Several important data structures in programming are beyond trees. For example, difference lists, doubly-linked lists, skip lists, threaded trees, and leaf-linked trees. They can be abstracted into graphs (or, more precisely, port hypergraphs). In existing imperative programming languages, these structures are handled with destructive assignments to heaps, as opposed to a purely functional programming style. These low-level operations are tiresome, prone to errors, and difficult to verify. On the other hand, purely functional languages allow handling data structures declaratively with type safety. However, existing purely functional languages are incapable of dealing with data structures other than trees succinctly. In earlier work, we proposed a new statically typed purely functional language, λGT, that handles graphs as immutable, first-class data structures with pattern matching This paper presents a prototype implementation of the language constructed in only 500 lines of OCaml code. We believe this is usable for further investigation, including in the design of full-fledged languages based on λGT.