‘gis’ I believe is a term used by programmers.
but for what you are looking for you do not need to worry about this
have you looked at the form that I sent you over ? the script under the validate button shows how you can check a field to ensure that the 2 components (@ and .) are present before it will allow the user to continue.
I trust you haven’t set up your script to search for ‘.’ so it shows in the behaviour window as “‘.'” ? compare what you have tried to the script in the example form I sent to check this isn’t the case