Outline
 
 
An example:
- Tcl: universal scripting language.
 - Tk: GUI toolkit based on Tcl.
 
Language rationale:
- Unusual design goals (e.g. extensibility).
 - Key features:
- Unstructured (everything's a string).
 - No grammar.
 - Quote by default.
 - Substitutions.
 
 
Challenge: raise the level of language design.