I have a number of Perl scripts which parse insurance claims data.
Some underwriters are able to change their format EVERY time they send us some data. Worst seem to be those who send us Excel-files as it is by far too easy for them to change it: swapping some columns around; changing the column titles; adding rows with sub-totals; ... The variations are without limits and once I change a script to take into account a "new" format or they revert to a previous format. The CVS-system has saved my sanity more than once!
CountZero
"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law