I need csv format so I can make sense of what happened by sorting and browsing in Excel. There are usually 5000-10,000 rows but a hopefully small number of problems.

From your suggestion I could log free format and then at the end sort each line of the logfile into the desired order.

I'm already loading each data point into a hash and then using a subroutine to print the hash in order. Since I already have a hash I don't see how that would help.