use IPC::Open2 qw(open2);

my $pid = open2 ">&STDOUT", my($w), 'perl -ne print' or die $!;
print "pid: $pid\n";

print {$w} "hello world! ($_)\n" for 0..9;
close $w or die $!;

print "waiting for slave process\n";
waitpid $pid, 0 or die $!