iRule to Collect the HTTP Header Values into an Array.

when HTTP_REQUEST {
    set logEntry ""
    foreach headerName [HTTP::header names] {
        append logEntry "$headerName:[HTTP::header value $headerName]"
    }
    log local0 10.10.10.10 "$LogEntry
}

How about this? It doesn't actually create an array but it prints out the header names and values which seems to be what you want. You may find that the log entry is too large.

There are arrays in tcl but they are not very easy to use. You can use lists as well.