Combining your loops into one: 
my @a = qw/ 1 2 3 4 5 6 7 8 9 5 7 9 5 /;
my %seen;
my @dups = grep ++$seen{$_}==2, @a;
print "@dups\n";

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In reply to Re^2: What is the best way to get just the duplicates from an array? by ikegami
in thread What is the best way to get just the duplicates from an array? by wenD

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