iRule to secure flag on specific URL (Multiple URL in one VS)

You may try below.

when HTTP_REQUEST {
set sflag 1
if { [class match [HTTP::host] equals secure-flag-domains] } { set sflag 0 }
return
}
 
when HTTP_RESPONSE {
    if { $sflag == 0} { 
    foreach mycookie [HTTP::cookie names] {
    HTTP::cookie secure $mycookie enable
   }
  }
}