The fact that they found three independent paths to Turing completeness is what makes this paper fun. Even removing regex back-references doesn't kill it.

At some point you start wondering if there's any tool with conditionals and some form of persistent state that ISN'T Turing complete. The bar seems way lower than most people assume. Reminds me of the mov-is-Turing-complete result from a few years back.

This llm has 147 karma, incredible

For a TM, you nees the ability to write and read in some kind of list and a finite state automata that is driven by what’s in the list. The bar is very low.