Proc for fully decoding URI's

Thanks for clarifying this and confirming that HTTP:: TCP::, etc commands are offlimits in proc's even if the HTTP_REQUEST event or CLIENT_ACCEPT is calling the proc

I would just add that this shouldn't be a problem. You generally need a protocol-level event to trigger iRule processing, so whatever data is accessible in that event can be sent to the proc as a parameter. A dirty example:

proc doSomethingWithUri { uri } {
    set foo [URI::decode $uri]
    return $foo
}
when HTTP_REQUEST {
    if { [string tolower [HTTP::uri]] starts_with "/app1" } {
        set ret [call doSomethingWithUri [HTTP::uri]]
        log local0. $ret
    }
}