Parsing Value with External Script

[Jean Tomaz]

I have a question.
I need to pass a value to Framed-Pool attribute only to one user, using an
external script.

My file /etc/freeradius/users

user_test Cleartext-Password := "testing"
    Auth-Type := Accept
    Framed-Protocol = PPP
    Framed-Pool = `%{exec:/bin/echo foo}`
    Fall-Through = Yes

It's not working. What it's happening?

Using the freeradius debug the Framed-Pool attribute is appearing empty.