I used expect once some years ago, but changed to using ruby's #expect method[1]. I think the reason I changed was because, in TCL, some functions seem to keep track of stuff by setting variables in the caller's scope. So, if I took some code I wrote and defined a new function with it, substituting the code with a call to the new function, stuff would break because calls to predefined expect functions wouldn't have the same caller's scope anymore.

I wish I had a concrete example to share so someone here could confirm, but like I said, it was some years ago.

[1] https://ruby-doc.org/stdlib-2.6.4/libdoc/pty/rdoc/IO.html#M0...