CPAN hosts a lot of legacy modules known as backpan that do not have
an HTML landing page so use fake origin URL pattern below instead:
author corresponds to the normalized CPAN user account, not the full
author name, while module_name is the distribution name.
For instance the distribution File-ManualFlock is a backpan
so URL https://metacpan.org/dist/File-ManualFlock does not exist and returns 404.
The only HTML page we can found for this distribution is the backpan directory
for the associated CPAN user WCATLAN.
Related to T2833
Depends on D8648