You're always within a package.

No, you are not.

package;
print __PACKAGE__;
__END__
Use of "package" with no arguments is deprecated at ...
Use of uninitialized value in print at ...
[download]

From perldoc -f package:

If NAMESPACE is omitted, then there is no current package, and all identifiers must be fully qualified or lexicals. However, you are strongly advised not to make use of this feature. Its use can cause unexpected behaviour, even crashing some versions of Perl. It is deprecated, and will be removed from a future release.

Although you shouldn't, you can be outside of any package.