Fences are a side effect of 'reduce'...

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=1216162
use warnings;
use List::AllUtils qw( reduce pairwise );

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

reduce { printf "%15s to %-15s\n", $a, $b; $b } @trip;

my @states =   ("IL", "MO", "MO", "OK", "TX", "TX",
  "AZ", "AZ", "AZ", "CA", "CA", "CA" );

my %info = pairwise { $a => { state => $b } } @trip, @states;

use Data::Dump 'dd'; dd \%info;

print "\n", $info{Joplin}{state}, "\n";
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Outputs:

        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             
{
  "Amarillo"       => { state => "TX" },
  "Barstow"        => { state => "CA" },
  "Chicago"        => { state => "IL" },
  "Flagstaff"      => { state => "AZ" },
  "Gallup"         => { state => "TX" },
  "Joplin"         => { state => "MO" },
  "Kingman"        => { state => "AZ" },
  "LA"             => { state => "CA" },
  "OKC"            => { state => "OK" },
  "Saint Looey"    => { state => "MO" },
  "San Bernandino" => { state => "CA" },
  "Winona"         => { state => "AZ" },
}

MO
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Indexes? We don't need no stinking indexes!