You may want to read all the data in first then dump it out as needed. I would build a hash with the first key being the car number. The next key I would use company and then under there I would store a reference to an array holding all the dates. I am not sure what $le is but where is goes in the has depends on whether it is related to the car, the company or perhaps the car/company/date event

If you converted the dates to European format yyyy-mm-dd then you can do a simple sort on them and print out sequential pairs of dates to get the 'close' ones.

Cheers,
R.