nixpkgs/pkgs/development/tcl-modules/by-name/README.md

Name-based Tcl package directories

The structure of this directory is identical to the one described in /pkgs/by-name/README.md. The only difference is the scope:

{
  lib,
  # You can get tclPackages attributes directly
  mkTclDerivation,
  tcllib,
}:

mkTclDerivation {
  # ...
}