My reading of your post says you are looking for a one-to-many mapping in a hash. This is usually done with an array ref: perlreftut, perllol. Perhaps stored with:

push @{$hash{$key}}, $value;
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A hash cannot have keys repeated.

But maybe, while filling the hash with data, you want to find out if a key already exists in the hash.

That's not enough information for a useful answer. Considering your recent posts, please read, understand and follow How do I post a question effectively? and I know what I mean. Why don't you?

...
my %name_count;
for my  $name (values %names){
   $name_count{$name}++;
}
for my $name (sort {$name_count{$a}<=>$name_count{$b}} keys %name_coun
+t){
  print "$name occurs $name_count{$name} times in the \%names hash\n";
}
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It's also possible that codewalker wants to add the key "Name" to a hash three times, and wants to detect the collision and re-name the second and third keys to "Name2" and "Name3". Your guess is as good as mine, that's the problem!

My guess is that the OP wants to edit the values of an existing hash. Each value that is not unique should be made so by appending an integer.

use strict;
use warnings;
use Data::Dumper;
my %example = (
    a => 'red',
    b => 'blue',
    c => 'red',
    d => 'green',
    e => 'red',
);

my %desired = (
    a => 'red',
    b => 'blue',
    c => 'red1',
    d => 'green',
    e => 'red2',
);

       
my %seen;
while (my ($letter, $color) = each %example) {
    if ($seen{$color}++) {
        $example{$letter} = $color . $seen{$color};
        next;
    }
    $example{$letter} = $color
}
print Dumper( \%desired, \%example );
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UPDATE: Added example.

Bill

This is a minimalist answer, and is easily ambiguous:

Each value that is not unique should be made so by appending an integer.

Perhaps you mean something like:

Before inserting a hash key, if it already exists, string increment the key and try again.

-QM
--
Quantum Mechanics: The dreams stuff is made of