• Dynamically assume whatever values or size needed
• Can dynamically lengthen or shorten hashes
• May be defined, but empty
• No predefined size or "out of bounds" error
• New keys are auto-instantiated when used
• Old keys may be deleted

        my %wheels = (unicycle => 1,
                      bike     => 2,
                      tricycle => 3);

        $wheels{car} = 4; # Creates a new key/value pair
        $wheels{van} = 4; # Creates another new key/value pair

        delete $wheels{unicycle};