use Library;

$| = 1;
Library::createProcess('second application');


##</code><code>##

use Library;
select((select(STDOUT), $|=1)[0]);

print STDOUT  "Out  \n";
print STDERR  "   -> Err \n";
print STDOUT  "Out  \n";
print STDERR  "   -> Err \n";
print STDOUT  "Out  \n";
print STDERR  "   -> Err \n";

Library::createProcess('random application');

##</code><code>##

use IO::Select;
use IPC::Open3;

sub createProcess($path) {
   my $pid = open3(*CMD_IN, *CMD_OUT, *CMD_ERR, $path);
   my $selector = IO::Select->new();
   $selector->add(*CMD_ERR, *CMD_OUT);

   _parseStreams($selector);

   close(CMD_IN) or die "Unable to close STDIN: $!";
   close(CMD_OUT) or die "Unable to close STDOUT: $!";
   close(CMD_ERR) or die "Unable to close STDERR: $!";

   waitpid($pid, 0) or die "Waitpid failed: $!";
}


sub _parseStreams ($) {
    my($selector) = @_;
    my(@ready, $fh, $line);

    while(@ready = $selector->can_read()) {
         foreach $fh (@ready) {
            if(fileno($fh) == fileno(CMD_ERR)) {
                $line = scalar <CMD_ERR>;
                print STDERR $line;

            }
            else {
                $line = scalar <CMD_OUT>;
                print STDOUT $line;
            }

            $selector->remove($fh) if eof($fh);
        }
   }
}

##</code><code>##

Out
Out
Out
    -> Err
    -> Err
    -> Err