The L Programming Language & SystemL is both a language and an operating environment, like Smalltalk. It is capability-secure and distributed, like E. The language is a derivative of lambda calculus, hence it is small, block-structured, dynamically-typed, and functional. State is implicitly threaded through all function calls and returns, allowing simulation of dynamic scope and side-effects. Each thread runs in its own transaction, upon completion its state changes are committed. Any concurrent threads that conflict are aborted and re-executed at a higher priority. Each commited state change is an event. Event handlers spawn new threads (repeating the cycle).