Request for decoding iRules

Hello,

Can someone provide me with a quick breakdown of what the following iRule commands are doing? Thank you!

when CLIENT_ACCEPTED {
   # Open High Speed Logging handle to syslog_pool 
   set hsl [HSL::open -proto UDP -pool pool_syslog] 
   log local0. "Connection from [IP::client_addr]"

} 
when HTTP_REQUEST {
   # Iterate through each header in the request and send a log msg 
   foreach headr [HTTP::header names] { 
      HSL::send $hsl "$headr [HTTP::header $headr]" 
   } 
   # Collect the Content-Length of the body and trigger HTTP_REQUEST_DATA 
   HTTP::collect [HTTP::header "Content-Length"]
}
when HTTP_REQUEST_DATA { 
   # Set the payload we captured in HTTP_REQUEST to $RequestData 
   set RequestData [HTTP::payload] 
   log local0. $RequestData 
   # if there is a pSessionId, let\'s find it Switch Statement Here!!! 
   if {$RequestData contains "pSessionId"} {
      set pass1 [getfield $RequestData "pSessionId>" 2] 
      log local0. "pass1 is $pass1" 
      # switch statement to handle variants of sessionIds coming from AS400
      switch -glob $pass1 { 
         "ROS-" { 
            set ROSpass [getfield $pass1 "<" 1] 
            log local0. "ROSpass is $ROSpass" 
            set pSessionId $ROSpass 
         }
         "" { 
            log local0. "Checking for pass1 again: $pass1" 
            set CDATApass [getfield $pass1 "CDATA[" 2] 
            log local0. "CDATApass is $CDATApass" 
            set CDATApass2 [getfield $CDATApass "]" 1] 
            log local0. "CDATAPass2 is $CDATApass2" 
            set pSessionId $CDATApass2 
         }
      } 
      log local0. "pSessionId is $pSessionId"
      # persist on pSessionId for 3mins 
      persist uie $pSessionId 180 
   } else { 
      log local0. "No pSessionId" 
      set NOpSessionId 1 
   }
   # Log the body of the request 
   HSL::send $hsl $RequestData
} 
when HTTP_RESPONSE {
   # Iterate and log response headers 
   foreach headr [HTTP::header names] { 
      HSL::send $hsl "$headr [HTTP::header $headr]"
   } 
   # Collect the response body and trigger HTTP_RESPONSE_DATA
   HTTP::collect [HTTP::header "Content-Length"] 
}
when HTTP_RESPONSE_DATA { 
   # Set the payload we captured to $ResponseData 
   set ResponseData [HTTP::payload] 
   log local0. $ResponseData
   # If there wasn't a pSessionId on the request look for it now...
   if {[info exists NOpSessionId]} { 
      # Code to handle session creation by Route Objects server 
      if {$ResponseData contains "LogonResult>"}{ 
         set respasstemp [getfield $ResponseData "LogonResult>" 2] 
         set pSessionId [getfield $respasstemp "<" 1] 
         log local0. "This is the logonresult from responsedata: $pSessionId"
      } else { 
         if {$ResponseData contains "pSessionId"} { 
            set respass1 [getfield $ResponseData "pSessionId>" 2] 
            log local0. "respass1 is $respass1" 
            # switch statement to handle variants of sessionIds on all subsquent responses 
            switch -glob $respass1 { 
               "ROS-*" { 
                  set resROSpass [getfield $respass1 "<" 1] 
                  log local0. "resROSpass is $resROSpass" 
                  set pSessionId $resROSpass
               } "