#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(https?\:\/\/.+?\.webm)\h"
Local $sString = "waka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm wakawaka http://video.webmfiles.org/big-buck-bunny_trailer.webm waka"
Local $sSubst = "<video width="320" height="240" controls><source src="$1" type="video/webm"></video>"
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