To have the import list (here, qw(suba)) actually do something, your module needs to provide an import sub. Because A doesn't define one or inherit one, the import list is silently ignored. This has been construed as a feature :).

You do try to inherit Exporter's import(), but it fails due to an error so common that there's a specific warning just to tell you about it. As soon as you enable warnings, you'll see it.