#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?um)(<p>\s*<\/p>\s*)+"
Local $sString = "ssdfsdfsdf<p> </p> <p></p> <p> </p><p> </p><p> </p><p> </p>sd<p> </p>fsdfs" & @CRLF & _
"ssdfsdfsd<p> </p><p></p> sdfssfd dfsd" & @CRLF & _
""
Local $sSubst = "<p><br/></p>"
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