Hello, That code will work sice the list is only one. I want to count the occurence of the combination of the lists. and also to know how to map them. i have 3 lists @list1 ={sunny,windy} @list2 = {t,f,b} @list3 = {a,b} and i have records sunny t a sunny t b sunny f a sunny f a sunny b b windy f a windy f b and so on , so i want to know te occurence of all combinations of these records. then i want to count the occurence of sunny,t,a and sunny,t,b and sunny,f,a and sunny,f,b, windy,t,a, ..... so the hash should have multiple keys i.e from list1,list2,list3. and i could craete this as i have described in my question. but i dont know how to retrive. i.e i have an entry "sunny,f,b " how can i know its frequency. Please kindly let me know. Thanks