返回值为什么不对呢

link-112233

exa2()
{
a=$1
b=$2
result= expr $a + $b
#echo $result
return $result
}
echo  "Enter two numbers"
read num1 num2
echo -n "result is: "
exa2 $num1 $num2
echo $?
echo "111111111111"
dd=$?
echo $dd
exa2 $num1 $num2

link-112233

exa2 $num1 $num2
echo $?
这两个的结果为什么不一样啊.

link-112233

Enter two numbers
33 44
result is: 77
0
111111111111
0
77

waker

result=$(expr $a + $b)