I wonder if it actually matters the these numbers are dates at all. If the filenames contain the date in the same format that you are using as arguments, then you could do something along the lines of this:

#!/usr/bin/perl -w

use strict;

my ($from, $to);

die "Invalid args\n" unless @ARGV;

unless (($from, $to) = $ARGV[0] =~ /(\d{8})-(\d{8})/) {
  die "Invalid args\n";
}

my $dir = '.';
opendir(DIR, $dir) or die "Can't open $dir: $!\n";

my @files =
  grep { /(\d{8})/ && $1 >= $from && $1 <= $to } readdir DIR;

print "@files\n";
[download]

An example:

> ls
date.pl           file20001105.txt  file20010101.txt
file20000907.txt  file20001231.txt  file20010215.txt
> ./date.pl 20010101-20010228
file20010101.txt file20010215.txt
>
[download]

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<http://www.dave.org.uk>

"Perl makes the fun jobs fun
and the boring jobs bearable" - me