This paper presents the toolkit snakes that is aimed at providing a flexible solution to the problem of quickly prototyping Petri nets tools. In particular, snakes is expected to have as few built-in limitations as possible with respect to the particular variant of Petri net to be used. The goal is to make snakes suitable for any kind of Petri net model, including new ones for which there exists no available tool. For this purpose, snakes is designed as a very general Petri net core library enriched with a set of extension modules to provide specialised features. On the one hand, the core library is versatile in that it defines a general Petri net structure where all the computational aspects are delegated to an interpreted programming language. On the other hand, extension modules provide with enough flexibility to allow to redefine easily any part of the base Petri net model. In particular, snakes comes with a handful of extension modules in order to handle models of the Petri Box Calculus and M-nets family. snakes is released under the gnu lgpl, it can be downloaded, together with api documentation and a tutorial, at http://lacl.univ-paris12.fr/pommereau/soft/snakes.