The paper presents a method for describing the operational semantics of programming languages. It is based on a domain-specific language designed to specify executable specifications for programming language constructs. This language is an extension of the Lisp language. The peculiarity of the method is to set the semantics for the program model, and not for the program itself. Since the specifications are executable, the method actually allows to ‘program‘ the semantics of programming languages. The method can be used in teaching computer languages, as well as in creating new programming languages, since it allows you to describe the constructions of a new language immediately at the level of an abstract syntactic tree.