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!