my $dbh = DBI->connect("DBI:.....");
unless ($dbh) {
  die "Error in connecting to database: $DBI::errstr\n";
}

my $statement1 = "SELECT * FROM table1";
my $statement2 = "SELECT * FROM table2";
# ...
my $sth1 = $dbh->prepare($statement1)
  or die "Error in preparing Statement: ", $dbh->errstr(), "\n$statement1\n\n";

my $sth2 = $dbh->prepare($statement2)
  or die "Error in preparing Statement: ", $dbh->errstr(), "\n$statement2\n\n";

$sth1->execute() or die ...;
$sth2->execute() or die ...;

...