close $w or die "close pipe[1] failed: $!";
is(<$r>, "world\n", 'read stdout of spawned from pipe');
is(waitpid($pid, 0), $pid, 'waitpid succeeds on spawned process');
close $w or die "close pipe[1] failed: $!";
is(<$r>, "world\n", 'read stdout of spawned from pipe');
is(waitpid($pid, 0), $pid, 'waitpid succeeds on spawned process');