This module allows you to specify those constants that should be
 documented in your POD, and pull them out a run time in a fairly
 arbitrary fashion.
 .
 Pod::Constants uses Pod::Parser to do the parsing of the source file.
 It has to open the source file it is called from, and does so directly
 either by lookup in %INC or by assuming it is $0 if the caller is
 "main" (or it can't find %INC{caller()})