There is a growing interest in the validation of RDF based solutions where one can express the topology of an RDF graph using some schema language that can check if RDF documents comply with it. Shape Expressions have been proposed as a simple, intuitive language that can be used to describe expected graph patterns and to validate RDF graphs against those patterns. The syntax and semantics of Shape Expressions are designed to be familiar to users of regular expressions. In this paper, we propose an implementation of Shape Expressions inspired by the regular expression derivatives but adapted to RDF graphs.