#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(?:ONE.*)?(ONE.*)"
Local $sString = "1 ONE;TWO;THREE;ONE;FOUR;FIVE" & @CRLF & _
"2 ONE;TWO;THREE" & @CRLF & _
"3 TEST" & @CRLF & _
"4 TEST" & @CRLF & _
"5 TEST"
Local $sSubst = "\1"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
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