#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(\d+)(?=(,|:).*?~.*?~.*?\1_(.))|#|,|:.*"
Local $sString = "#1,0110,0010:~;0101_1000;0110_1001;0111_1010;1000_1011;1001_1100;1010_1101;1011_1110;1100_1111,~0000_00001_10010_20011_30100_40101_50110_60111_71000_81001_9"
Local $sSubst = "$3"
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