Thank you for your reply.

Unfortunately, I am not able to do much debugging because this is happening on a live project on a customer's web server which belongs to an ISP. My customer doesn't want me to make debugging changes to the script while the project is going on.

So far, I'm unable to reproduce the problem on my own web servers. This leaves me to discuss theory and such, which is what brought me here.

What makes it more difficult is it appears to happen when there a lot of simultaneous submissions. I will ask but I don't think I will even be able to copy a test script to their web server and test many simultaneous form submissions.

I guess I could show some code, but I'm looking to get a better understanding of flock -- beyond all that is available online and in the Perl Cookbook and Programming Perl books.

Richard