How do you define "execution time"? Do you want to know raw CPU time the script takes? If you are on a *nix platform, you can simply 'time script' which will give you Real, User, and System CPU time (IIRC) taken by the script.

If you want more profiling information, then you need to use a profiling tool. Devel::DProf is great for this. As far as "having privilege" to download modules, you could always download them and install them under you home directory as long as you set your PERL5LIB to point to the base install location. TIMTOWTDI.