# Setup
my @ok;
++$ok[$_] for 1, 2, 3;

# Sample usage
if ($ok[$variable]) {
   ...
}

##</code><code>##

# Setup
my %fruit;
++$fruit{$_} for qw( apple banana orange );

# Sample usage
if ($fruit{$object}) {
   ...
}

##</code><code>##

# Setup
my %dispatch = (
   colour => \&area_fill,
   scale  => \&scale_image,
   warp   => \&warp_image,
);

# Sample usage
if ($handler = $dispatch{$command}) {
   $handler->();
} else {
   die("Invalid command $command\n");
}