This code build a new hash with the values as keys and collect all keys that point to this value. 
my %h = (
          a => 10,
          b => 10,
          c => 'd',
          e => 'd',
          f => 'a',
);

my %x;
while ( my ( $k, $v ) = each %h ) {
  push @{ $x{$v} }, $k;
}

__END__
$x = {

          'a' => [
                   'f'
                 ],
          '10' => [
                    'a',
                    'b'
                  ],
          'd' => [
                   'e',
                   'c'
                 ]
};

[download]
If you just want to remove the duplicates try: 
my %n = reverse %h;
%n = reverse %n;

[download]
Boris

In reply to Re: How to extract keyvalue pairs with duplicate values by borisz
in thread How to extract keyvalue pairs with duplicate values by august3

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.