In mod_perl 2.0, several configuration directives were renamed or removed. Several APIs also were changed, renamed, removed, or moved to new packages. Certain functions, while staying exactly the same as in mod_perl 1.0, now reside in different packages. Before using them, you need to find and load the new packages.
Since mod_perl 2.0 hasn't yet been released as of this writing, it's possible that certain things will change after the book is published. If something doesn't work as explained here, please refer to the documentation in the mod_perl distribution or the online version at http://perl.apache.org/docs/2.0/ for the updated documentation.
Eric Cholet (Logilune) and
Stas Bekman (StasoSphere & Free Books).