Re^2: Confusion due to hash

reverse is useful to get the output in the desired format:

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

my %input = (10=>1, 20=>2, 30=>1, 40=>2);
my %output;

map { $output{ $input{ $_ } } += $_ } keys %input;

%output = reverse %output;

print Dumper \%output;
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Prints:

$VAR1 = {
          '60' => '2',
          '40' => '1'
        };
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Update: I paid to much attention to the requested output, and not enough to the note that he couldn't reverse the hash

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Re^3: Confusion due to hash by GrandFather (Saint) on Jan 31, 2006 at 01:51 UTC
Except that OP says And how do I check if a value exists? I can not reverse the hash since it has many of the same values. in which case leaving %rhash in its original form allows the lookup that OP wants - no reversing required. DWIM is Perl's answer to Gödel	[reply]