$ cat test.sh
some stuff
export SERVING_GW_ADDR=47.104.153.103
export TEMP_SGW_PDP_ADDR=47.104.153.103
more stuff
$ perl -pi.BAK -e '
> s/(?<=TEMP_SGW_PDP_ADDR=).*$/47.104.153.163/;' test.sh
$ head -99 test.sh*
==> test.sh <==
some stuff
export SERVING_GW_ADDR=47.104.153.103
export TEMP_SGW_PDP_ADDR=47.104.153.163
more stuff

==> test.sh.BAK <==
some stuff
export SERVING_GW_ADDR=47.104.153.103
export TEMP_SGW_PDP_ADDR=47.104.153.103
more stuff
$