#!/usr/bin/perl
# your code goes here
use strict;
use warnings;
use Data::Dumper;
my %session_called = ();
for my $sid (qw/1 2 3 1 1 1 3 4 5 2/) {
session_called{$sid} ++;
}
print Dumper
(\%session_called) . "\n";
my @duped = grep { $session_called{$_} > 1 } keys %session_called;
print Dumper
(\@duped) . "\n";
IyEvdXNyL2Jpbi9wZXJsCiMgeW91ciBjb2RlIGdvZXMgaGVyZQoKdXNlIHN0cmljdDsKdXNlIHdhcm5pbmdzOwp1c2UgRGF0YTo6RHVtcGVyOwoKbXkgJXNlc3Npb25fY2FsbGVkID0gKCk7Cgpmb3IgbXkgJHNpZCAocXcvMSAyIDMgMSAxIDEgMyA0IDUgMi8pIHsKCXNlc3Npb25fY2FsbGVkeyRzaWR9ICsrOwp9CnByaW50IER1bXBlcihcJXNlc3Npb25fY2FsbGVkKSAuICJcbiI7CnByaW50IGpvaW4oJywnLCAoa2V5cyAlc2Vzc2lvbl9jYWxsZWQpKSAuICJcbiI7CgpteSBAZHVwZWQgPSBncmVwIHsgJHNlc3Npb25fY2FsbGVkeyRffSA+IDEgfSBrZXlzICVzZXNzaW9uX2NhbGxlZDsKCnByaW50IER1bXBlcihcQGR1cGVkKSAuICJcbiI7Cg==