a.pl

use Modern::Perl;
use Mojo::UserAgent;
use Data::Dumper;

my $e = Event->new;

$e->on(
  what => sub {
    my $ua = Mojo::UserAgent->new;
    $ua->get('http://127.0.0.1:3001' => sub { warn 55 });
    warn 33;
  }
);

$e->emit('what');
warn 44;

package Event;
use Mojo::Base 'Mojo::EventEmitter';

1;