#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "[^\sGWDF](?!.?4)[0-9DTSRF]+"
Local $sString = "G4 G4 G7 G9 G9 R3 B4 RD2 R3 YD2 R4 R5 RR W BDT Y0 YS G8 WDF" & @CRLF & _
" R3 RD2 R3 YD2 R5 RR BDT Y0 YS"
Local $sSubst = ""
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