In my oh-so-abundant free time, I've been working on my own little text editor. And one of my motivations is TECO: one of the oldest, and one of the very best, ever written. It's both a text editor and a programming language - and, in fact, that's exactly what made it such a brilliant tool. So much of the drudgery of programming is stuff that really could be done by a program. But we've spent so much time learning to be fancy that we've lost track of that. Nowadays, you can write an emacs lisp program to do the stuff you used to do in TECO; only it's awkward enough that you usually don't.
The problem, though, with just re-implementing TECO with a modern UI is that it was designed in a different time. When TECO was written, every byte was critical. And so the language, the syntax, the structure, it was completely ridiculous. And, as a result, it became the world's most useful pathological programming language. It's a glorious, hideous, wonderful, horrific piece of computing history
TECO is one of the most influential pieces of software ever written. If, by chance, you've ever heard of a little editor called "emacs"; well, that was originally a set of editor macros for TECO (EMACS = Editor MACroS). As a language, it's both wonderful and awful. On the good side, The central concept of the language is wonderful: it's a powerful language for processing text, which works by basically repeatedly finding text that matches some kind of pattern, taking some kind of action when it finds it, and then selecting the next pattern to look for. That's a very natural, easy to understand way of writing programs to do text processing. On the bad side, it's got the most god-awful hideous syntax ever imagined.