gistfile1.txt

perl5:
use EV;
use Promises backend => ['EV'], qw(deferred);
use AnyEvent;

my $d1 = deferred();
my $final = $d1->promise->then(sub($r) {
  my $d2 = deferred();
  say 'GOT '.$r; # Should be TEST1

  my $timer;
  $timer = AnyEvent->timer(
      after       => 2,
      cb          => sub {
          $timer = undef;
          $d2->resolve;
      }
  );

  return $d2->promise;
})->then(sub($r) {
  say 'GOT '.$r; # Should be TEST2
});
$d1->resolve('TEST1');

my $c = AnyEvent->condvar;
collect($final)
    ->done(
        sub { $c->send(@_); },
        sub { $c->croak(@_); },
    );
$c->recv;

javascript:
var p1 = new Promise(function(resolve) { resolve('Test1') });
await p1.then((r) => {
        console.log('GOT '+r);
        return new Promise(function(resolve) { setTimeout(function(){ resolve('Test2') },2000) })
    })
    .then((r) => {
        console.log('GOT '+r)
    });
console.log("DONE")

raku:
my $p1 = Promise.new();
$p1.vow.keep("TEST1");

await $p1.then({
    say "GOT " ~ .result; # expecting TEST1
    return Promise.in(2).then: { return "TEST2" };
}).then({
    say $_.gist; # Promise, NOT "TEST2"
    say "GOT" ~ .result; # expecting TEST2, but got exception
});
say "DONE";