h2xs's inability to include constants from enums into its constant generating cycle has finally made me starting with a patch. David Nichol gave me a little piece of code that does the trick in one of his modules. Unfortunately the patterns involved the
\G assertion that I haven't understood up to this day so I had to get rid of them in order to make things work.
First tests show it works quite well. Now I have to find my way around the bleadperl source tree to see how things work together. As it looks, utilities such as h2xs don't come with tests. This is good so I don't have to change anything there. Once I have tested it with more headers and added the appropriate changes to the documentation (there's now a new switch: -e which stands for --omit-enums) I'll confront the perl5porters with a patch.
Hmmh, I wonder whether I have to patch the AUTHORS file as well to get my name into it. Damn, the most important thing is, of course, not mentioned anywhere.