My experience with MS-Access leads me to believe that generating a new CSV file, in the format you want, is up to several orders of magnitude faster than inserting using DBI directly to insert every item into the database, one by one: a few seconds for generating the text files, as opposed to many minutes using DBI, for tables of a few ten thousands of records.

So, As a generic approach, I'd advice you to generate the flatfiles with perl, and use the database's loader/import mechanism to actually read the data into the database.

Note that reading all the data out of the database using Perl+DBI isn't nearly as slow as inserting/updating the records.

update I notice that jdtoronto, based on his own, independent experiences, came to the same conclusion (point 3).