Why does normal markup inside an @Using Html.BeginForm need an @?

related: https://stackoverflow.com/questions/4990717/mvc3-razor-using-html-beginform-problem

When I make an HTML form for MVC 3/VB with the Razor engine, I would expect to be able to do it like this:

@Using Html.BeginForm("Action", "Controller")
    <fieldset>
        @* Other form code and values *@
    </fieldset>
End Using

But if I do that I get "BC32035: Attribute specifier is not a complete statement. Use a line continuation to apply the attribute to the following statement." I need to add an @ character before the opening <fieldset> tag to avoid this error. Can someone explain why?

For multi-line support, as pointed out in Using in Razor VB.net MVC not work as expected, you can use @<text>...</text> to switch back to "text mode" and output html like this:

<!-- language: lang-vb -->

@Using Html.BeginForm("Action", "Controller")
    @<text>
      <fieldset>
        * Other form code and values *
      </fieldset>
    </text>
End Using