I have a script foo.sh

```
 CMD='export FOO="BAR"'
 $CMD
 echo $FOO

```

It works as expected

```
 >./foo.sh 
 "BAR"

```

Now I want to change FOO variable to `BAR BAR`. So I get script 

```
 CMD='export FOO="BAR BAR"'
 $CMD
 echo $FOO

```

When I run it I expect to get `"BAR BAR"`, but I get 

```
 ./foo.sh: line 2: export: `BAR"': not a valid identifier
 "BAR 

```

How I can deal with that?