Should this be reported as a bug?
I understand the "why" and there definitely isn't a big need for this type of functionality. However, the RHS of a regex should behave like any other eval block in my opinion.
The last time I found a bug you reported it for me. Should this one be reported as well?
I only discovered this while helping someone else on a different forum, so I don't foresee any lost sleep for anyone if this isn't fixed. It also might introduce new problems given there is a "work around" that might've used by others in the past. Can't say which action would be best.