I wasn’t actually maintaining software across this divide, but I do still occasionally see Tcl 7.x installations in the wild and find it quite recognizable. It seemed to me the biggest changes from 7->8 were byte code interpreter and “dual ported” Tcl_Obj to store values vs naive C strings(which should have only exposed themselves as “improved performance”).

The release notes[0] for Tcl 8 seem to list minor-ish annoyances, but perhaps you did have to support something across the 7-8 divide; I won’t argue against your experience in that case.

> As always, the best way to predict the future is to make it

Truth.

[0] https://www.tcl.tk/software/tcltk/8.0.html#incompatibilities