Do you in fact have a directory "Mapps" containing a module "Auth.pm", because as far as i now this is where Perl will look for it (e.g. current directory).
To me it really looks like Perl can not find the module at all.

You also could include a use diagnostics; in your code or take everything away but the new method and try to load the module and just call new.

I also always bless the self hash inside the new method, because otherwise you later may get an error like can't call method "auth" on unblessed reference