I have previously used graph-easy[1] to turn Graphviz/DOT files into ASCII for code comments. It is great for state machines or explaining the relationship between different systems or classes, and if you check in the DOT file alongside the code, it is not too difficult to update later if something changes.

[1] https://metacpan.org/release/TELS/Graph-Easy-0.64/view/bin/g...

This is pure genius! Interactiy building ASCII diagrams!! Well executed