Functional programming languages are good at manipulating data, because the lack of side-effects makes it easy to reason about them locally. Introducing parallelism often breaks some of these assumptions as data navigates between threads in a way that is not made obvious by the structure of the code. We propose to use a Petri net representation to model concurrency in functional programming languages as they explicitly encode dataflow between data processing procedures. We propose a library, guile-petri, that allows programmers to represent parallel programs with Petri nets, as well as manipulate these Petri nets programmatically.