I often have a list where I need to do adjacent pairs. 
my @trip =   ("Chicago", "Saint Looey", "Joplin", "OKC", "Amarillo", "
+Gallup",
                         "Flagstaff", "Winona", "Kingman", "Barstow", 
+"San Bernandino", "LA" );
map { printf  "%15s to %-15s\n", @trip[$_..$_+1]  } 0..$#trip-1;

[download]

which emits: 

        Chicago to Saint Looey    
    Saint Looey to Joplin         
         Joplin to OKC            
            OKC to Amarillo       
       Amarillo to Gallup         
         Gallup to Flagstaff      
      Flagstaff to Winona         
         Winona to Kingman        
        Kingman to Barstow        
        Barstow to San Bernandino 
 San Bernandino to LA

[download]

If you did this often, you might want a pairs_overlapping function. Or, going with a generic version:

subsequence(length=>3, step=>1, list=>\@trip);

[download]

a function that returns an arbitrary list of adjacent elements, with an arbitrary step size.

As to the next bit, I think several good solutions have been shown by others.

-QM
--
Quantum Mechanics: The dreams stuff is made of

In reply to Re: Fence vs. Posts by QM
in thread Fence vs. Posts by rodinski

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.