Problem about execute external program

[Kun Niu]

Dear all,

I'm trying to use an external script written by myself.
And I insert the following line into my mysql database.
INSERT INTO radreply( UserName,Attribute, Value ) VALUES( "123",
"Session-Timeout", "%{exec:/path/to/myprogram}" );
And I insert exec into instanciate and authorize section.
But the server failed to send the session-timeout to my client.

the following is "myprogram"

#!/usr/bin/perl -w

print "Session-Timeout==1800";

And my exec section is like this:
exec {
wait = yes
inputpairs=request
outputpairs=response
program="/path/to/myprogram"
packet_type=Access-Accept
}

Have I missed anything?
Any help would be appreciated and thanks in advance.

Sincerely,
Kun