perl module for sets of ordered constants like enums in C

 The enum module defines a set of symbolic constants with ordered numeric
 values ala C enum types.
 .
 It is now capable of creating ordered bitmask constants as well. See the
 BITMASKS section in the documentation for details.
 .
 What are they good for? Typical uses would be for giving mnemonic names to
 indexes of arrays. Such arrays might be a list of months, days, or a return
 value index from a function such as localtime().