#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(?<=auth\s-\s).*(?=(?:Firefox|Chrome)\/[\d\.]+)"
Local $sString = "::1 - OPTIONS - /signin - 204 - 0 - 0.163 ms http://localhost:8080/auth - Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36 -" & @CRLF & _
"" & @CRLF & _
"::1 - POST - /signin - 200 - 545 - 106.758 ms http://localhost:8080/auth - Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36 -" & @CRLF & _
"" & @CRLF & _
"::1 - OPTIONS - /signin - 204 - 0 - 0.126 ms http://localhost:8080/auth - Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:76.0) Gecko/20100101 Firefox/76.0 -"
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