To implement rovf's suggestion:

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

my %hash;

assignWithDupes([
    "one" => "1",
    "two" => "2",
    "one" => "3",
    "three" => "4",
    "two" => "5",
    "one" => "6",
],
\%hash);

print Dumper(\%hash);

sub assignWithDupes {
    my ($arr, $hash) = @_;
    my ($i, $j, $key, $val);
    
    for ($i = 0; $i < $#$arr; $i += 2) {
        $key = $arr->[$i];
        $val = $arr->[$i+1];
        
        if (!defined $hash->{$key}) {
            $hash->{$key} = $val;
            next;
        }

        for ($j = 2; defined $hash->{"${key}_$j"}; $j++) {}
        $hash->{"${key}_$j"} = $val;
    }
}

[download]

Output (modified to put it in order): 

$VAR1 = {
          'one' => '1',
          'one_2' => '3',
          'one_3' => '6'
          'two' => '2',
          'two_2' => '5',
          'three' => '4',
        };

[download]

As you can see, successive instances of the same key are assigned to _2, _3, etc.

In reply to Re^3: Throw compilation error(or warning) if duplicate keys are present in hash by TJPride
in thread Throw compilation error(or warning) if duplicate keys are present in hash by I_love_perl

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.