#include <StringConstants.au3> ; to declare the Constants of StringRegExp
#include <Array.au3> ; UDF needed for _ArrayDisplay and _ArrayConcatenate
Local $sRegex = "(?i)<tag_([A-Z0-9]*)\b[^>]*>.*?<tag_([A-Z0-9]*)\b[^>]*>[^\/]*?(?!(\/tag_\2))\/tag_\1>"
Local $sString = "<tag_1> xx <tag_2> xx </tag_1> xx </tag_2> xx <tag_1> xx <tag_3> xx <tag_4> xx </tag_4> xx </tag_3> </tag_1>"
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