>2. Modules

This speed hit is only taken if you don't preload your modules. All used modules should be loaded in your apache startup. Then, they will be compiled only once. The memory (mostly) doesn't even need to be copied, it uses shared memory with copy-on-write, so it is very very fast. There is not a speed difference in loading a pre-loaded Perl module in mod_perl versus loading a C library. However, this can use a lot of RAM. I've had sites where there were two apaches, one for mod_perl, another for everything else, the mod_perl version used 6 megs per process, the other used 1 meg. It was very fast for everything that way.

>3. Modules & Apache

Yes, it caches them. It evals them. Don't use mod_perl until you're read the docs long enough to understand what this does to the namespace. Really.