need help converting this rule from 4 to 9.2.4

Wow, that's a long iRule...

Here's a start of the first part to get you going. You should be able to figure out how to convert the rest from this...

I stored some common values (host, user-agent, and uri) in local lower case variables to avoid multiple comparisons in some places just to account for case sensitivity.

when HTTP_REQUEST {
  set host [string tolower [HTTP::host]]
  set ua [string tolower [HTTP::header "User-Agent"]]
  set uri [HTTP::uri]
  if { ($host contains "demo.nature.com") || 
       ($host contains "deutsche.nature.com") ||
       ($host contains "mailart.nature.com") ||
       ($host contains "fastart.nature.com") } {
     pool nature
  } elseif { ($ua contains "google") || ($ua contains "ask") || ($ua contains "msn") } {
    pool spider_pool
  } elseif { $host contains "isn-online.org" } {
    if { ($uri equals "/") || ($uri equals "/index.html" } {
      HTTP::redirect "http://www.nature.com/isn"
    } else {
      pool Java
    }
  } elseif { $host contains "www.palgrave-journals.com" } {
    if { ($uri equals "/") || ($uri equals "/index.html" } {
      HTTP::redirect "http://www.palgrave-journals.com/pal"
    } elseif { $uri equals "/mysiteaccount" } {
      HTTP::redirect "http://www.palgrave-journals.com/nams/svc/mysiteaccount"
    } elseif { ($uri starts_with "/cgi-bin") || 
               ($uri starts_with "/services/link.taf") || 
               ($uri equals "/login/login.taf") } {
      use pool nature
    } ...
  } ...
}

Good luck and let us know if you get stuck...

-Joe