How to sum up values Dear all, Question about the sum function; the file structure is as follows: A|100 A|200 A|150 B|20 B|90 C|10 C|30 C|300 The result I want to obtain is to sum values in the second column  (columnB) for each particular letter in the first column (ColumnA); e.g.: A|450 B|100 C|330 I don't want to use hash structure because the input file is very large.  Is there any simple way to do that step-by-step: to sum up values in  columnB until the letter in columnA changes and print the result... Thanks in advance for any suggestion, Andrej #!/usr/bin/perl use strict; use warnings;   open FH1, "< test.txt" or die "Can't open file : $!"; while () {     chomp;     ($columnA,$columnB)=split /\\|/;     ... ??? } --  To unsubscribe, e-mail: beginners-unsubscribe@perl.org For additional commands, e-mail: beginners-help@perl.org http://learn.perl.org/