print "Please enter the last name:\n";
my $user_data = <>;
chomp $user_data;

$DBH->do("select * from people where last_name='$user_data'");

##</code><code>##

Jones'; drop table people; --

##</code><code>##

print "Please enter the last name:\n";
my $user_data = <>;
chomp $user_data;

my $STH = $DBH->prepare("select * from people where last_name=?");
$STH->execute($user_data);

##</code><code>##

print "Please enter the file name:\n";
my $user_data = <>;
open my $FH, '<', $user_data;
while (my $last_name = <$FH>) {
    chomp $last_name;
    my $STH = $DBH->prepare("select * from people where last_name=?");
    $STH->execute($last_name);
}

##</code><code>##

print "Please enter the file name:\n";
my $user_data = <>;
open my $FH, '<', $user_data;
my $STH = $DBH->prepare("select * from people where last_name=?");
while (my $last_name = <$FH>) {
    chomp $last_name;
    $STH->execute($last_name);
}