RFC 1924 describes a compact, fixed-size representation of IPv6 addresses
 which uses a base 85 number system. Math::Base85 handles some of the uglier
 details of it.
 .
 The base 85 numbers (from 0 to 84) are as follows:
 .
 0..9 A..Z a..z ! # $ % & ( ) * + - ; < = > ? @ ^ _ ` { | } ~
 .
 At the moment, there's not much in this module. But it should be sufficient
 for the purposes of RFC 1924.
 .
 This module has a variable called $Math::Base85::base85_digits, which is a
 string containing the digits of the base 85 alphabet from lowest (0) to
 highest (~), in that order.