CGI-Application sending warnings to browser

I don't think so :)

That sounds weird, are you sure you're not redirecting STDERR to STDOUT?

Or that warnings aren't enabled globally (like on shebang)?

Turn warnings off?  no warnings; or  $SIGN{__WARN__}=sub{};?

Lets go fishing grep warn CGI-Application-FastCGI-0.02 grep stderr CGI-Application-FastCGI-0.02

grep warn CGI-Application-4.50

grep stderr CGI-Application-4.50

grep warn FCGI-0.74

grep stderr FCGI-0.74

From what I can see above, none of the potential culprits are responsible for what you're seeing, and surely someone would have noticed if FCGI.... were broken so seriously

So CGI::Application is not sending warnings to browser