%%[
set @language = System_Language__c
Set @FRvalue= "fr_" 
/* Does it match; ; if no match, output of IndexOf(1,2) will be "0" */ 


if @language == "French" OR IndexOf(@language,@FRvalue) > 0 then 
Set @subjectline = "Vous êtes sur la liste pour recevoir les dernières nouvelles concernant Cat® Vantage" 
else 
Set @subjectline = "You're on the list for the latest news for Cat® Vantage Rewards!"
endif

]%%