I think we are getting off of the issue of the OP (Original Post). I was a bit sloppy in terminology. Ok.

I could not find any difference in behavior in the 2 lines of code that are relevant to OP's post as regards to: "-w" vs "use warnings;".

If we want to get into exactly how the "-w command line option" and "use warnings;" differ, then I would suggest that a new thread get started. For folks who want to know more, here are a couple of links: -w vs use warnings and use warnings;.

I think that we are getting "off topic".
My main point is that the attribute "RaiseError" does work and I suspect that it didn't because the statement that set that did not work. I have been unable to find any other scenario in my testing.

Now of course there could be a situation that I haven't found, but I'm reporting 2 lines of code and asking the OP to run my code. The "-w" or "use warnings;" issue is minor and does not affect my test results; having said that, I test all my code with the command line -w version.