Covering a few days later than I thought I would, but what else do I see in Expect's codebase?
* Deprecated `select`-syscall I/O utilities, disabled in all builds
* API around terminal-windowsize accessing IOCTLs
* It's own date-formatting utility
* Opening sub-pseudoteletypes
* Implementation of glob-patterns
* Utilities upon those sub-pseudoteletypes, across 2 files
* Multiple sources for input events, including a noop one
* Configuring redirects on /dev/console
* Legacy cleanup routine
1/2?