#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(const uint[138][26]?_t)(\s?\S+\s*) (\s*[0-9]*[xXa-fA-F0-9]*)$"
Local $sString = "const uint8_t T_SYN_3 23"
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