It's a convoluted algorithm, that's for sure. And what else is sure is that someone has probably solved it already. There is, as mentioned, modules that can sort using the disk (Sort::External), though that says that it keeps everything in a scalar, and you really want your rows parsed - no problem, you can reparse them. Er, that seems like a waste ;-)

Personally, my preferred manner of accessing CSV files is via DBD::CSV. In this case, I'd just use "SELECT * FROM darkint ORDER BY COL9, COL32, COL33" (with some other minor setup required - making "darkint" point to "darkint.csv", setting up the column names if they aren't in the file's first line, and possibly setting the EOL character). I think those guys have solved this problem. If not, I'd then use it as an excuse to populate a real DBMS, and, with little change, be able to continue using DBI to get my data ;-)