Reading User-Agent field for spiders

Ok, wondered what the underscore was for in the article I referenced earlier. Rules is not working right now, receiving Page Reset error. I've looked through some posts and saw that putting log local0 will put the output of the rule into the ltm log. How would that best be implemented in this rule?

 

 

when HTTP_REQUEST {

 

log local0. if { [matchclass [HTTP::header User-Agent] contains "Googlebot"] } {

 

pool nsa_[HTTP::header Host]

 

}

 

else {

 

pool www-l3_[HTTP::header Host]

 

}

 

}

 

 

Thanks for any assistance.