"Data is not abstracted from the language". This phrase from [About Tcl and popularity] has been echoing on my mind. I sort of understand what it means. But only so much. I can't say understand it because I still can't see the possibilities it creates. More explanation, examples and lucubrations welcomed.

----
[Category Concept]  |  [Category Example]  |  

[[Category Introspection???]]  |  [[Category Tutorial???]]  |  

[Arts and crafts of Tcl-Tk programming] - is that a category?