#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "^\/board\/(.*)t(\d+)\.html$"
Local $sString = "/board/here-is-the-title-t1234.html"
Local $sSubst = "http://example.com/forum/$1$2 permanent;"
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