<block>
 <name>Bob</name>
 <address>USA</address>
 <email>$BOB_EMAIL</email>
 <phone>1234567</phone>
</block>

<block>
 <name>Peter</name>
 <address>France</address>
 <cell>123123123</cell>
 <drinks>Coke</drinks>
 <car>$PETER_CAR</car>
 <bike>Mountain bike</bike>
</block>

JOE_EMAIL=joe@google.com
BOB_EMAIL=bob@hotshot.com
JACK_EMAIL=jack@jill.com
MARY_EMAIL=mary@rose.com
PETER_EMAIL=qwert1@abc.com

JOE_CAR=Honda
DAISY_CAR=Toyota
PETER_CAR=Mazda
TOM_CAR=Audi
BOB_CAR=Ferrari

NAME="Bob"
sed -n '/name>'${NAME}'/,/</block>/s/.*<(.*)>(.*)<.*/1=2/p' sample.xml

name=Bob
address=USA
email=$BOB_EMAIL
phone=1234567

Name=Peter

name=Peter
address=France
cell=123123123
drinks=Coke
car=$PETER_CAR
bike=Mountain bike

name=Bob
address=USA
email=bob@hotshot.com
phone=1234567

name=Peter
address=France
cell=123123123
drinks=Coke
car=Mazda
bike=Mountain bike