#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?Jsm)^((?|[1-9](?=.*1\t+(?<x>0+))|[1-9]\d(?=.*2\t+(?<x>0+))|[1-9]\d{2}(?=.*3\t+(?<x>0+))|[1-9]\d{3}(?=.*4\t+(?<x>0+))|[1-9]\d{4}(?=.*5\t+(?<x>0+))|[1-9]\d{5}(?=.*6\t+(?<x>0+))|[1-9]\d{6}(?=.*7\t+(?<x>0+))|[1-9]\d{7}(?=.*8\t+(?<x>0+))))\b"
Local $sString = "1" & @CRLF & _
"12" & @CRLF & _
"123" & @CRLF & _
"12345678" & @CRLF & _
"123456789" & @CRLF & _
"" & @CRLF & _
"1 00000000" & @CRLF & _
"2 0000000" & @CRLF & _
"3 000000" & @CRLF & _
"4 00000" & @CRLF & _
"5 0000" & @CRLF & _
"6 000" & @CRLF & _
"7 00" & @CRLF & _
"8 0"
Local $sSubst = "${x}$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