Why use HTML_QuickForm_advmultiselect ?

I am sure we have all been there, dealing with HTML_QuickForm because we need to allow users to select multiple options. With a standard html select box, you can select multiple options if the multiple attribute is set, but you have to hold down the appropriate modifier key (ctrl on windows) in order to do so. It is not a problem for end-user experts, but it is not true for all of us.

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