There's no point in flocking a file that you destroy before you obtain a flock.
Thanks for your comments. From what I learned in Order of flock and open, I cannot lock the file before I open (and destroy) it.
Here, I was flocking the file to handle the case where two users submit the form data at the same time. I tried using flock with a test script and it seems to protect the temp file as it's being written. Won't that happen in this script as well? (I know what I'm observing, but my test conditions are fairly controlled. I'm happy to defer to your experience.)