Four German verbs in a row in a subordinate clause

I don't have many regrets in my life, but here's one. I was walking down the street in Berlin in 1992, in conversation in German with my friend Astrid (now Professor of American Studies in Tübingen). I don't remember what we were talking about, but at some point in our conversation I said something that pleased and surprised me: for the first time in German, I used a subordinate clause that ended with four verbs, in the correct order  (something like "ich habe vergessen, dass ich hätte einkaufen gehen müssen"). I regret that I don't remember what actual sentence with four consecutive verbs in a subordinate clause I said that night. (Andrew Shields, #111words, 10 May 2022)