I'd use open, while, and close to get the data from the file. I'd use the the $var = <HANDLE>; technique to read the file (others here would disagree).

I'd use the DBI module from CPAN to do the database stuff. When you get to this point, post some code and we can nudge you along, since this is likely your first time querying a database from Perl and that's often asking a bit much from a Perl newbie.

I'd use open, foreach, and close to write the new data to the new file.