#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "RT(\A|\s)@(\w)+"
Local $sString = "RT @iamkhiofficial2323: #lahore #LahoreBlasts : #punjabgovt 9 #dead. 20 #injured. https://t.co/UU7doEtTmZ #pray #unite #notgivingup RT @iamkhiofficial2323" & @CRLF & _
" RT @iamkhiofficial2323"
Local $sSubst = "<label class="">$0</label>"
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