#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)#(?=item)"
Local $sString = "#333 /*do not track*/" & @CRLF & _
"#ff0000 /*do not track*/" & @CRLF & _
"#item1 /*found*/" & @CRLF & _
"#item2 /*found*/" & @CRLF & _
"#item3 /*found*/" & @CRLF & _
"#item /*found*/" & @CRLF & _
"#item /*found*/" & @CRLF & _
"#item /*found*/"
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