#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?i)<img.*?\/storage\/([^?]*).*?>"
Local $sString = "Random text <img style="width: 250px;" src="/storage/IMG_3843.JPG?__SQUARESPACE_CACHEVERSION=1413512531524" alt="" align="left" hspace="5" vspace="5"> more text"
Local $sSubst = "<img src="http://mydomainname.com/wp-content/uploads/$1">"
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