What is an iApp?

hi, I am trying to create an iRule as a part of ASO using iApp. I have some variables like pool member received from the presentation layer would like to replace in iRule. Unfortunately, after creating the iRule cannot see the original value, rather can see only the variable itself. e.g.

when RULE_INIT {

        set static::customer_pool $::pool_ip

}

I was expecting it will be like this:

when RULE_INIT {

        set static::customer_pool 10.10.1.5

}

Appreciate your earliest response on this.