#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)\b([a-z])\1+(?!\1|\b)|(?<=([a-z]))((?!\2)[a-z])\3+"
Local $sString = "aaa baaab xxx" & @CRLF & _
"ahhj aaab cc iiik" & @CRLF & _
"bbb ahhj aaab cc iiik xxx fjjj baaaaaab yyyaaa"
Local $sSubst = "$1$3"
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