#!/bin/bash
s="nie[breath]hi
hi </langenglish>'tjie"
sed 's/[[:space:]]*\([]>]\)[[:space:]]*/\1 /g;s/[[:space:]]*\([[<]\)[[:space:]]*/ \1/g' <<< "$s"
IyEvYmluL2Jhc2gKcz0ibmllW2JyZWF0aF1oaQpoaSA8L2xhbmdlbmdsaXNoPid0amllIgpzZWQgJ3MvW1s6c3BhY2U6XV0qXChbXT5dXClbWzpzcGFjZTpdXSovXDEgL2c7cy9bWzpzcGFjZTpdXSpcKFtbPF1cKVtbOnNwYWNlOl1dKi8gXDEvZycgPDw8ICIkcyI=