Search word in body content

Dear,

I run into the problem of making a irule you find a word in the body of the page that loads and take an action.

Try something like this but does not work

September static :: errocuerpo "invalid"

} Elseif {[findstr [HTTP :: payload] $ static :: errocuerpo] == "invalid"} { log local0. "login fail" }

The method without static group are?

thanks