Thank you for taking the time and test it, much appreciate it.

use experimental 'signatures';

Yes, this (sub ($f = foo())) messes it up. I will add a disclaimer. Hopefully there won't be much frequency of that happening.

The module has other serious issues:

Yes, this mishandling of overloaded exception was a bug that I just resolved in version 1.1.2 now available on CPAN. Thank you again for helping me make it better!