XOTcl

Dynamic Object Aggregations
An article about the usage of dynamic object aggregations as a foundation for composition.
http://www.acm.org/conferences/sac/sac2000/Proceed/FinalPapers/PL-18/

Enhancing Object-Based System Composition through Per-Object Mixins
The paper introduces per-object mixins as a new object-level language construct for object-based system composition. Per-object mixins are implemented in the scripting language XOTCL as a straightforward extension of its method chaining mechanism and enables the developer to mix classes into the precedence order of an arbitrary object. [PDF]
http://wwwi.wu-wien.ac.at/~uzdun/publications/xotcl-mixin.pdf

Filters
Article by Gustaf Neumann and Uwe Zdun about filters as a language support for design patterns in object-oriented scripting languages.
http://www.usenix.org/publications/library/proceedings/coots99/full_papers/neumann/neumann_html/

XOTcl: Extended Object Tcl
Official home page. Information, history, source and binary downloads, publications.
http://media.wu-wien.ac.at/

XOTclIDE
XOTcl Integrated development environment, inspired by Smalltalk programming environments: syntax highlight and checking, version control, test framework. [Open source, GPL]
http://www.xdobry.de/xotclIDE/