use Data::Dumper;
@ar=([1,1],[1,2],[3,5],[6,7]);

map {test($_->[0],$_->[1])} @ar;

sub test
{
	my ($k,$val)=@_;
	
	if (exists $hash{$k})
	{
		$hash{$k} .= ','.$val ;
	}
	else
	{
		$hash{$k}=$val;
	}
}

print Dumper(\%hash);



##</code><code>##

$VAR1 = {
          '6' => 7,
          '1' => '1,2',
          '3' => 5
        };