How to connect a form submission to a mailchimp tag within an audience

When I setup a form on my site, I need the submissions to go into my general audience within mailchimp, but also be tagged referencing that specific form. I will not setup a difference audience for each form, as it gets messy and confusing. I see that I can direct submissions to go to the general audience, but it does not allow me to automatically tag that submission to reference that form. (IE. a lead magnet)

Does anyone have a suggestion for a way to make this happen without using another integration software like zapier?

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