I just tried that ModPerl::RegistryPreforkCustom and the call trace isn't as complete which makes sense because I'd be checking it sooner.

Line 207 of file /usr/lib/perl5/ModPerl/RegistryCooker.pm called ModPerl::RegistryPreforkCustom::error_check
Line 170 of file /usr/lib/perl5/ModPerl/RegistryCooker.pm called ModPerl::RegistryCooker::run
Line 19 of file /usr/lib/perl5/ModPerl/RegistryPrefork.pm called ModPerl::RegistryCooker::default_handler
Line 0 of file -e called ModPerl::RegistryPrefork::handler
Line 0 of file -e called (eval)

vs ($SIG{DIE))

Line 11 of file /home/mlenz/mlenz.domain.com/cgi-bin/details called main::__ANON__
Line 204 of file /usr/lib/perl5/ModPerl/RegistryCooker.pm called ModPerl::ROOT::ModPerl::RegistryPreforkCustom::home_mlenz_mlenz_2edomain_2ecom_cgi_2dbin_details::handler
Line 204 of file /usr/lib/perl5/ModPerl/RegistryCooker.pm called (eval)
Line 170 of file /usr/lib/perl5/ModPerl/RegistryCooker.pm called ModPerl::RegistryCooker::run
Line 19 of file /usr/lib/perl5/ModPerl/RegistryPrefork.pm called ModPerl::RegistryCooker::default_handler
Line 0 of file -e called ModPerl::RegistryPrefork::handler
Line 0 of file -e called (eval)

Looks like I'd need to subclass the cooker instead and override one or more of the other methods.