@function select-buttons($buttons: '*')
{
    @return select-either(
        select-as-children(select-class(buttons) li $buttons),
        select((a label) select-class(button) $buttons),
        select(button $buttons),
        select('input[type=submit]' $buttons)
    );
}

@mixin select-buttons($buttons: '*')
{
    #{ select-buttons($buttons) } { @content; }
}