my $dbh = DBI->connect(
   'DBI:driver:database:host', 'user', 'pass',
   {RaiseError => 1, HandleError => \&bail_out},
);

##</code><code>##

my $dbh = DBI->connect(
   'DBI:driver:database:host', 'user', 'pass',
   {RaiseError => 1, HandleError => \&bail_out},
);

my $sql = qq{ SELECT COUNT(*) FROM profiles WHERE username=? };

# Original
#my $result = $sth->execute($username)
#  or bail_out('Error executing SELECT');

# Modified
# Note that 'or' clause is removed
my $result = $sth->execute($username);

$dbh->disconnect;

##</code><code>##

sub bail_out {
   my $dbh = shift;
   $dbh->disconnect
     or bail_out(msg => "Cannot disconnect from the database");
   # prints html message
   exit(0);
}