Abstract. The functional programming community has developed a number of powerful abstractions for dealing with diverse programming models in a modular way. Beginning with a core of pure, side effect free computation, modular monadic semantics (MMS) allows designers to construct domain-specific languages by adding layers of semantic features, such as mutable state and I/O, in an à la carte fashion. In the realm of interpreter and compiler construction, the benefits of this approach are manifold and well explored. This paper advocates bringing the tools of MMS to bear on hardware design and verification. In particular, we shall discuss a prototype compiler called ReWire which translates high-level MMS hardware specifications into working circuits on FPGAs. This enables designers to tackle the complexity of hardware design in a modular way, without compromising efficiency.