Remember that [] is used to reference to an array element and a {} is for a hash. So you need to change your code to:

#                              v
$records{"$owner_record[1]"} = { 
            USER => "$owner_record[5]", 
            FILENAME => "$owner_record[0]",  
            PID => "$owner_record[6]", 
            TIME => "$owner_record[9]", 
            DATE => (join ":", "$owner_record[10] $owner_record[11]"),
+ 
            ELAPSED => [] 
        };
#       ^
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