I'm not sure how you pick the 'rg' for a given two digit prefix. (e.g. Why is it 22 => rg1003 and not 22 => rg1000.) Do you pick the most popular 'rg' for the given prefix? If so, the following will do the trick: 

my %pop;

++$pop{substr($_, 0, 2)}{$numbers{$_}}
   foreach keys %numbers;


my %most_pop;

foreach my $short (keys %pop) {
   my $short_pop = $pop{$short};
   my ($most_pop) = sort { $short_pop->{$b} <=> $short_pop->{$a} }
                    keys %$short_pop;
   $most_pop{$short} = $most_pop;
}


my %filtered;

foreach (keys %numbers) {
   my $key      = $_;
   my $rg       = $numbers{$_};
   my $short    = substr($_, 0, 2);
   my $most_pop = $most_pop{$short};

   if ($rg eq $most_pop) {
      $filtered{$short} = $most_pop;
   } else {
      $filtered{$key} = $rg;
   }
}

print("$_ => $filtered{$_}\n")
   foreach sort keys %filtered;

[download]

In reply to Re: summarization of list by ikegami
in thread summarization of list by gman

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.