By order of impact, not chronological introduction: 0) Macro programming: I learned TCL as a kid, so that made the impact stronger; writing programs that write

By order of impact, not chronological introduction: 0) Macro programming: I learned TCL as a kid, so that made the impact stronger; writing programs that write programs is insanely powerful. Learning macro programming via TCL incidentally let me skip learning FP at the same time, which I would've with a Lisp. 1) Functional programming: correctness and beauty. Standard ML, Haskell. 2) Erlang: extreme concurrency via message passing. Erlang is functional, too. 3) C: manual memory management: Understanding how programs allocate memory. After that it gets more obscure. (Prolog, linear type systems, hardware DSLs, etc.) I feel like TCL made me numb to the Lisp bug. I might go into Clojure at some point. (Also, OOP can go suck a thumb.)