Cannot get HTTP::header at to work

All -

 

 

I can't get [HTTP::header at] to work at all.

 

 

I searched for examples of [HTTP::header at] on the forum; I found a couple of examples, both of which are more sophisticated than what I need.

 

 

I have the following in my iRule:

 

 

set i 0

 

set thisHeader ""

 

set totalHeaders [ HTTP::header count ]

 

while { $i < $totalHeaders }

 

{

 

set thisHeader [HTTP::header at $i ]

 

incr $i

 

}

 

 

Now, ignore the pointlessness of the code for now - it's just to test with. I'm getting this error:

 

 

TCL error: My_iRule - Illegal argument. Illegal argument. Illegal argument. Illegal argument. Ille (line 1) invoked from within "HTTP::header at $i "

 

 

I've even tried this:

 

 

set myHeader [HTTP::header at 0]

 

 

Error reported:

 

TCL error: My_iRule - Illegal argument. Illegal argument. Illegal argument. Illegal argument. Ille (line 1) invoked from within "HTTP::header at 0"

 

 

Am i doing something stupidly wrong? I'm on BIG-IP 10.0.1 Build 283.0 Final.

 

 

thanks for any help!