use strict;
use warnings;

sub create_toggle {
    my $flag = 0;
    return sub { $flag = 1-$flag } # your favorite method here
}

my $toggle = create_toggle;

print $toggle->()."\n" for 1..10;

##</code><code>##

use strict;
use warnings;
{
    package Toggler;
    sub new {
	my $flag =  0;
	return sub { $flag = 1-$flag }
    }
}

my $toggle = new Toggler;

print $toggle->()."\n" for 1..10;