Question

Can anybody tell me how to push a duplicate element of an array to a new array?
This is what I have till now, again I want to retain the duplicate elements into a new array.

%seen = ();
@uniq = ();
foreach $item (@list) {
    unless ($seen{$item}) {
        $seen{$item} = 1;
        push(@uniq, $item);
    }
}
print "@unique\n";

Answer 1

If you’re trying to find values that appear more than once:

my @seen;
my @dups = grep ++$seen{$_} == 2, @list;

@list = qw( foo bar baz foo foo moo bar );
  gives
@dups = qw( foo bar );

---

If you’re trying to put the values that are only found once in @uniq and values that are found twice or more in @dups:

my %counts; 
++$counts{$_} for @list;

my (@uniq, @dups);
for (@list) {
   my $count = $counts{$_};
   push @uniq, $_ if $count == 1;
   push @dups, $_ if $count == 2;
}

@list = qw( foo bar baz foo foo moo bar );
  gives
@uniq = qw( baz moo );
@dups = qw( foo bar );

---

If you’re trying to put the first instance of a value in @uniq and the second and subsequent values in @dups:

my (@uniq, @dups, %seen);
push @{ $seen{$_}++ ? \@dups : \@uniq }, $_ for @list;

@list = qw( foo bar baz foo foo moo bar );
  gives
@uniq = qw( foo bar baz moo );
@dups = qw( foo foo bar );