in reply to READ .dat file
as stated above, .dat isn't a format, just an extension, so you can read the file just like a regular text file.
See open, perlio, and also you can search the previous answers in the Monastery ( e.g. here ), which will give you plenty to get started on. You can also look through CPAN for the various file handling modules.
Hope this helps, let us know how you get on (remember to post any code and error messages and example data you write/get/use)