Pulling First Names From Database

I am new to CGI and Perl so please be patient with me if I ask some dumb questions. I have a form that requests an email address and password. Upon clicking the Submit button I want to connect to the database, find the email address in the table and return a page displaying the first name of the client. I'm using Apache to test the script, so it isn't uploaded to my server for public viewing, but if it helps I will gladly do so. The script I have so far, connects to the db, but it doesn't return any names. Here the script I have so far:

#!/perl/bin/perl

use CGI qw(:standard);
use CGI::Carp qw(fatalsToBrowser);
use DBI;
use Time::Local

print header;
# Page title on top of webpage
print start_html("Client Login");

# delcare fields
my($mail_id, $password_id, $client_id, $fname);

# Connect to the database
my $DSN = 'driver=Microsoft Access Driver (*.mdb);dbq=C:\Documents and Settings\Mike\My Documents\My Website\Clients.mdb';
my $dbh = DBI->connect("DBI:ODBC:$DSN")
or die "$DBI::errstr\n";
$::db_host = 'localhost';
$::db_name = 'Clients.mdb';
$::db_user = 'root';

# The SQL that I want to run
# 1st, get the client_id for the mail_id entered on the form
my $sth = $dbh->prepare("SELECT client_id FROM tblClients WHERE mail_id = '$mail_id'")
or die "prepare failed: " . $dbh->errstr();
$sth->execute() or die "execute failed: " . $sth->errstr();
($client_id) = $sth->fetchrow();

#The line below keeps causing an error saying "client_id cannot be found"
die "client_id not found" unless defined $client_id;

# 2nd, for each mail_id in the table, grab the fname and print it on the page
while (($client_id) = $sth->fetchrow()) {
my $sth = $dbh->prepare("SELECT fname FROM tblClients WHERE client_id = $client_id")
or die "prepare failed: " . $dbh->errstr();
$sth->execute() or die "execute failed: " . $sth->errstr();
my($fname) = $sth->fetchrow();
print " $fname\n";
$sth->finish();
}

$sth->finish();

$dbh->disconnect();

#End page

Any help, tips or suggestions will be greatly appreciated. I've been stuck on this for 3 days. Thank you in advance
Mike