use strict;
use warnings;

my (@list) = (1,1,2,3,4,4,4,5,6,7,7,8,9,10);

my %check;

foreach my $item (@list) {
	if (exists $check{$item}) {$check{$item}++;}
	else {$check{$item} = 1;}
}

foreach my $key (keys %check) {
	my $count = $check{$key};
	if ($count > 1) {
		print "$key was in the list $count times.\n";
	}
}