First of all, have you seen how Perlmonks tries to format your log file example? Maybe you should put your log file inside code tag as well.

Secondly, and more relevant to your question, your variable $yesterday contains the time it was exactly 24 hours ago. Yesterday contained 24 * 60 * 60 = 86400 seconds, and $yesterday covers exactly one of those - therein lies the basis of your problem.

One way (of many) to solve this, is to calculate two values - $yesterday_start and $yesterday_end, and then check if the time stamp of the line in the log file lies between these two values. DateTime might prove useful. But beware of edge cases such as those days that switch from or to DST and other tricky business like that.

Another way could be to take $yesterday the way you do it now, and strip off the time information so that you only hold the date information. That's probably the easiest, because except for the way you obtaini $yesterday your code can run unaltered. But again, be careful that you don't run into problems on days that DST ends.

And finally, these days the three-arguments open (which you already use) with lexical filehandles is recommended. See perldoc open.

thank you for your time I used your advice and changed how I was getting the value of $yesterday and formatted it to match my log file, which made counting the hits a lot simpler.

my $yesterday = strftime("%d/%b/%Y",localtime(time()-86400));

Perhaps the following will help:

use strict;
use warnings;
use Time::Piece;
use Time::Seconds qw(ONE_DAY);

my $yesterday = localtime() - ONE_DAY();

my $mergedYesterday = join '/', ( split ' ', $yesterday )[ 2, 1, 4 ];

while (<DATA>) {
    my ($date) = /\[([^:]+)/; # Capture date, e.g., 11/Nov/2012
    $date =~ s/^0//; # Remove leading zero: 08/Oct/2007 -> 8/Oct/2007
    print if $date eq $mergedYesterday;
}

__DATA__
66.249.65.107 - - [11/Nov/2012:19:33:01 -0400] "GET /support.html HTTP
+/1.1" 200 11179
111.111.111.111 - - [11/Nov/2012:19:33:01 -0400] "GET / HTTP/1.1" 200 
+10801
111.111.111.111 - - [08/Oct/2007:11:17:55 -0400] "GET /style.css HTTP/
+1.1" 200 3225
123.123.123.123 - - [26/Apr/2000:00:23:48 -0400] "GET /pics/wpaper.gif
+ HTTP/1.0" 200 6248
123.123.123.123 - - [26/Apr/2000:00:23:40 -0400] "GET /asctortf/ HTTP/
+1.0" 200 8130
123.123.123.123 - - [26/Apr/2000:00:23:48 -0400] "GET /pics/5star2000.
+gif HTTP/1.0" 200 4005
123.123.123.123 - - [26/Apr/2000:00:23:50 -0400] "GET /pics/5star.gif 
+HTTP/1.0" 200 1031
123.123.123.123 - - [26/Apr/2000:00:23:51 -0400] "GET /pics/a2hlogo.jp
+g HTTP/1.0" 200 4282
123.123.123.123 - - [26/Apr/2000:00:23:51 -0400] "GET /cgi-bin/newcoun
+t?jafsof3&width=4&font=digital&noshow HTTP/1.0" 200 36
172.16.130.42 - - [26/Apr/2000:00:00:12 -0400] "GET /contacts.html HTT
+P/1.0" 200 4595
10.0.1.3 - - [26/Apr/2000:00:17:19 -0400] "GET /news/news.html HTTP/1.
+0" 200 16716
129.21.109.81 - - [26/Apr/2000:00:16:12 -0400] "GET /download/windows/
+asctab31.zip HTTP/1.0" 200 1540096
192.168.198.92 - - [22/Dec/2002:23:08:37 -0400] "GET / HTTP/1.1" 200 6
+394
192.168.198.92 - - [22/Dec/2002:23:08:38 -0400] "GET /images/logo.gif 
+HTTP/1.1" 200 807
192.168.72.177 - - [22/Dec/2002:23:32:14 -0400] "GET /news/sports.html
+ HTTP/1.1" 200 3500
192.168.72.177 - - [22/Dec/2002:23:32:14 -0400] "GET /favicon.ico HTTP
+/1.1" 404 1997
192.168.72.177 - - [04/Nov/2012:23:32:15 -0400] "GET /style.css HTTP/1
+.1" 200 4138
192.168.72.177 - - [22/Dec/2002:23:32:16 -0400] "GET /js/ads.js HTTP/1
+.1" 200 10229
192.168.72.177 - - [22/Dec/2002:23:32:19 -0400] "GET /search.php HTTP/
+1.1" 400 1997
127.0.0.1 - - [10/Apr/2007:10:39:11 +0300] "GET / HTTP/1.1" 500 606
127.0.0.1 - - [10/Apr/2007:10:39:11 +0300] "GET /favicon.ico HTTP/1.1"
+ 200 766
139.12.0.2 - - [10/Apr/2007:10:40:54 +0300] "GET / HTTP/1.1" 500 612
139.12.0.2 - - [10/Apr/2007:10:40:54 +0300] "GET /favicon.ico HTTP/1.1
+" 200 766
127.0.0.1 - - [10/Apr/2007:10:53:10 +0300] "GET / HTTP/1.1" 500 612
127.0.0.1 - - [10/Apr/2007:10:54:08 +0300] "GET / HTTP/1.0" 200 3700
127.0.0.1 - - [10/Apr/2007:10:54:08 +0300] "GET /style.css HTTP/1.1" 2
+00 614
127.0.0.1 - - [10/Apr/2007:10:54:08 +0300] "GET /img/pti-round.jpg HTT
+P/1.1" 200 17524
127.0.0.1 - - [10/Apr/2007:10:54:21 +0300] "GET /unix_sysadmin.html HT
+TP/1.1" 200 3880
217.0.22.3 - - [04/Nov/2012:10:54:51 +0300] "GET / HTTP/1.1" 200 34
217.0.22.3 - - [10/Apr/2007:10:54:51 +0300] "GET /favicon.ico HTTP/1.1
+" 200 11514
217.0.22.3 - - [10/Apr/2007:10:54:53 +0300] "GET /cgi/pti.pl HTTP/1.1"
+ 500 617
127.0.0.1 - - [10/Apr/2007:10:54:08 +0300] "GET / HTTP/0.9" 200 3700
217.0.22.3 - - [10/Apr/2007:10:58:27 +0300] "GET / HTTP/1.1" 200 3700
217.0.22.3 - - [10/Apr/2007:10:58:34 +0300] "GET /unix_sysadmin.html H
+TTP/1.1" 200 3880
217.0.22.3 - - [10/Apr/2007:10:58:45 +0300] "GET /talks/Fundamentals/r
+ead-excel-file.html HTTP/1.1" 404 31
[download]

Output:

66.249.65.107 - - [11/Nov/2012:19:33:01 -0400] "GET /support.html HTTP
+/1.1" 200 11179
111.111.111.111 - - [11/Nov/2012:19:33:01 -0400] "GET / HTTP/1.1" 200 
+10801
[download]

The join:

my $mergedYesterday = join '/', ( split ' ', $yesterday )[ 2, 1, 4 ];
          ^                 ^                     ^        ^  ^  ^ 
          |                 |                     |        |  |  | 
          |                 |                     |        |  |  + - 2
+012
          |                 |                     |        |  + - Nov
          |                 |                     |        + - 11
          |                 |                     + - Sun Nov 11 19:31
+:46 2012
          |                 + - Use same delimiter as in log records
          + - 11/Nov/2012
[download]

The capturing regex

/\[([^:]+)/;
  ^   ^
  |   |
  |   + - Capture everything up to the first colon, e.g., 11/Nov/2012
  + - Anchor at left bracket
[download]

use POSIX qw(strftime);

$time= localtime(time-(24*60*60));
$yesterday = strftime( '%d/%m/%y', $time);
[download]

`grep "$yesterday" logfile.log | wc -l`
[download]

Number of lines returned is the number of hits on your site. This command can be run inside a Perl script inside backticks.

However, the grep command exists in Perl too, so just read the file into an array and use the Perl grep command, as in scalar context it returns the number of matches.

open(LOGFILE,"<", "access.log")or die"Could not open log file.";
my @logfile = <LOGFILE>
my $hits = grep /$yesterday/, @logfile;
[download]

close(LOGFILE);

open(WEBPAGE,">",$webPage);
$tm = strftime( "%d/%m/%Y", localtime());
 

    print WEBPAGE <<EOF; 
<head><title>Access Counts</title>
</head>
<body>
<h1> today is: $tm</h1>
<h3>Yesterday was $yesterday</h3>
<table border="1" cellpadding="10" width='500px'>
<h2>Total hits: $totalhits</h2>
<h3>Hits Yesterday: $yesterdayHits</h3>
$rows
</table></p>
</body>
</html>
EOF

close( WEBPAGE);
[download]

Basic CGI can even make the html a lot better, like so:

     ...
use CGI qw(:standard);

my $q = CGI->new;
print $q->start_html( -title => 'Yesterday Hits' ),
      $q->h1("today is: $tm"), 
      $q->h3("Yesterday was $yesterday"),
      $q->table(
          { border => '1', cellpadding => '10', width => '500' },
          Tr( td("Total Hits: $totalhits"), td("Hits Yesterday: $yeste
+rdayHits"), )
      ),
      $q->end_html;
[download]