Cause: Using the -D argument to logconv.pl is supposed to use the given directory to create the temporary files. logconv.pl was writing a large amount of data in files in /var/tmp instead of the argument given to -D.
Consequence: Could fill /var/tmp.
Fix: The Berkeley DB tied perl arrays were causing this behavior. The fix is to get rid of arrays as much as possible, and get rid of all tied arrays.
Result: /var/tmp is not in danger of filling up, the directory specified with -D is used, performance is much faster, disk usage is much less.