As I said elsewhere in this thread, Inline::Perl5 hasn't been tested against all 130,000 modules on CPAN to my knowledge, but, based on what I know of the tech and its 100% success rate so far, I'm going to assume until I hear otherwise that it already works, or will do so this year, for the vast majority.

In the unlikely event there's a module that doesn't work, then yes, you have to learn and wield a new language that isn't backwards compatible. But it is Perlish, and it is designed to coexist beautifully with Perl 5.