The following are a few other modules that you may find of use, but in this book we won't delve deeply into their details:
Apache::DumpHeaders is used to watch an HTTP transaction, looking at the client and server headers.
Apache::DebugInfo offers the ability to monitor various bits of per-request data. Similar to Apache::DumpHeaders.
Devel::StackTrace encapsulates the information that can be found through using the caller( ) function and provides a simple interface to this data.
Apache::Symbol provides XS tricks to avoid a mandatory "Subroutine redefined" warning when reloading a module that contains a subroutine that is eligible for inlining. Useful during development when using Apache::Reload or Apache::StatINC to reload modules.
Eric Cholet (Logilune) and
Stas Bekman (StasoSphere & Free Books).