Also consider whether it would be advantageous to, say, put the data into an SQLite database file.   As long as you are careful to use transactions (which tells SQLite that it is permitted to use lazy-writes), the tool works splendidly.   Plus, it runs on absolutely everything, requires no server, and is not specific to Perl or any other programming language.   Honestly, it’s good enough to make you swear off of “flat files” forever.