iRule to read key/value pair from Data Group lists

I always like to check that the value of a header or cookie is not null instead of checking to see if it exists before trying to use the value. It's an odd corner case to check for, but I've seen a few rules break by assuming the header or cookie will have a value if it's present.

  if {[HTTP::header "myCustomHeader"] ne ""} {
    ...

If the header isn't set, the header command will return a null string. You don't have to worry about an error if the header doesn't exist.

Aaron