#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(?<=\<a.*?www\.)([a-z]+\.[a-z]+)"
Local $sString = "<a href="https://www.domainurl.com/refer/google-adsense/">fsdf</a>" & @CRLF & _
"<a title="Google Adsense" href="https://www.domainurl.com/refer/google-adsense/" target="_blank" rel="nofollow noopener">fgddf</a>" & @CRLF & _
"<a href="https://www.domainurl.com/page/pago">domain </a>"
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