The Solution: YAML

Configure our custom Mapper in our YAML file:

---
source_connection:
  base_class: New::DBI
  db_name: dbi:mysql:new
  username: user
  password: password
target_connection:
  base_class: Legacy::DBI
  db_name: dbi:mysql:legacy
  username: user
  password: password
entities:
  TransGaming::Legacy::DBI::Games:
    target_cdbi_class: TransGaming::DBI::Game
    mapper:
      class: TransGaming::DataMigration::Legacy::Mapper::GamesToGame
    mappings:
      game_name:
        target_key: name
      game_keywords:
        target_key: search_data
      game_url:
        target_key: website
      game_genre:
        target_key: game_type
        mapping:
          class: Class::DBI::DataMigration::Mapping::HasAToHasA
          config:
            target_class: New::DBI::GameType
            target_class_search_key: name
            matching_source_key: game_genre->game_genre_name
      game_vendor:
        target_key: publisher
        mapping:
          class: Legacy::Mapping::GameVendorToPublisher