Welcome to perl!

Stick with it. It is useful for so many things and there is help to be had in many places.

I've provided you with some code for tutorial purposes but I'd recommend going with Mikes because it is more elegant and versatile.

The script below works on files in the current directory containing the perl script.

For information on $|, visit Suffering from Buffering. It basically makes sure your output comes out as expected.

For more information on perl, such as the localtime() and stat(), functions, checkout perl.org and your local ActiveState documentation and, of course, Google is your friend.

use strict;
use warnings;
$|=1; # Buffering

my @filenames;

opendir DIR, "." or die "Failed while trying to open current directory
+\nPerl says: \n$!";
@filenames = readdir DIR; # Get list of files in current directory
shift @filenames; shift @filenames; # remove . and ..

foreach (@filenames) {
    my $mtime = (stat($_))[9]; # Get mtime for file
    my $year = (localtime($mtime))[5] + 1900; # Get year for file
    my $month = (localtime($mtime))[4] +1; # Get month for file
    my $day = (localtime($mtime))[3]; # Get day of month for file
    if ($month >= 03 and $year == "2013") {
         if ($month == 03 and $day >=20) { print "Filename: $_\n"; }
         if ($month == 04 and $day <=21) { print "Filename: $_\n"; }
    }
}
[download]

The code to drop in your script might be: (Warning: Not tested)

my @filenames = parse_dir($ls);

foreach (@filenames) {
    my $mtime = (stat($_))[9]; # Get mtime for file
    my $year = (localtime($mtime))[5] + 1900; # Get year for file
    my $month = (localtime($mtime))[4] +1; # Get month for file
    my $day = (localtime($mtime))[3]; # Get day of month for file
    if ($month >= 03 and $year == "2013") {
         if ($month == 03 and $day >=20) { print "Filename: $_\n"; }
         if ($month == 04 and $day <=21) { print "Filename: $_\n"; }
    }
}
[download]