I created Constant::Export::Lazy a while ago to consolidate the main constant exporting module at work into something even better. I've just uploaded a major release which allows for adding all the features that I can reasonably think of being useful for a lazy constant exporting module.
It can now support something like Exporter.pm's %EXPORT_TAGS, along with numerous other improvements. I also toiled a bit at it with Devel::Cover and it has 100% test coverage now. In the progress of achieving that I found a few minor bugs that I fixed.
In implementing this module I tried to avoid adding narrow specific features (like %ENV overrides, or support for %EXPORT_TAGS), and instead added more general callbacks that make those features and others I haven't even thought of yet possible.
For why I needed to write the umpteenth constant creation module on the CPAN instead of using something that already exists see the rationale in the documentation.
This module's already been stable for a while and I see no reason why I'd introduce any breaking changes to it. If you'd like an easy-to-use constant defining module that you can use in multiple mutually incompatible environments give it a shot.