This iRule should be simple

The pool command affects the destination for the current TCP connection. Subsequent HTTP requests within the same connection will go to the selected pool unless you specifically tell it to go elsewhere. Looking over your iRule I can't see any large optimizations but here are some updates that may assist.

 Send traffic to a secure service when string found in URI
when HTTP_REQUEST { 
  set secure_service 0 
  if { [HTTP::uri] contains "/abc/s" } { 
    HTTP::uri "/10521/[findstr [HTTP::uri] {abc} 4]"
    snatpool secure_snat 
    pool secure 
    set secure_service 1 
    log "The secure request received is [findstr [HTTP::uri] {abc} 4]" 
    log "The secure URL is [HTTP::uri]" 
  } else { 
    pool my.site.com
    SSL::disable 
    log "Client connected to default pool - [LB::server] " 
    log "The securentry URL is [HTTP::uri]" 
  } 
} 
when HTTP_RESPONSE { 
  if { $secure_service } { 
    log "HTTP Status is [HTTP::status] from server [IP::remote_addr]" 
    log "Service is $secure_service" 
  } 
}

- results of commands inside an event are cached so you can use repeatedly

- zero is false, 1 is true

- the first "if" defines what is considered a secure service, the second "if" is redundant as a result.

- SSL::disable can be used in the HTTP event.

Jarvil