#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)path.+?(?:foo=(\d+))(?![a-zA-Z\d])|path((?!foo).)*$"
Local $sString = "path?foo=67 " & @CRLF & _
"path?foo=67&bar=hello " & @CRLF & _
"path?bar=bye&foo=1&baz=12" & @CRLF & _
"path?bar=123" & @CRLF & _
"path" & @CRLF & _
"path?foo=37signals" & @CRLF & _
"path?foo=-8" & @CRLF & _
"something?foo=1" & @CRLF & _
"pathfoo" & @CRLF & _
""
Local $sSubst = ""
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