You can also write it in a more XSLT-2-ish way,

let $sequence := ("Simon", "David", "Joy", "Nigel", "Nicola")
return map:merge(
   for $i in 1 to count($sequence)
   return map:entry($sequence[$i], $i)
)

(for $v at $p in ('amount', 'vat-rate', 'total') return map:entry($v,
$p)) => map:merge()