$DSN= 'dbi:DriverName:database=$db;host=$host;port=$port;'

##</code><code>##

$sth = $dbh->do('SELECT whatever ...');

##</code><code>##

my $sql = 'SELECT whatever ...';
print "Statement: [$sql\n]";
$sth = $dbh->do($sql);

##</code><code>##

use Data::Dumper;
...
my $sql = 'SELECT whatever ...';
print Dumper $sql;
my $sth = $dbh->prepare($sql) or die "prepare failed: ', $DBI::errstr;
...