The built-in .NET Join and Split methods for strings do not provide a way for escaping the separator. If the separator is already contained in the input strings before joining, the strings cannot be reproduced by splitting: open System let inputStrings = [| "Hello, world."; "How are you?" |] let separator = ", " let joinedResult = String.Join(separator, inputStrings) let reproducedStrings = joinedResult.Split([| separator |], StringSplitOptions.None) printfn "%A" inputStrings printfn "%A" reproducedStrings[...]