_ sub is superglobal

[haarg]

Using _ as a sub name is somewhat problematic, as it always refers to main::. The code makes attempts to export to _ by default, but this is almost entirely useless. The sub as defined in the module is created as main::, and even if it wasn't, () in a consuming module will always refer to main::, ignoring any imported version.

I don't think there's any real fix for this aside from using a different name, but it should at least be documented.