use Modern::Perl;
use DBI;

my $dbh = DBI->connect(
    "dbi:CSV:",
    "", "",
    {
        f_dir        => './DB',
        csv_sep_char => "\t",
    }
) or die "Cannot connect: $DBI::errstr";

my $sql =
'SELECT id, count(*) AS number, sum(tumor) AS tumorscore, sum(normal) AS normalscore, sum(tumor - normal) AS difference, avg(tumor - normal) AS averagedifference FROM methyl WHERE (tumor - normal) <=20 or (tumor - normal) >=20 GROUP BY id ORDER BY id';

my $sth = $dbh->prepare($sql);
$sth->execute;
while ( my $row = $sth->fetchrow_hashref ) {
    say
"id: $row->{'id'}, Count: $row->{'number'}, Score tumor: $row->{'tumorscore'}, Score normal: $row->{'normalscore'}, Difference: $row->{'difference'}, Average Difference: $row->{'averagedifference'}";
}