While others have commented on alternative methods to the overarching problem, I wanted to address the specific question of a 'boolean' semaphore. One 'brain-dead' simple approach would be to sub-class Thread::Semaphore such that the ->up() operation sets the semaphore to 1 rather than incrementing it. 
package Thread::Semaphore::Boolean;

use threads::shared;

use parent 'Thread::Semaphore';

# Create a new 'boolean' semaphore
sub new {
    my $class = shift;
    return $class->SUPER::new(1);
}

# Set semaphore's count to 1
sub up {
    my $sema = shift;
    lock($$sema);
    $$sema = 1;
    cond_broadcast($$sema);
}

1;

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Again, this is 'brain-dead' in that elementary uses of ->down() and ->up() will work, whereas other 'fancy' operations may break (e.g., $sema->down(2) would 'hang' because the 'boolean' semaphore would never be greater than 1).

In reply to Re: Boolean Thread::Semaphore ? by Anonymous Monk
in thread Boolean Thread::Semaphore ? by chrestomanci

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