You could solve both problems in one go by temporarily inverting your hash. So instead of a (state => cities) hash, you have a (city => state) hash. Then you can invert it back.

use strict;
use warnings;
use Data::Dumper;

my %hash = (
  'Alabama'    => ['Andalusia','Anniston','Clanton','Eufaula','Auburn'
+,'Auburn','Auburn','Auburn'],  
  'California' => ['Barstow','Eufaula'],
  'New York'   => ['Amsterdam','Coney Island','Beacon','Beacon','Beaco
+n','Beacon','Beacon'],
  'Utah'       => ['Beacon','Layton'],
);

# Invert the hash.
my %inverted = map {
    my $state = $_;
    map { $_ => $state } @{$hash{$state}}
} sort keys %hash;

print Dumper \%inverted;

# And back again:
%hash = ();
while (my ($city, $state) = each %inverted) {
    push @{ $hash{$state} ||= [] }, $city;
}

print Dumper \%hash;

[download]

In reply to Re^2: Hash Multiple values for a key-Filtering unique values for a key in hash by tobyink
in thread Hash Multiple values for a key-Filtering unique values for a key in hash by rahulme81

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.