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]

Hope this helps!

# get content of the page, or die if get() fails
use LWP::Simple;
$content = get('http://www.example.com/some/document.txt');
if (defined $content) { print $content; }
else { die 'get() failed'; }


# get content of page, sending a custom useragent (browser name)
use URI::Fetch;
$object = URI::Fetch->fetch(
  'http://example.com/some/document.txt',
  UserAgent => 'Perl script'
) or die URI::Fetch->errstr;
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use IO::All;                                # Let the madness begin...
$html < io->http("www.google.com");         # Grab a web page
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use LWP::Simple;

my $data = get('http://www.jaywil.com/libsearch/SAMPLE.TXT');

open DATAFILE, '<', \$data;
while (<DATAFILE>) {
    print $_;
}
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The http protocol does not directly support what you're trying to do. It's designed to return an entire file specified in an http request, not parts of a file. The easiest solution would be to slurp a copy of the file into a variable. Here are a couple of ways using LWP::Simple.

use LWP::Simple;

# get file into variable
my $data = get('http://www.jaywil.com/libsearch/SAMPLE.TXT');

# print all at once
print $data;

# or break up and print line by line
 # update: to keep blank lines at eof see comment by ikegami below 
@lines = split(/\n/, $data);
for (@lines){
    print "$_\n";
}
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If for some reason you actually need to get the file one line at a time over http, you would need some help on the server side. If someone hasn't already written a module for this, you could write a cgi script that keeps state information and handles a few operations such as *open*, *read_line* and *close*. Basically you would be designing your own mini protocol to run over http.

You incorrectly defined a file as "a series of lines seperated by newlines", whereas it's really "a series of lines ending in newlines (except possibly the last one)".

split(/\n/, $data) doesn't work. It removes blank trailing lines.
split(/\n/, $data, -1) doesn't work either. It adds a blank line.
split(/^/m, $data, -1) works. Bonus: It doesn't remove the newline!

The last one can also be written as split(/^/m, $data) and special handling allows split(/^/, $data) to work too.

split(/\n/, $data) doesn't work. It removes blank trailing lines.

What is your definition of "doesn't work" here? The dropping of empty trailing fields in the case of the LIMIT parameter being 0 or not specified works as advertised in the split docs.

split(/\n/, $data, -1) doesn't work either. It adds a blank line.

Perl doesn't do this on my system:

>perl -MData::Dumper -e "$_=qq(1\n2\n3); print Dumper split /\n/,$_,-1
+"
$VAR1 = '1';
$VAR2 = '2';
$VAR3 = '3';

>perl -MData::Dumper -e "$_=qq(1\n2\n3\n); print Dumper split /\n/,$_,
+-1"
$VAR1 = '1';
$VAR2 = '2';
$VAR3 = '3';
$VAR4 = '';
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When you read your data from file on the other hand, you have to be careful that your editor does not hide a trailing newline on the display. (E.g. Vim, where you can't tell the difference, other than by an initial [noeol] in the status line.)