#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)<tag>.*?\K(?!<!CDATA\[[^\n\]]*\]>(?:[^>]|$))((?:<!|!<)CDATA\[.*?\]+>+)(?=.*<\/tag>)"
Local $sString = "<tag>data...<!CDATA[...]]>...otherdata..!<CDATA[....]>>....</tag>" & @CRLF & _
"" & @CRLF & _
"<tag>data......otherdata..!<CDATA[....]>>....</tag>" & @CRLF & _
"" & @CRLF & _
"<tag>data...!<CDATA[|]]>...otherdata......</tag>" & @CRLF & _
"" & @CRLF & _
"<tag>data...<!CDATA[asdfghjkl]>...otherdata......</tag>" & @CRLF & _
"" & @CRLF & _
"" & @CRLF & _
"" & @CRLF & _
"" & @CRLF & _
"<tag>data...<!CDATA[...]]>...otherdata..!<CDATA[....]>>...." & @CRLF & _
"" & @CRLF & _
"data...<!CDATA[...]]>...otherdata..!<CDATA[....]>>....</tag>" & @CRLF & _
"" & @CRLF & _
"<tag2>data...<!CDATA[...]]>...otherdata..!<CDATA[....]>>....</tag2>"
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