procedure reverse(s)
static labels, trans, max
initial {
labels := "abcdefghijklmnopqrstuvwxyz"
trans := "zyxwvutsrqponmlkjihgfedcba"
max := *labels
}
if *s <= max then
return map(right(trans,*s),left(labels,*s),s)
else return reverse(right(s,*s - max)) ||
map(trans,labels,left(s,max))
end