pipe READOUT, WRITEOUT;
if (my $pid = fork)
{
    close(WRITEOUT);
    # try to read from READOUT, which fails.
}
else
{
    close(STDERR);
    close(STDOUT);
    open(STDOUT, ">&WRITEOUT");
    # This next line makes no difference.
    select(STDOUT); $|=1;
    exec("some_application");
}