How am I suppose to use your program?

• This clobbers any existing listurls.txt, gives me two copies of the data and puts a useless status message in preferedname.txt:

  linkextractor http://www.blah.com/ > preferedname.txt
  [download]

• This clobbers any existing listurls.txt and puts a useless status message in urls.txt:

  linkextractor http://www.blah.com/ > preferedname.txt & del listurls.t
  +xt
  [download]

• This clobbers any existing listurls.txt and loses any error status message:

  linkextractor http://www.example.com/ > nul & move listurls.txt prefer
  +edname.txt
  [download]

Suggestions:

• Don't say it's OK when it isn't. Use the correct message.
• Don't say it's OK when it is. Only send the URIs to STDOUT.
• Send error messages (incl non 200 status messages) to STDERR.
• Convert the URIs to absolute URIs.
• Remove duplicate URIs.
• Replace my $url = <@ARGV>; with my ($url) = @ARGV;.
• The domain www.example.com (among others) was set aside for examples. It's better to use that than www.blah.com, a real live domain.

Suggestions applied:

use strict;
use warnings;

use List::MoreUtils qw( uniq );
use WWW::Mechanize  qw( );

# usage: linkextractor http://www.blah.com/ > listurls.txt
my ($url) = @ARGV;

my $mech = WWW::Mechanize->new();
my $response = $mech->get($url);
$response->is_success()
   or die($response->status_line() . "\n");

print map { "$_\n" }
      sort { $a cmp $b }
      uniq
      map { $_->url_abs() }
      $mech->links();
[download]

Update: At first, I didn't realize it was outputing to STDOUT in addition to listurls.txt. I recommended that the output should be sent to STDOUT. This is a rewrite.