Agree that it did change low level syntax. What was promised initially was that a "use v5" in a lexical scope, would switch to a Perl 5 compatible parser. This project was started, but became pre-empted by the Inline::Perl5 module, which now allows you to use 99.9% of CPAN's Perl 5 modules (even with XS components) seamlessly in Raku. And yes, that is stable enough to be used in production.