When using mod_perl2 and CGI.pm (I'd rather not, but I'm working with code that is unfortunately dependent upon both), it is often the case that any fatal error (die or croak) will just stop. No warning, no error, just a blank page. I spent an hour tracing this down to a mysterious Fh line in CGI.pm that seems to cause the problem.
I'm now working on migrating the very large system in question away from CGI.pm, but it's not easy. mod_perl2 is frustratingly unsupported by the many modules that would make such a migration much easier.