Auth.pm error

Use of uninitialized value in concatenation (.) or string at Bugzilla/Auth.pm line 47.
Can't locate Bugzilla/Auth/Login/.pm in @INC (@INC contains: . lib/i686-linux-thread-multi lib /usr/lib/perl5/site_perl /usr/share/perl5/site_perl /usr/lib/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib/perl5/core_perl /usr/share/perl5/core_perl) at Bugzilla/Auth/Login/Stack.pm line 45.