You may be interested to look at the TIP #280 code that added enhanced stack frame...
Clear undo stack after loading text into editor
Change Built-in Diffie-Hellman key from 512 to 2048 bits
Expect 5.40 for windows, source code required
You can find the sources at: ftp://ftp.tcl.tk/pub/incoming/expect-src.zip
Definitely in favor of committing to core tls with version bump.