Use LWP::Simple to get the file, using getstore, then open it and read it thusly.

something like this (untested):

#!/usr/bin/perl -w

use strict;
use LWP::Simple;

my $content = getstore("http://www.jaywil.com/libsearch/SAMPLE.TXT", $
+your_file_name);

open(DATAFILE, $yourfilename);
# your file manipulation code here
[download]

Where $yourfilename is the name of the file and location of where you want your file to be.

Hope this helps!