Declaring constants is very convenient for writing programs, but as
they're often inlined by Perl, retrieving their symbolic names can be
tricky.  This is made worse with low level modules that use constants for
bit-twiddling.

Devel::Constants makes this much more manageable.

It silently wraps around the constant module, intercepting all constant
declarations.  It builds a hash, associating the values to their names.
The names can then be retrieved as necessary.