#!/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";
IyEvdXNyL2Jpbi9wZXJsCiMgeW91ciBjb2RlIGdvZXMgaGVyZQoKdXNlIHN0cmljdDsKdXNlIHdhcm5pbmdzOwp1c2UgRGF0YTo6RHVtcGVyOwoKbXkgJXNlc3Npb25fY2FsbGVkID0gKCk7Cgpmb3IgbXkgJHNpZCAocXcvMSAyIDMgMSAxIDEgMyA0IDUgMi8pIHsKCSRzZXNzaW9uX2NhbGxlZHskc2lkfSArKzsKfQpwcmludCBEdW1wZXIoXCVzZXNzaW9uX2NhbGxlZCkgLiAiXG4iOwpwcmludCBqb2luKCcsJywgKGtleXMgJXNlc3Npb25fY2FsbGVkKSkgLiAiXG4iOwoKbXkgQGR1cGVkID0gZ3JlcCB7ICRzZXNzaW9uX2NhbGxlZHskX30gPiAxIH0ga2V5cyAlc2Vzc2lvbl9jYWxsZWQ7CgpwcmludCBEdW1wZXIoXEBkdXBlZCkgLiAiXG4iOwo=
$VAR1 = {
'2' => 2,
'5' => 1,
'1' => 4,
'4' => 1,
'3' => 2
};
2,5,1,4,3
$VAR1 = [
'2',
'1',
'3'
];