Right on, I could have sworn that I tried this exact syntax and did not see the results. Regardless, it is working now and I really appreciate the assistance. The exact syntax for the rule I have is:
elseif { [string length [HTTP::uri]] > 513 }{
log local0.longuri
redirect to http://www.mysite.com[substr [HTTP::uri] 0 513]
}
The problem we were seeing before, on v4, was that someone far away on a home DSL had the ability to slow our site by sending long URL's. F5 support thought that it might be due to the amount of iRules that we had running and the box simply had to use too many cpu cycles running these through to get to other things properly. There is probably a more elegant solution but this is the first one that I though of...
Thanks again, you all are great!