#include <StringConstants.au3> ; to declare the Constants of StringRegExp
#include <Array.au3> ; UDF needed for _ArrayDisplay and _ArrayConcatenate
Local $sRegex = "(?m)ERRTEXT=\"(?P<ERRTEXT>.+)\",\s+MSGXML"
Local $sString = "2021-12-09 09:56:00.998, FACILITY_DETAILS="/v1/facilities/XXXX/arrears", FACILITY_ID="101010/", TIMESTAMP="2021-12-09 03:41:06.768342", CORRELATION="414d51204d425032514d30322020xxxda4b", ORIGIN="FROMORIGIIN", ERRCODE="code":"400",", ERRTEXT="detail":"must be greater than the previously recorded value of 105 days","source":{"pointer":"/data/days_past_due"}}]}", MSGXML="{"errors":[{"id":"3a59de59-8b99-4e4a-abfb-XXXXXX","status":"400","code":"400","title":"days_past_due is invalid","detail":"must be greater than the previously recorded value of 105 days","source":{"pointer":"/data/days_past_due"}}]}"" & @CRLF & _
"2021-12-09 09:56:00.998, FACILITY_DETAILS="/v1/facilities/XXXX/arrears", FACILITY_ID="101010/", TIMESTAMP="2021-12-09 03:41:06.768342", CORRELATION="414d51204d425032514d30322020xxxda4b", ORIGIN="FROMORIGIIN", ERRCODE="code":"400",", ERRTEXT="detail":"must be greater than the previously recorded value of 105 days","source":{"pointer":"/data/days_past_due"}}]}", MSGXML="{"errors":[{"id":"3a59de59-8b99-4e4a-abfb-XXXXXX","status":"400","code":"400","title":"days_past_due is invalid","detail":"must be greater than the previously recorded value of 105 days","source":{"pointer":"/data/days_past_due"}}]}""
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