When something goes wrong, we expect the software to report the problem. But if we don't understand the meaning of the error message, we won't be able to resolve it. Therefore in this chapter we will talk about errors specific to mod_perl, as reported by a mod_perl-enabled Apache server.
Many reports are produced by Perl itself. If you find them unclear, you may want to use the use diagnostics pragma in your development code. With the diagnostics pragma, Perl provides an in-depth explanation of each reported warning and error. Note that you should remove this pragma in your production code, since it adds a runtime overhead.
Errors that may occur during the build and installation stages are covered in the respective troubleshooting sections of Chapter 3. This chapter deals with errors that may occur during the configuration and startup, code parsing and compilation, runtime, and shutdown and restart phases.