AbstractRecently, a new semantics for non-deterministic lazy functional(-logic) programming has been presented, in which the treatment of parameter passing was different to previous proposals like call-time choice (CRWL) and run-time choice (term rewriting). There, the semantics was formalized through the πCRWL calculus, and a program transformation to simulate πCRWL with term rewriting was proposed. In the present work we use the Maude system to implement that transformation and to get an interpreter for πCRWL, thus providing a first implementation of this new semantics. Besides, in order to improve the performance of the prototype, an implementation of the natural rewriting on-demand strategy has been developed, therefore taking the first steps towards obtaining a framework for on-demand evaluation of Maude system modules.