I'm unable to understand what exactly this code doing: exists $is_prime{$_} and $is_prime{$_} 

my %is_prime;
   @primes = grep { 
                ( exists $is_prime{$_} and $is_prime{$_} )
                or 
                ( $is_prime{$_} = is_prime($_) )
             } @numbers;

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I appreciate your time to read and answer and thank u in advance. :)

In reply to Unable to Understand grep and hash use for prime no. by shankonit

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