Common Lisp was already suggested by I'm going to elaborate.
I was actually very disappointed when I didn't find a single language with simple syntax like Tcl, Common Lisp or Scheme (or Racket) while there are quite a few even less known languages like Dart, Groovy or OCaml. I'm going to make my pick and vote for Common Lisp.
Listing just the features missing in other languges you have:
1. Nice and simple prefix syntax.
2. Nice and simple syntax macros. I'm aware a few other languages like Scala have them too but they all look like kludges due to complex infix syntax.
3. Strong but dynamic type system. Yes, it shares it with E.g. Ruby and Python and it's (IMO) the best trade-off between safety and ease of use unless you can infer all types statically like Haskell does.
4. Both lexically-scoped and dynamically-scoped variables. No other language you support (I think) even has dynamiclly-scoped variables.
5. Runtime interactive debugger... not sure if you can make it work or not but...
6. The signal-restart error handling system will work regardless even if you can't support interactive features.
So pick a supported implementation like CCL, SBCL or CLisp. I'd be glad to help you out.
Also @Jabberwockey SBCL is not a dialect of CL. CL has no dialects. SBCL is an implementation of CL.
EDIT: After solving a few puzzles three more points.
1. CL is one of the few multiparadigm languages with Metaprogramming, FP, Structured programming and OOP all supported on a pretty good level and easy to mix. Not as good as specialised languages but still. Also its OOP system CLOS has enough unique ideas behind it.
2. All puzzles I saw yet have a main loop and CL's LOOP macro is good for this.
3. Miss COND too.