The primary executable that comes with Tcl is `tclsh`. Not really sure what `tclish` is, as I initially thought it was a typo. However, there seems to be references to it based on a quick search (e.g. [here](https://wiki.tcl-lang.org/page/Tclish) and [here](https://tclish.sourceforge.net/)), so maybe it's a valid executable that I just haven't been aware of. I was hesitant to replace it and instead opted to just add `tclsh`.