multiple iRules

I would disagree with Vijay_E, in my option, using multiple, more concise iRules and using priority to control the order they are triggered is a much better option.

smaller iRules are easier to manage, priority gives the control over what happens in what order

# iRule 1
when HTTP_REQUEST priority 10 {
    # triggered first
}
 
# iRule 2
when HTTP_REQUEST priority 20 {
    # triggered second 
}
 
 

https://clouddocs.f5.com/api/irules/priority.html