My script

//version=6
indicator("ISIN demo")

// Define inputs for two symbols to compare.
string symbol1Input = input.symbol("NASDAQ:AAPL", "Symbol 1")
string symbol2Input = input.symbol("GETTEX:APC", "Symbol 2")

if barstate.islastconfirmedhistory
// Retrieve ISIN strings for `symbol1Input` and `symbol2Input`.
var string isin1 = request.security(symbol1Input, "", syminfo.isin)
var string isin2 = request.security(symbol2Input, "", syminfo.isin)

// Log the retrieved ISIN codes.
log.info("Symbol 1 ISIN: " + isin1)
log.info("Symbol 2 ISIN: " + isin2)

// Log an error message if one of the symbols does not have ISIN information.
if isin1 == "" or isin2 == ""
log.error("ISIN information is not available for both symbols.")
// If both symbols do have ISIN information, log a message to confirm whether both refer to the same security.
else if isin1 == isin2
log.info("Both symbols refer to the same security.")
else
log.info("The two symbols refer to different securities.")