Well, I've had this problem countless times in many languages. The problem is that while writing a new output file, that file may not(and probably does not) exist on the hard drive yet. What's more interesting is that it takes quite some time for the file to save on the drive. Waiting for a set amount of time *may* work but more often than not, I haven't seen it make a difference, no matter how long a time is waited. What you can do is combine the two processes into one. That would rectify the situation, but I have a feeling that there's a reason for not having just one process. One solution to your problem is outputting the output of process 1 to a file (if you need it) AND/OR simultaneously using expect.pm to grab runtime data from process 1 and to use it.