Seems like a lot of complicated and expensive solutions are being offered for a problem that is very simple.

NO duplicated arrays or mashed together strings and expensive regex iterations; just one line of standard perl:

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @trip =   ("Chicago", "Saint Looey", "Joplin", "OKC", "Amarillo", "
+Gallup", "Flagstaff", "Winona", "Kingman", "Barstow", "San Bernandino
+", "LA" );

printf "%15s to %-15s\n", @trip[ $_-1 .. $_ ] for 1 ..  $#trip;

__END__
C:\test>junk38
        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]