Yes, on use/require perl checks whether $INC{<modulepath>} exists (<modulepath> being e.g. "My/Module/Namespace") and if so does not attempt to load the module again. This behaviour can be conveniently exploited when mocking modules (see chromatic's MockObject tutorial for more on this).

Update: note, this does not mean that the original module's code only gets run once, so e.g. if your Config module loads a configuration file it will still reload that file every time the module is called. It just means that the module's .pm file only gets loaded once and the code isn't duplicated in memory.


There are ten types of people: those that understand binary and those that don't.

In reply to Re^3: Sharing Namespaces by tirwhan
in thread Sharing Namespaces by skazat

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