Thanks for your response.

DBD::CSV? probably. My code just has "use DBI;"

Current system is Linux FC3 and will be migrated to latest CentOS in the near future.

I've determined that flock() is not reliable on this system. All files in question are accessed only from library routines, and switching from direct Perl functions to read, to the DBI, definitely made a difference.

As you suggest, moving to a real DB may be required. It was being considered for some time.