Be careful. The braces ({}) don't localize everything you are doing. The create a scope for your variables, but your package and subroutine declarations remain global.

No, that's wrong. package is lexically scoped. That's why you don't have to switch it back after a module changes it.

print(__PACKAGE__, "\n");
{
   package Foo;
   print(__PACKAGE__, "\n");
}
print(__PACKAGE__, "\n");
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main
Foo
main
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