Liquid to add tags to new customer on creation + create a new tag with the company name field prefixed with 'company_'

Tags in reg form.liquid

<div id="company_name_field" class="clearfix large_form">
      <label for="company_name" class="login">
           Trading / Store Name - to appear on invoices and our store locator *
      </label>
      <input type="text" value="" name="customer[note][Company Name]" id="company_name" class="large" size="30" required />
</div>        

<input type="hidden" id="processed_prospect_and_company_name" name="customer[tags]" value="Prospect"/>

<script type="text/javascript">
    $(document).on('ready', function() {
        $('#company_name').on('blur', function() {
            var companyName = $('#company_name').val().replace(/[.,\/#!$%'\^&\*;:{}=\-_`~()]/g,"");
            $('#processed_prospect_and_company_name').val('Prospect, company_' + companyName);
    });
</script>