Cf http://www.jnthn.net/papers/2015-spw-concurrency.pdf

From pages 56 and 57:

> Perl 6 has an asynchronous looping construct called whenever ... runs whenever a value arrives ... can live in a ... react block (works like entering an event loop)

  my $code = supply {
    whenever IO::Notification.watch-path($src-dir) {
      emit .path if .path ~~ /<.pm .p6> $/;
    }
  }

So now, whenever something in $src-dir changes and its path ends with '.pm' or '.p6' that path will be emitted -- which in this case means it'll be pushed to any construct pulling from $code. Such as:

  react {
    whenever $code -> $path {
      say "Code file $path changed!";
    }
  }

This is probably the most interesting link in this entire thread.

The "react" keyword is just a channel subscription, and inside it has a pattern matcher. Channels are first-class citizens, and you're encouraged to chain channels rather than falling into callback hell. It's like Go and Ruby had a child.

If anything piqued my interest in Perl 6, it was this.

INTERCAL finally weeps for joy at being able to claim Perl 6 as a spiritual descendant.

Nice to know I'm not the only one who thought that. Now they just need the PLEASE keyword.

That construct reminds me most of callbacks: you define some code, and register it to be called in certain circumstances.