My approach, to ensure uniqueness in values, would be to make the values the keys of hash and then transform them into an array reference.

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my %hash;

while (<DATA>) {
    next unless /[^[:space:]]/; # make sure there's something on the l
+ine

    my ($key,$value)    = split;
    $hash{$key}{$value} = 0;
}

foreach my $key (keys %hash) {
    $hash{$key} = [keys %{$hash{$key}}];
}

print Dumper \%hash;

__DATA__
5    25
6    27
5    24
5    23
6    29
6    30
4    22
5    25
6    27
4    22
4    21

[download]

Update: Everyone seems to want to push the value on an array which doesn't get the "unique values" in the original request.

Cheers,
Ovid

New address of my CGI Course.
Silence is Evil (feel free to copy and distribute widely - note copyright text)

In reply to Re: Unique keys for multiple values with a Hash by Ovid
in thread Unique keys for multiple values with a Hash by Anonymous Monk

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.