Variable Scope & Lifetime

I am relatively new to iRule development and I need a little help understanding variable scope. My main objective is to understand how I pass values from the HTTP_REQUEST event to the HTTP_RESPONSE event for a single HTTP handshake. Here is an example:

 

 

when HTTP_REQUEST {

 

if {[TCP::local_port] == 80} {

 

set protocol "http"

 

} else {

 

set protocol "https"

 

}

 

set url "$protocol://[HTTP::host][HTTP::uri]"

 

}

 

 

when HTTP_RESPONSE {

 

HTTP::respond 200 content "$url"

 

}

 

 

Here are some questions I have:

 

 

1. Will the above iRule always return the client's original request URL?

 

2. What is the scope and lifetime of a local variable?

 

3. What is the scope and lifetime of a global variable?

 

4. Should I use the global command to declare globals instead of set ::varname? There is significant tcl documentation that implies that this performs better.

 

5. Is there any documentation on this?

 

 

Thanks