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use is evaluated at compile time. Require is evaluated at run time. So Require is good if you want one module or another but the instantiation overhead of both is very large which means you want to instantiate only the one you need.

Use and Require are most common methods used to load modules.
Use:
1) It is evaluated at compile time only.
2) it is used only to load modules.
3)No need to give file extensions when we are using "use"
Require:
1)This is evaluated at Run time
2)This method is used for both libraries and modules.
3)Need to give file extensions like pl,pm etc..