Have a look at How can I extract just the unique elements of an array? (FAQ).

In your case, you could use one of those methods to strip out the duplicates before the foreach loop, or you could integrate a method into the loop itself sort of like this: 

my %unique_urls;
foreach (@links) {
    if ($links[$i]->url() =~ m!(-[0-9][0-9][0-9][0-9][0-9][0-9]*)!) {
        $links[$i]->url() =~ m!([0-9][0-9][0-9][0-9][0-9][0-9]*)!;
        my $url = $1;
        $art[$i] = $url;
        print "$url\n" if ( ! $unique_urls{$url}++ );
    }
    $i++;
}

[download]

I recommend something like this: 

my %unique_urls;
my @art = grep { m{-(\d{5,})} && !$unique_urls{$1}++ }
          map { $_->url() } $agent->links();
undef %unique_urls;
print map { "$_\n" } @art;

[download]

That may be diverging too much from your original intention, though. It's hard to recommend with confidence without reading the context.

In reply to Re: Help needed with mechanize by kyle
in thread Help needed with mechanize by lazybowel

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.