#!/usr/local/bin/perl
use strict;
use warnings;
use IPC::Open2;
use IO::Handle;

$/ = "\r";
my $CR = "\r";
my $NL = "\n";

my @msg = ('INIT', 'STATUS', 'QUIT' );

my ($reader, $writer) = (IO::Handle->new, IO::Handle->new);
my @program_and_arguments = ('/usr/local/script/netdiag');

eval {
        open2($reader, $writer, @program_and_arguments);
};
if ($@) { 
    if ($@ =~ /^open2/) {
        warn "open2 failed: $!\n$@\n";
        return;
    }
    die;
}

select $writer;
$|++;
select STDERR;
$|++;
select STDOUT;
$|++;


print STDERR "Here 1\n";
my $req = shift @msg;
print $writer $req, $CR;
print STDERR "Here 2\n";                   # We come here, than it hangs

my $answer = <$reader>;
die "1" unless $answer;

print STDERR "SVR:$answer$NL";
[... keep up the dialog...]

print STDOUT "Done$NL";
__END__