Hi Monks, I finally suceeded in doing it. it works as expected. Script (my_script.pl) is given below.

#!/usr/bin/perl

use strict;
use warnings;
use Time::Piece;
use POSIX qw(strftime);

my $format = '%b %e %T';

my $today = time;
my $formatted_today = strftime "%b %e %T", ( localtime($today) );

my $yesterday = $today - 60 * 24 * 60;
my $formatted_yesterday = strftime "%b %e %T", ( localtime($yesterday)
+ );

#print "VAR1 TODAY $today\n";
#print "VAR2 YESTERDAY $yesterday\n";
#print "\n";

#print "formatted_TODAY $formatted_today\n";
#print "formatted_YESTERDAY $formatted_yesterday\n";
#print "\n";

my $start = Time::Piece->strptime($formatted_yesterday, $format);
my $end   = Time::Piece->strptime($formatted_today, $format);

print "VARIABLE END TODAY $end\n";
print "VARIABLE START YESTERDAY $start\n";
print "\n";

open(FILE, "/var/log/maillog") or die "Couldn't open maillog: $!; abor
+ting";

while (<FILE>) {
    my ($timestamp) = /(^\w+\s+\d+\s+\d\d:\d\d:\d\d)/;
    my $t = Time::Piece->strptime($timestamp, $format);

    print if $t >= $start && $t <= $end;
}

close(FILE);
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