what does beach season mean? Semaphore practice!

use threads;
use Thread::Semaphore;
$a={a=>'Just ',b=>'another ',c=>'Perl ',d=>'thread, '};
$s = Thread::Semaphore->new;
new threads (sub{eval{$/=abs ord($_)-96;$s->down($/);print$$a{$_};$s->up($/+1)}})->detach for reverse('a'..'d');
$s->down(5);