Variable pointers
Indirection Operator
~$ foo=bar
~$ bar=42
~$ echo ${!foo}
42
Dynamic Variable Name Assignment
~$ foo=bar
~$ read -r ${foo} <<< "42"
~$ echo $bar
42
~$ foo=bar
~$ bar=42
~$ echo ${!foo}
42
~$ foo=bar
~$ read -r ${foo} <<< "42"
~$ echo $bar
42