POE provides a framework for this kind of thing and much much more:

  2006/04/20 10:57:59 sub10
  2006/04/20 10:57:59 sub15
  2006/04/20 10:58:09 sub10
  2006/04/20 10:58:14 sub15
  2006/04/20 10:58:19 sub10
  2006/04/20 10:58:29 sub10
  2006/04/20 10:58:29 sub15

use POE;
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init($DEBUG);

POE::Session->create(
    inline_states => {
    _start  => sub {
      $poe_kernel->yield("sub10");
      $poe_kernel->yield("sub15");
                   },
    sub10 => \&sub10,
    sub15 => \&sub15,
});

$poe_kernel->run();

sub sub10 {
    DEBUG "sub10";
    $poe_kernel->delay("sub10", 10);
}

sub sub15 {
    DEBUG "sub15";
    $poe_kernel->delay("sub15", 15);
}
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