#include <StringConstants.au3> ; to declare the Constants of StringRegExp
#include <Array.au3> ; UDF needed for _ArrayDisplay and _ArrayConcatenate
Local $sRegex = "(?m) (SessionID=".*?")?(?: .*(MsgType=".*?"))? "
Local $sString = "2021-10-07 10:32:05,767 ERROR [LAWT2] blah.blah.blah - Message processing FAILED: <ExecutionReport blah="xxx" foo="yyy" SessionID="kkk" MoreStuff="zz"> Total time for which application threads were stopped: 0.0003858 seconds, Stopping threads took: 0.0000653 seconds" & @CRLF & _
"2021-10-07 10:31:32,902 ERROR [LAWT6] blah.blah.blah - Message processing FAILED: <NewOrderSingle SessionID="zkx" TargetSubID="ttt" Account="blah" MsgType="D" BookingTypeOverride="0" Symbol="6316" OtherField1="othervalue1" Otherfield2="othervalue2"/></D></NewOrderSingle>"
Local $aArray = StringRegExp($sString, $sRegex, $STR_REGEXPARRAYGLOBALFULLMATCH)
Local $aFullArray[0]
For $i = 0 To UBound($aArray) -1
_ArrayConcatenate($aFullArray, $aArray[$i])
Next
$aArray = $aFullArray
; Present the entire match result
_ArrayDisplay($aArray, "Result")
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm