Note that your fastest case is also the only one that doesn't handle long lines. I find it a pretty poor benchmark to reimplement a module's logic badly and then wonder if it runs faster. Fix the 'rawio' case to handle things as well as File::ReadBackwards (and the other cases) do(es) and it'll be closer in speed. I'm sure it will still be faster, since it doesn't use tied handles or actually deal with a general purpose problem.

But I'd still use File::ReadBackwards or "tail" since I don't find "get last line of a file" to be something I care to heavily optimize on the few occasions when I do it and the code to properly handle all of the boundary cases is not something I care to maintain on its own.