{
   package PkgA;

   # Loads the module if it's not loaded, and import "foo".
   use SomeModule qw( foo );

   foo();  # ok
}

{
   package PkgB;

   # Loads the module if it's not loaded, importing nothing.
   use SomeModule qw(  );

   foo();              # Error. No such function in PkgB
   SomeModule::foo();  # ok
}

{
   package PkgC;

   # The module might be loaded, but nothing is imported from it.

   foo();   # No such function in PkgC
}