...
use threads ();
use threads::shared ();
use Thread::Semaphore;
...
my $line_semi :shared = new Thread::Semaphore(0); #works in 5.8.8
...
...
 sub sendout_sub ($ $)
{
	...
       {
            $line_semi->down(1);    # line 309
            lock @xlines;
            $line = shift @xlines;
        }  #implicit unlock;
....