#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(\w*)\s(\w*)\n([^}])"
Local $sString = "HEADER1:{" & @CRLF & _
"key value" & @CRLF & _
"key value" & @CRLF & _
"..." & @CRLF & _
"HEADER2:{" & @CRLF & _
"key value" & @CRLF & _
"..." & @CRLF & _
"},key value" & @CRLF & _
"HEADER3:{" & @CRLF & _
"key value" & @CRLF & _
"HEADER4:{" & @CRLF & _
"key value" & @CRLF & _
"..." & @CRLF & _
"}" & @CRLF & _
"},key value" & @CRLF & _
"}" & @CRLF & _
""
Local $sSubst = "$1:$2,$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