Complex applications was probably an overstatement but I've created featureful IRC and Discord bots, a database management application and right now I'm creating a graphical browser for the Gemini protocol.

All my other previous attempts at using functional languages, like for instance Haskell, ended up in trivial applications, usually based in numerical analysis.

My latest project was: Get some emails using IMAP, login to my site, find and scrap some data related to the sender of the email, and send a reply using SMTP. The logic is not very complicated, it uses 4 or 5 of the standard libraries and I avoid writing a hundred emails per day.