2009-12-22,174865.6853,171
2009-12-23,158423.1442,155
2009-12-24,146650.9855,143
2009-12-25,127228.4832,124
2009-12-26,179032.6644,175
2009-12-27,179770.0221,176
2009-12-28,153049.9829,149
2009-12-29,159508.811,155
2009-12-30,75322.9348,143
2009-12-31,184494.3142,124
2010-01-01,88085.89262,87
2010-01-02,157525.6179,204
2010-01-03,213673.8187,214
2010-01-04,190080.1713,198
2010-01-05,139624.0644,155
2010-01-06,159684.3982,180
2010-01-07,159508.811,91
2010-01-08,75322.9348,130
2010-01-09,174867.4572,207
2010-01-10,206403.5704,86
2010-01-11,121876.6863,154
2010-01-12,89091.60969,209
2010-01-13,159684.3982,180
2009-01-14,153049.9829,149

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;


# source file directory.
my $srcdir = "../source";

# source file name.
my $srcfile = $srcdir."/vol.dat"; 

# Open source file in READ mode.
open (READ, "< $srcfile") || die "Can't find the DAT file\n";


################## Start date time i.e. the first day of the last 30 days, is calculated by this code.
my $epochToday1 = time;
$epochToday1 = $epochToday1 - 2592000;
my ($year1, $month1, $day1) = (localtime($epochToday1))[5,4,3];
$month1++;
$year1+=1900;

my $startdate = $year1."-".$month1."-".$day1;
########################

################## End date time i.e. the current day, is calculated by this code.
my $epochToday2 = time;
my ($year2, $month2, $day2) = (localtime($epochToday2))[5,4,3];
$month2++;
$year2+=1900;

my $enddate = $year2."-".$month2."-".$day2;
########################

# Destination Directory.
my $desdir = "../target";

#destination File name.
my $desfile = $desdir."/total_volume_last30days.csv";

#Open target file in Write mode.
open (WRITE, "> $desfile") || die "Can't find the CSV file.\n";

# Print the headers for the Report in CSV.
my @headers = ("Date",",","Total_Volume");
print WRITE @headers,"\n";


my $printout; 		#declaration of variable which prints in the Target file.

while (<READ>)	
{
	my $start = $startdate;
	my $end  = $enddate;
	
	if ( /^$start/ .. /^$end/ ) 		#range to be checked and written to Target file.
	{
		chomp;
		my (@items) = split (/,/,$_);
		
		my $tot = $items[1]+ $items[2];	#sum of incoming an outgoing bytes.
		$printout .= "$items[0],$tot \n";		#variable which stores the Data to be written in target file.

    }	
}

print WRITE $printout; 							#write $printout values to Target file. 
close READ || die "Couldn't close the DAT file";		#close input file.
close WRITE || die "Couldn't close the CSV file";		#close target file.
exit  0;

##</code><code>##

Use of uninitialized value $printout in print at total_volume_last30.pl line 67,
 <READ> line 122.