Thank you for the reply , You are getting the correct output because you are probably providing the input to the program in different way then I am , your observation is correct , actually what's happening is that I am using the values in the array @words as keys in hash %count , now keys in hash are unique , but as you mentioned correctly that there are 2 "Perl" values , one with a newline and one without a newline , so it is treating them as separate keys , seems like chomp is not working on all the values , it's only removing newline from 1st input value. I have got the reason why my output is not correct because every line contains CRLF at the end and chomp(in my case) is removing only LF and keeping CR as correctly mentioned by @haukex