thanks again, but I don't really understand what context I can use this in  $hash {$thermos[3]}[0];! If i try to print it - nothing happens. If a print it within quotes, it thinks $hash is seperate to %hash and complains! How can I write a test; e.g. if $thermos[3] is equal to $some_value print the corresponding values $enthalpy and $entropy to $thermos[3]. thanks for your patience