#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)<img[^>]+data-src=("[^"]+")[^>]*>"
Local $sString = "<img src="old.jpg" data-src="new.jpg">" & @CRLF & _
"<img data-src="new2.jpg" src="old2.jpg">"
Local $sSubst = "<img src=$1 data-src=$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