#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(st=([^& ]*)|)(.*c=([^& ]*)|)(.*t=([^& ]*)|)(.*k=([^& ]*)|) HTTP"
Local $sString = "st=expand&c=22&t=button&k=fun HTTP" & @CRLF & _
"c=22&t=button&k=fun HTTP" & @CRLF & _
"st=expand&c=22&t=party&k=fun HTTP" & @CRLF & _
"st=expand&c=22&k=fun HTTP" & @CRLF & _
"st=expand HTTP" & @CRLF & _
" HTTP"
Local $sSubst = "\2,\4,\6,\8"
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