Some thoughts on various modules to do some/all of the work for you:

Could use DBD::CSV to read the source tables .. or use something like DBIx::Copy with it to do everything in one shot.

For the just-generate-the-sql method, SQL::Abstract is a handy module ..

It might also be possible w/DBD::AnyData to do it with a single cross-db SQL statement (not sure if they both need to by in-memory tables or not):

  INSERT INTO db_table ( col1, col2, col3 )
    SELECT colA, colB, colC
    FROM csv_table
  ;
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