Can I have a iRule do 2 actions when it matches a uri?

Well, there's two things going on here.

1. First, you cannot send to a pool and redirect at the same time. It's conflicting logic.

2. You're causing a loop because your redirect always matches the first condition. If URI starts with /app1, redirect to /app1/app/login.aspx...and repeat indefinitely. Your best bet may be to be more specific with your condition. Something like this:

   when HTTP_REQUEST {
       if { [string tolower [HTTP::uri]] equals "/app1" } {
           HTTP::redirect "http://[HTTP::host]/app1/app/login.aspx"
       } elseif { [HTTP::uri] equals "/app1/app/login.aspx" } {
           pool app1
       } else {
           pool everythingelse
       }
   }
   

Or perhaps this:

when HTTP_REQUEST {
    if { [string tolower [HTTP::uri]] equals "/app1" } {
        HTTP::redirect "http://[HTTP::host]/app1/app/login.aspx"
    } elseif { [HTTP::uri] starts_with "/app1/" } {
        pool app1
    } else {
        pool everythingelse
    }
}