A description of the design and implementation of a language platform called April++ and its use on a number of applications. Methodologically, in designing and implementing the language, a layered approach has been adopted. April++ has been developed as a series of macro defined layers on top of the relatively primitive features of a pre-existing language called April. On top of April++, an agent layer has been built (as a set of predefined classes) for constructing agent-based systems. This layer has been customised for specific application domains considered. This includes a mobile agent application, a distributed database application and a network management one.