Making Perl faster

When perl is not quite fast enough

Most modules are able to export lots of their functions and other symbols into your namespace to save you typing. If you have only one argument to use, such as

use POSIX; # Exports all the defaults

then POSIX will helpfully export its default list of symbols into your namespace. If you have a list after the module name, then that is taken as a list of symbols to export. If the list is empty, no symbols are exported:

use POSIX (); # Exports nothing.

You can still use all the functions and other symbols – you just have to use their full name, by typing POSIX:: at the front. Some people argue that this actually makes your code clearer, as it is now obvious where each subroutine is defined. Independent of that, it’s faster:
use POSIX; use POSIX ();
0.516s 0.355s
use Socket; use Socket ();
0.270s 0.231s

POSIX exports a lot of symbols by default. If you tell it to export none, it starts in 30% less time. Socket starts in 15% less time.