Perl has supported whitespace and comments in regular expressions since approximately forever. Just use the /x modifier. All that Raku did was make that flag a default.
The same thing is available in many other languages. They copied it when they copied from Perl. For example Python's https://docs.python.org/3/library/re.html#flags documents that re.X, also called re.VERBOSE, does the same exact thing.
The fact that people don't use it is because few people care to learn regular expressions well enough to even know that it is an option. One of my favorite examples of astounding people with this was when I was writing a complex stored procedure in PostgreSQL. I read https://www.postgresql.org/docs/current/functions-matching.h.... I looked for flags. And yup, there is an x flag. It turns on "extended syntax". Which does the same exact thing. I needed a complex regular expression that I knew my coworkers couldn't have written themselves. So I commented the heck out of it. They couldn't believe that that was even a thing that you could do!
I think it's fair to say(?) that Larry's adoption of regex as a first class aspect of perl was one of its unique strengths. My opinion is that none of the subsequent languages (Python, Go, Rust, etc) that incorporated regex really embraced it - was more of a bolt on. So there has been a syntactic barrier to incorporate or improve regex within those languages. Not so with Larry's raku which had the vision to build on the perl basis and to address many of the inconsistencies that have been baked in elsewhere.
I was a full time perl coder with plenty of regex back in the day and never appreciated that (sorry) - so maybe making it the default is a good call
PS. raku has added quite a lot to the regex facilities we are familiar with, not least a straight line to using them in Grammars with rule and token methods that give you control over handling of whitespace in the target
The same thing is available in many other languages. They copied it when they copied from Perl. For example Python's https://docs.python.org/3/library/re.html#flags documents that re.X, also called re.VERBOSE, does the same exact thing.
The fact that people don't use it is because few people care to learn regular expressions well enough to even know that it is an option. One of my favorite examples of astounding people with this was when I was writing a complex stored procedure in PostgreSQL. I read https://www.postgresql.org/docs/current/functions-matching.h.... I looked for flags. And yup, there is an x flag. It turns on "extended syntax". Which does the same exact thing. I needed a complex regular expression that I knew my coworkers couldn't have written themselves. So I commented the heck out of it. They couldn't believe that that was even a thing that you could do!