As stated before, this "divide and conquer" (also see http://en.wikipedia.org/wiki/Divide_and_conquer_algorithm) approach can be applied to many problems, but you can also use hashes for this by maintaining your order in the values as such: 
#!/usr/bin/perl

@a = qw(one two three);
%h = map({$_ => $count++} @a);
print "$_ => $h{$_}\n" foreach (keys(%h));
foreach (sort( {$h{$a} <=> $h{$b}} keys(%h))) {
   print "$_\n";
}

[download]

Janitored by tye: Add CODE tags

In reply to Re: "Swarming" by Anonymous Monk
in thread "Swarming" by kwaping

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.