One note about style:
You might find it cleaner, and I believe it is quicker, if you group your print statements or use a "heredoc".

print "abc\n";
print "def\n";
print "ghi\n";

becomes

print "abc\n", "def\n", "ghi\n";

or

print << EOD;
abc
def
ghi
EOD
[download]

You can do this as well with your  print MAIL section.

You have some pretty long parameter lists, you might want to consider named parameters.

Get rid of temporary variables:

use CGI qw(:cgi);

my $url = $_[0];
my $q = CGI->new();

  print $q->redirect(
                   -url    => $url
                  );

# becomes

my $q = CGI->new();

  print $q->redirect(
                   -url    => $_[0]                  );
[download]

You use a lot of post-conditionals, and I tend to as well, but you may want to re-evaluate whether some of them make the code more difficult to read than others. A test is whether the condition or the result is "more important" and use that to determine which goes first.

&get_data (\$current_date, \$remote_host, 
           \$remote_addr, \$server_name);
#...
sub get_data {

my ($current_date, $remote_host, 
    $remote_addr, $server_name) = @_;
#....
    # get the information about who submitted the form
    $$remote_host = $ENV{'REMOTE_HOST'};
    $$remote_addr = $ENV{'REMOTE_ADDR'};
    $$server_name = $ENV{'SERVER_NAME'};
}
[download]

Why bother passing in the references? Just return the scalar values:

($current_date, $remote_host, 
  $remote_addr, $server_name) = get_data();

sub get_data {
#...
# get the current date
    ($day, $month, $year) = (localtime)[3,4,5];
    $year += 1900;
    return ( "$months[$month] $day, $year",
             $ENV{'REMOTE_HOST'}, $ENV{'REMOTE_ADDR'},
             $ENV{'SERVER_NAME'};
}
[download]

And just to restate, use CGI;

Hope this is useful.