#include <StringConstants.au3> ; to declare the Constants of StringRegExp
#include <Array.au3> ; UDF needed for _ArrayDisplay and _ArrayConcatenate
Local $sRegex = "access_token=(.*?)&expires=\d+"
Local $sString = "access_token=CAABletmsJHgBAEMfdJEgA1wEXgqwVgfM1nrTgyHq9XxkIEvLVGOUMq80ZBaA2ZA6Ndc18xNwZAJCDwpILNSKgGiVu4SIm9B0K5ocv7ZCVFV1bxKrNW9qrIqK1HKIz3uD6nO4RQnVgfVmLggoqZCVkPwjEY79ijZC0SYKPYM2RN9qg4TZB5E2iMz5WfAAACddAbXaEZCbzkBSoSZBTlEyea8rC&expires=5181509"
Local $aArray = StringRegExp($sString, $sRegex, $STR_REGEXPARRAYFULLMATCH)
; Present the entire match result
_ArrayDisplay($aArray, "Result")
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