#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(?<=<\/a>)(\w+)"
Local $sString = "<a href="blah.com">Hello</a>World // Here we need to put space between Hello and World" & @CRLF & _
"" & @CRLF & _
"<a href="blah.com">Hello</a> World // Do not touch this" & @CRLF & _
"" & @CRLF & _
"<a href="blah.com">Hello</a><b>World</b> // do not touch this"
Local $sSubst = " $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