use Anything;'
Modification of a read-only value attempted at -e line 1.
BEGIN failed--compilation aborted at -e line 1.