[[so is someone going to write up some description of Tcl's 
stacked channel support?]]

The [C] API is documented in http://www.tcl.tk/man/tcl8.4/TclLib/ChnlStack.htm.
Extensions [Trf] and [TLS] rely heavily on the stacked channel mechanisms.

Also called channel [transform], [virtual channel], and [reflected channel] - so some agreed-upon nomenclature would be good.

----
[[
[Category Channel] |
[Category Concept]
]]