Since your dates are in YYYYMMDDHH format you can use string comparisons to decide whether the datum is in the correct range. This script decrements the current epoch time value by the relevant number of seconds needed to go back to the Friday of the previous week and then another four days to get to the Monday. It then constructs start and end timestamp strings for hour 0 of the Monday and hour 23 of the Friday.

use strict;
use warnings;

my %daysOffsetTV = (
   0 => 86400 * 2,
   1 => 86400 * 3,
   2 => 86400 * 4,
   3 => 86400 * 5,
   4 => 86400 * 6,
   5 => 86400 * 7,
   6 => 86400,
   );

my $nowTV = time();
my $dayOfWk = ( localtime( $nowTV ) )[ 6 ];

my $prevWkFriTV = $nowTV - $daysOffsetTV{ $dayOfWk };
my( $friDay, $friMth, $friYr ) =
   ( localtime( $prevWkFriTV ) )[ 3 .. 5 ];
$friMth += 1;
$friYr  += 1900;
my $endDate =
   sprintf q{%04d%02d%02d%02d}, $friYr, $friMth, $friDay, 23;

my $prevWkMonTV = $prevWkFriTV - 86400 * 4;
my( $monDay, $monMth, $monYr ) =
   ( localtime( $prevWkMonTV ) )[ 3 .. 5 ];
$monMth += 1;
$monYr  += 1900;
my $startDate =
   sprintf q{%04d%02d%02d%02d}, $monYr, $monMth, $monDay, 0;

print
   qq{Starting date: $startDate\n},
   qq{  Ending date: $endDate\n\n};

while( <DATA> )
{
    my $timestamp = ( split m{,} )[ 0 ];
    print
       unless $timestamp lt $startDate or $timestamp gt $endDate;
}

__END__
2009030822,3558,1.68
2009030823,6385,5.47
2009030900,7485,1.82
2009030901,8563,4.35
2009031322,8860,3.68
2009031323,39224,14.16
2009031400,34553,7.34
2009031401,7353,5.74
[download]

The output.

Starting date: 2009030900
  Ending date: 2009031323

2009030900,7485,1.82
2009030901,8563,4.35
2009031322,8860,3.68
2009031323,39224,14.16
[download]

I hope this is of interest.

Cheers,

JohnGG