our @handles;
our $message = ('xxxxxxxx');

sub child
{
        my $buffer;
        while(sysread(STDIN, $buffer, 8))
        {
                print("$$: $buffer\n");
        }
}

for($i=0; $i < 4; $i++)
{
        if(!open($handles[$i], '|-'))
        {
                # child process
                child();
                exit 0;
        }
}

for($i=0; $i < 4; $i++)
{
        syswrite($handles[$i], $message);
        syswrite($handles[$i], $message);
        syswrite($handles[$i], $message);
}

for($i=0; $i < 4; $i++)
{
        close($handles[$i]);
}

Produces the following output then freezes:

18241: xxxxxxxx
18241: xxxxxxxx
18241: xxxxxxxx
18242: xxxxxxxx
18242: xxxxxxxx
18242: xxxxxxxx
18243: xxxxxxxx
18243: xxxxxxxx
18243: xxxxxxxx
18244: xxxxxxxx
18244: xxxxxxxx
18244: xxxxxxxx