Any list you create will have to account for differences in versions. This stuff changes over time.

I think that's inexact. If you mean specific warnings move from one category to another, then a program may start spitting out previously inhibited warnings when perl is updated. This is not good behavior, and should only be done when something *big* has changed in the language (like we got it extremely wrong the first time).

If you mean new warnings are added, then yes, that's allowable. But it's not much problem for programmers, because they aren't interested in non-existent warnings.

Concerning the former, I've recently seen an library (in another language) where the error numbers are matched to error messages. However, the mapping isn't stable, but the messages (mostly) are, so error handlers parse the error messages to decide which error occurred! TIMTOWTFIU!