#! perl -slw
use strict;
use threads qw[ yield ];
use threads::shared;

sub thread {
    my $tid = threads->tid;
    my $refSem = shift;
    while( 1 ) {
        warn( "$tid: locking sem\n" );
        lock( $$refSem );
        warn( "$tid: waiting sem\n" );
        cond_wait( $$refSem );
        print "$tid: got: $$refSem";
        warn( "$tid: yielding\n" );
        yield;
        warn( "$tid: looping\n" );
    }
}

our $T ||= 2;

my @sems = map{ my $var :shared; \$var } 0 .. $T;
my @threads = map{
    threads->create( \&thread, $sems[ $_ ] );
} 1 .. $T;

while( 1 ) {
    my $value = int( rand 1000 );
    my $thread = 1 + int rand( $T );
    my $refSem = $sems[ $thread ];
    warn( "0: locking sem for thread $thread\n" );
    lock( $$refSem );
    warn( "0: Setting sem[ $thread ] to $value\n" );
    $$refSem = $value;
    warn( "0: signalling sem[ $thread ]\n" );
    cond_signal( $$refSem );
    warn( "0: Sleeping\n" );
    yield;
}