#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "\[\s*youku\s*:\s*([^]]*)\]"
Local $sString = "Hello [youku: xxAAAJFSK] This is a test." & @CRLF & _
"Hello2 This is test2 [ youku : y8d78fd]." & @CRLF & _
"Hello3 This is test3 [ youku" & @CRLF & _
"" & @CRLF & _
": 484fsfs]."
Local $sSubst = "<iframe src="http://player.youku.com/embed/$1"></iframe>"
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