Extended Object Tcl (XOTcl): Object orientation for Tcl - shared library

 Extended Object Tcl (for short: XOTcl, pronounced exotickle) is an
 object-oriented scripting language based on Tcl. It was originally
 designed for providing language support for design patterns and
 provides novel constructs such as filters or transitive mixin
 classes. The language is designed for empowering rather than
 constraining system developers. The basic object model is highly
 influenced by CLOS.