use strict;
use warnings;
use IPC::Open2;

$|=1;
$SIG{PIPE} = sub { print STDERR "SIGPIPE received\n"; exit; };
my $pid = open2(my $reader, my $writer, "perl echo2.pl");
print "pid=$pid\n";

print $writer "$_\n" for (qw(first second third ));
print "Data written\n";
print $writer chr 4; #try manually send EOF - didn't work!
close $writer;       #reader still "hangs"

print "Reading from pipe:\n";
while( my $in=<$reader>) {
    print  "Received: ".$in."\n";
}
close $reader;
print "No more data\n";
waitpid($pid, 0);
print "Finished\n";

=echo2.pl
#!/usr/bin/perl -w
use strict;

$|++;
print "first test line\n";
while (<STDIN>){print;}
=cut

__END__
C:\TEMP>perl ipc_open2.pl
pid=5688
first
second
third
Data written
Reading from pipe:
Received: first test line

Received: first

Received: second

Received: third
####now hung up in reader ###
#### for some reason it doesn't see that input pipe
#### closed

##</code><code>##

use strict;
use warnings;
use IPC::Open2;

$|=1;   # this is for main program
        # $writer is alread unbuffered by open2
my $pid = open2(my $reader, my $writer, "perl echo2.pl");
print "pid=$pid\n";

for ( qw(first second third) )
{
   print $writer "$_\n";   # one line in, one line out
   my $result = <$reader>;
   print $result;
}

=heading #### echo2.pl #####
#!/usr/bin/perl -w
use strict;

$|=1;
while (my $in=<STDIN>){print $in;}
print STDERR "out of loop\n";  #never gets here!
=cut  #### echo2.pl #####

__END__
C:\TEMP>perl ipc_open2.pl
pid=3244
first
second
third