"For example it wasn't until Switch.pm was pulled into the core that it could be done without source filters." Not true, actually - it could comfortably be don

"For example it wasn't until Switch.pm was pulled into the core that it could be done without source filters." Not true, actually - it could comfortably be done with Devel::Declare - we just haven't had time to yet. (I wrote Devel::Declare and in fact have been trying for about a year to persuade somebody to write me the smartmatch logic for perl5 v8 with a promise that I'll do the given/when syntax if somebody does ...) Source filters fail because they're line-by-line; Devel::Declare is still effectively a filter in some respects but it's one that co-operates with the tokenizer so it tends not to interact badly with anything. If you've seen places it does, failing tests would be very welcome.