#!/bin/ksh -p

name="this.is.a.test.ac.uk"
name2=$(echo $name|sed 's/\./ /g')

set -A k $name2
length=${#k}

out=""
i=$((length+1))
while ((i > 0)) ; do
  out=$out${k[$i]}"."
  i=$((i-1))
done

out=$out${k[0]}

echo $out