Hi Adam,
let $vbFailure1 := ($perm?authorization != 'example' or exists( $perm?authorization )=false())
If you want, you can simplify this to:
let $vbFailure1 := not($perm?authorization = 'example')
If $perm?authorization yields no item (i.e., an “empty sequence”), the comparison () != 'example' will give you false, because there is no item on the left-hand side of the comparison that matches 'example'.
Hope this helps, Christian