name,date,size
name1,date1,120
name2,date2,140
name3,date3,150

##</code><code>##

use strict;
use Data::CTable;
use Statistics::Descriptive;

my $data = Data::CTable->new("data.txt");  # your csv file
$data->clean_ws();                         # clean up whitespace
my $sizecolumn  = $data->col('size');      # get column by name

my $stat = Statistics::Descriptive::Full->new();
$stat->add_data($sizecolumn);
print "sum of the column size:", $stat->sum() , "\n";