Replicating your production environment for testing/debugging is not just a good idea. It is essential.

As for good ways of spying on your code - I wrote Sub::WrapPackages for just that reason. It is itself a wrapper around Hook::LexWrap, but wraps whole packages instead of individual subroutines. Writing the necessary wrapper to log subroutine entry/exit etc is left as an exercise for the reader. I have code for it, but haven't got round to CPANning it. Or you might write something similar using Aspect. Also of interest may be Devel::Trace or Devel::TraceFuncs. I've not used the latter myself, and I don't know how mod_perl-friendly they are.