#!/usr/bin/perl
use warnings;
use strict;
use constant EXECUTE => 1;
use constant WRITE => 2;
use constant READ => 4;

my $Permissions = 0;
$Permissions |= READ; # Set READ to true
$Permissions |= WRITE; # Set WRITE to true
$Permissions &= ~READ; # Set READ to false
$Permissions ^= EXECUTE; # Toggle EXECUTE
print $Permissions, "\n";

##</code><code>##

if ($Permissions & READ) {
    print "You can read.\n";
} else {
    print "You can't read.\n";
}