use Thread::Semaphore qw( );
use threads::shared   qw( );

BEGIN {
   *sema_down = \&Thread::Semaphore::down; 
   *sema_up   = \&Thread::Semaphore::up; 
}

my $line_semi : shared = 0;

...
sema_down(\$line_semi, 1);
...
sema_up(\$line_semi, 1);