mojo_time_promise.pl

use Mojo::Base -strict;
use Mojo::IOLoop;

my $promise = Mojo::IOLoop->delay;
Mojo::IOLoop->timer(2 => sub{ $promise->resolve(2) });

$promise->then(sub{
  my $waited = shift;

  my ($t1, $t3) = map { Mojo::IOLoop->delay } 1..2;
  Mojo::IOLoop->timer(1 => sub{ $t1->resolve(1 + $waited) });
  Mojo::IOLoop->timer(3 => sub{ $t3->resolve(3 + $waited) });

  $t1->all($t3);

})->then(sub{ say "Done after $_[-1][0] seconds." })->wait;