in reply to CGI::Appl can't find sub

It seems likely that adding the subroutine call altered the scope of Asub2. Perhaps you deleted a closing curly brace or a semi-colon?

Are you using warnings and strict? What does perlcritic say? When you use perl-tidy, is Asub3 indented the way you think it should be?

If you aren't using these tools to analyze your problem, is there a reason for skipping them?

As Occam said: Entia non sunt multiplicanda praeter necessitatem.