#!/usr/bin/perl
#
# eg7: non-unique elements example, first version..
#

use strict;
use warnings;

my @array = ( 17, 5, 3, 17, 2, 5, 7, 6, 6, 10, 3 );

my %freq; map { $freq{$_}++ } @array;	# build element -> frequency hash
my %seen;				# what elements have we already seen?
my @nonuniq =   			# build distinct non-unique elements
	grep { $freq{$_} > 1 && ! $seen{$_}++ } @array;
my $str = join(',',@nonuniq); print qq($str\n);
