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


while( sleep 1 ) {
    my $value = int( rand 1000 );
    my $thread = 1 + int rand( 2 );
    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" );
}

__END__
C:\test>t-cond-2.pl
1:locking sem
Thread 1 terminated abnormally: lock can only be used on shared values at C:\test\t-cond-2.pl line 11.
2:locking sem
Thread 2 terminated abnormally: lock can only be used on shared values at C:\test\t-cond-2.pl line 11.
0:locking sem for thread 1
lock can only be used on shared values at C:\test\t-cond-2.pl line 34.
Perl exited with active threads:
        0 running and unjoined
        2 finished and unjoined
        0 running and detached