You need to grab the column names manually:

my $sth = $dbh->prepare($sql);
$sth->execute() || die $sth->errstr;

my $columns = $sth->{NAME};
print IN join( "\t", @{ $columns } ), "\n";

while ( my @row = $sth->fetchrow_array ) {
    print IN join("\t", @row), "\n";
}
[download]

Chris
M-x auto-bs-mode