interleave_again.p

use Mojo::Base -strict;

use Mojo::IOLoop;

Mojo::IOLoop->timer(0 => sub { say 'zero' });

Mojo::IOLoop->delay(
  sub {
    my $delay = shift;
    my $next = $delay->pass('B')->begin;
    Mojo::IOLoop->timer(1 => sub { say 'one'; $next->() });
  },
  sub {
    my ($delay, $value) = @_;
    my $next = $delay->pass('C')->begin;
    Mojo::IOLoop->timer(1 => sub { say "two: $value"; $next->() });
  },
  sub {
    my ($delay, $value) = @_;
    my $next = $delay->pass('D')->begin;
    Mojo::IOLoop->timer(1 => sub { say "three: $value"; $next->() });
  },
  sub {
    my ($delay, $value) = @_;
    my $end = $delay->begin;
    Mojo::IOLoop->timer(1 => sub { say "four: $value"; $end->() });
  } 
)->wait;