load is a Perl module to control when subroutines will be loaded.
use load; # default, same as 'autoload'
use load 'autoload'; # export AUTOLOAD handler to this namespace
use load 'ondemand'; # load subroutines after __END__ when requested, default
use load 'now'; # load subroutines after __END__ now
use load (); # same as qw(dontscan inherit)
use load 'dontscan'; # don't scan module until it is really needed
use load 'inherit'; # do NOT export AUTOLOAD handler to this namespace
The "load" pragma allows a module developer to give the application developer more options with regards to optimize for memory or CPU usage. The "load" pragma gives more control on the moment when subroutines are loaded and start taking up memory. This allows the application developer to optimize for CPU usage (by loading all of a module at compile time and thus reducing the amount of CPU used during the execution of an application). Or allow the application developer to optimize for memory usage, by loading subroutines only when they are actually needed, thereby however increasing the amount of CPU needed during execution.
The "load" pragma combines the best of both worlds from AutoLoader and SelfLoader. And adds some more features.
In a situation where you want to use as little memory as possible, the "load" pragma (in the context of a module) is a drop-in replacement for AutoLoader. But for situations where you want to have a module load everything it could ever possibly need (e.g. when starting a mod_perl server in pre-fork mode), the "load" pragma can be used (in the context of an application) to have all subroutines of a module loaded without having to make any change to the source of the module in question.
So the typical use inside a module is to have:
in the source. And to place all subroutines that you want to be loadable on demand after the (first) __END__.
If an application developer decides that all subroutines should be loaded at compile time, (s)he can say in the application:
use load 'now';
This will cause the subroutines of Your::Module to all be loaded at compile time.