When i change the code from
$cnf{$c}=$_;
to 
push @{$cnf{$c} }, $_;
It doesn't work.
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MJD had some things to say about that:

• You cannot just paste code with no understanding of what is going on and expect it to work.
• Of course it doesn't work! That's because you don't know what you are doing!

• In my experience that is a bad strategy, because the people who ask such questions are the ones who paste the answer into their program without understanding it and then complain that it 'does not work'.
• You said 'It doesn't work'. The next violation will be punished by death.