NaTcl is Tcl running under Chrome.
Edit tcl.nmf to
{ "nexes": { "x86-32": "exe/tcl.nexe", } }
Add to site.config:
/natcl/ { domain File root $Wub::docroot/NaTcl } /natcl/exe { domain File root $Wub::docroot/NaTcl/exe expires tomorrow }