#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?mix)<img\s" & @CRLF & _
"(?=(?:[^>=]|='[^']*'|="[^"]*"|=[^'"][^\s>]*)*?\salt=['"]([^"]*)['"]?)" & @CRLF & _
"(?:[^>=]|='[^']*'|="[^"]*"|=[^'"\s]*)*"\s?\/?>"
Local $sString = "<a href="gallery.com/gallery-name"; target="_blank"> <img class="aligncenter" src="myblog.com/wp-content/image.jpg" alt=" I want to get this text" width =" 400 " height="300" /></a>" & @CRLF & _
"" & @CRLF & _
"" & @CRLF & _
"<img onmouseover=' alt="This is not the droid you are looking for" ;' class="aligncenter" src="myblog.com/wp-content/image.jpg" alt="This is the droid I'm looking for." width =" 400 " height="300" />"
Local $sSubst = "$1chat/$2"
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