Set a parent shell's variable from a subshell

Question

How do I set a variable in the parent shell, from a subshell?

a=3
(a=4)
echo $a

Answer 1

To change variables in a script called from a parent script, you can call the script preceded with a "."

a=3
echo $a    
. ./calledScript.sh
echo $a

in calledScript.sh

a=4

Expected output

3
4