Code

• Data::Phrasebook
• Class::Phrasebook

Articles

• The Phrasebook Design Pattern (perl.com article)
• The Phrasebook Pattern by Yonat Sharon and Rani Pinchuk (PDF)

Books

• Design Patterns Explained by Alan Shalloway & James Trott (Addison Wesley, 2004, ISBN 0321247140)
• Design Patterns by Erich Gamma, Richard Helm, Ralph Johnson & John Vlissides (Addison Wesley, 1995, ISBN 0321247140)