1. Yes, Database reads are always a bottleneck

2. Perl actually compiles into memory the code to be run, so the extra disk reads will only effect the startup speed of the script. After it has started the modules will only take a bit more memory, but not noticably.

3. I am unsure, but i do not believe Apache does anything with standard modules such as caching, but mod_perl is emadded so that does allow a speed increase.

4. Strictly Speaking, OO code is slightly slower. The function call syntax ($object->function()) takes a bit more time than the equivlant finction($object). The diffrence is very small, but does exist.

5. I know very little about SSI, but exec'ing any perl code means the Interpreter has to load into memory, read, parse, and compile the script, and then execute it. The process creation overhead of exec-like calls should make SSI slower, but i may be mistaken.