The link to Modern::Perl doesn't resolve as you expect.

The node resolves that to http://perldoc.perl.org/Modern/Perl.html, while swl's link resolves to https://metacpan.org/pod/Modern%3A%3APerl.

I can't see the original node shortcuts, so I've investigated a bit here:

mod://Modern::Perl: http://search.cpan.org/perldoc?Modern%3A%3APerl

metamod://Modern::Perl: https://metacpan.org/pod/Modern%3A%3APerl

You probably tried this:

doc://Modern::Perl: http://perldoc.perl.org/Modern/Perl.html

According to Link Shortcuts, that "links directly to a specific document by name: [doc://name]". In this case, '::' is translated to '/', or [doc://Some::Doc::Name] should point to http://perdoc.perl.org/Some/Doc/Name.html. Let's see: Some::Doc::Name: http://perdoc.perl.org/Some/Doc/Name.html. Yes!