use strict;
use warnings;

## Define a lexical variable $foo (which will be otherwise unrechable after
## the next our save by the closure)
my $foo = 'file lexical';

sub closure { print "closure says: $foo\n" }

print "before our: $foo\n";

## This masks the above lexical $foo for the rest of the outer file scope
our $foo = '$main::foo';

package One;

## And this masks the prior lexically visible $foo that pointed to $main::foo
our $foo = '$One::foo';

{
package Two;

## This $foo temporarily masks the prior $One::foo
our $foo = '$Two::foo';

print "inside package Two: $foo\n"
}

## Prior our $foo was scoped to the explicit block, so unadorned $foo
## once again means $One::foo . . .
print "back outside Two's block: $foo\n";

package main;

print "unadorned \$foo: $foo\n";

## But we can still explicitly refer to each of them by full package name
{
no strict 'refs';
print "$_: ${$_}\n" for qw( main::foo One::foo Two::foo );
}

## And now the sub closure is the only thing which has a handle on the
## original lexical $foo
closure();

exit 0;

__END__
before our: file lexical
inside package Two: $Two::foo
back outside Two's block: $One::foo
unadorned $foo: $One::foo
main::foo: $main::foo
One::foo: $One::foo
Two::foo: $Two::foo
closure says: file lexical