iRule for Response Header "content-length"

"err tmm1[17512]: 01220001:3: TCL error: /Common/xml_rule - Illegal argument (line 2) invoked from within "HTTP::collect [HTTP::header Content-Length]" " error message in /var/log/ltm when no any soap data was sent.

does content-length header exist (i.e. [HTTP::header content-length] is not null)?

what about something like this?

when HTTP_REQUEST { 
  if { [HTTP::header exists Content-Length] } {
    HTTP::collect [HTTP::header Content-Length] 
  } else {
     do something
  }
} 
when HTTP_REQUEST_DATA { 
  if { [findstr [HTTP::payload] "list" 1 " x" ] contains "test_string" } {
    pool test1 
  } else {
    pool test2
  }
}