Racket

Racket's interactive mode encourages experimentation, and quick scripts easily compose into larger systems.

Small scripts and large systems both benefit from native-code JIT compilation. When a system gets too big to keep in your head, you can add static types.

Extend Racket whenever you need to. Mold it to better suit your tasks without sacrificing interoperability with existing libraries and without having to modify the tool chain. When less is more, you can remove parts of a language or start over and build a new one.