SQL::Translator: Translate the DDL from one schema type (say, Oracle) to another (say, PostgreSQL). It can also be used to translate a schema to something completely different, such as a YAML file. One particularly nice feature is the ability to translate a schema to code. An example of this would be translating a MySQL schema to Class::DBI code. Introductory documentation is available.

Sub::Override: Instead of writing this:

  undef (local *Some::sub);
  local *Some::sub = sub { ... };

You would write:

  Sub::Override->new('Some::sub', sub { ... });

The scoping rules are (mostly) the same and it is more readable. Very useful for tests.