Just grab them only the second time they're seen. 
my @result = do {
  my %counter;
  grep ++$counter{$_} == 2, @input;
};

[download]

-- Randal L. Schwartz, Perl hacker

In reply to •Re: Get All Duplicated Elements in an Array (Once, without shifting) by merlyn
in thread Get All Duplicated Elements in an Array (Once, without shifting) by George_Sherston

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