The main form has an input box and a button. When the user types in some text and clicks on the button, the back-end stores in in a JSON file. (Dancer provides functions to_json and from_json. We can use Path::Tiny () and then Path::Tiny::path() with slurp_utf8 and spew_utf8 to read a file and to write it out.
When saving the item we need to save the text the user typed in and an id number. (We can use the time function of Time::HiRes. On the response page list the items we have in the file.
Next to each item add a button with the word "delete" on it. When clicking on that button, delete the item from the JSON file on the server and show the list again.