It does refer to the file name (save for the fact that it's dots instead of dashes and has no file extension). In the case of `std/datetime/package.d` (which has the module identifier of `std.datetime`), `Runtime.args[1]` gives you `std.datetime.package`, whereas it needs to be `std.datetime` (because that's the actual module name). So, this change takes the `.package` off the end. It's a downside to Walter's decision to make it so that `package.d` files end up with the module name matching their package name rather than having package in their name.