#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)^#WAV\b.*(?:\R#WAV\b.*)*"
Local $sString = "#WAV 001.wav" & @CRLF & _
"#WAV "something"" & @CRLF & _
"#WAV 21021029910291029.ogg" & @CRLF & _
"....." & @CRLF & _
"#WAV 001.wav" & @CRLF & _
"#WAV "something"" & @CRLF & _
"#WAV 21021029910291029.ogg"
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