Returning to previous page

This question is really for Lambda, and is a refinement of an earler CGI question which he helped solve.

If you will go to this page (a website I'm developing) you will see an email newsletter button on the bottom right.

http://www.mdsutton.com/auto-1.html

After the person fills out their name and email address they are sent to a "thank you" page -- with a button that they click that will send them back to whatever page they were previously on.  This email newsletter subscription is on almost every other page of this webiste, in different directories, etc.

But the "Thank You" page script sends them back to the right page.

Here is the script (I slightly modified from the BigNoseBIrd website) that I used to make this happen.  I would like this "return to previous page" feature added to the "Email Article" script that you helped modify and get working.

(FOllowing that is the final verison of the "email article" script from the
previous CGI Experts exchange question)
#! /usr/local/bin/perl
# Be sure that the line above points to where perl 5 is
# on your system.  Modified by rowby

##################################################################
# subscribe.cgi: subscription e-mail collector with subscribe
# and unsubscribe features.
# Release 1.0 on 04/17/99
# (C) 1999 BigNoseBird.Com, Inc. This program is freeware and may
# be used at no cost to you (just leave this notice intact).
# Feel free to modify, hack, and play  with this script.
# It is provided AS-IS with no warranty of any kind.                
# We also cannot assume responsibility for either any programs      
# provided here, or for any advice that is given since we have no  
# control over what happens after our code or words leave this site.
# Always use prudent judgment in implementing any program- and      
# always make a backup first!                                      
#
##################################################################

# When calling the script, you must provide the following INPUTs
#
#   datafile  (name of file that will contain the addresses.)
#   email  (the e-mail address of the person subscribing/unsubscribing
#   action (subscribe or unsubscribe)

#### USER CONFIGURATION SECTION ##################################

# set BASEDIR to the directory that will hold your letter and
# mailling list files. Be certain that the script has permission
# to write to this directory. This must be set to the same value
# you declare in nmmdadmin.cgi

   $BASEDIR="/web/guide/mdsutton/cgibin/";

# remove the # mark before okaydomains to restrict subscription
# requests to your web site. This prevents others from calling
# your script from elsewhere. If you encourage others to offer
# your newsletter from their sites, do NOT remove the # mark.

#   @okaydomains=("http://mydomain.com", "http://www.mydomain.com");    

# $delimiter is the special character that is used to separate the
# items of information about each e-mail address. To use the TAB
# character, uncomment (remove the # mark) the line that says TAB
# and place a # mark at the start of the line that says PIPE.

   $delimiter="\\|"; #PIPE
#   $delimiter="\\t"; #TAB

##################################################################

   $lockfile="/tmp/subscribe.lck";

   &valid_page;
   &decode_vars;
   $return_to=$ENV{'HTTP_REFERER'};
   $the_date=localtime();
   $ip_addr=$ENV{'REMOTE_ADDR'};
   $datafile="$fields{'datafile'}\.mbz";
   $email=$fields{'email'};
   $action=$fields{'action'};

   if ($datafile eq "")
     { print "Content-type: text/html\n\n";
       print "Configuration Error: No datafile specified\n";
       exit;
     }
   if ($action eq "")
     { print "Content-type: text/html\n\n";
       print "Configuration Error: No action specified\n";
       exit;
     }

   if (&valid_address($email) == 0)  
     {
      &bad_email;
      exit;
     }

   &write_data;
   &thank_you;

sub thank_you
{
  if ($action eq "unsubscribe")
    { $whichaction = "removed from";}
    else { $whichaction = "added to";}
print "Content-type: text/html\n\n";
print <<__END_THANKS__;
<body background="http://www.mdsutton.com/images/line-bg1.gif">

<CENTER>
<TABLE WIDTH="510" BORDER="0" CELLPADDING="3" BGCOLOR="#FFFFFF">
</table>
</center>
<div align="center">
  <center>
  <table>

 <TR>
 <TD>
  <TABLE WIDTH="637" BORDER="0" CELLPADDING="5" BGCOLOR="#FFFFFF">
   <TR>
    <TD width="520">
      <CENTER>
      <FONT FACE="ARIAL">
      <font color="#800000" size="4" face="ARIAL"><b>
      &nbsp; Thank You!</b></font>
      <p>
      <B><font color="#000080">You have been $whichaction the M.D. Sutton
      Newsletter e-mail list.&nbsp; <br>
      <i>You will receive your first issue soon.</i></font><font color="#800000"><br>
      <BR>
      </font>
      <A HREF="$return_to"><img border="0" src="http://www.mdsutton.com/images/click-prev-page.gif" width="192" height="86">
    </TD>
    <TD width="117" valign="middle">
      <FONT FACE="ARIAL">
     
<img border="0" src="http://www.mdsutton.com/images/mike-with-name.gif" align="left" width="106" height="140">
    </TD>
   </TR>
  </TABLE>
  </TD>
 </TR>
    </table>
   </center>
  </div>

__END_THANKS__
}

##################################################################
sub write_data
{
   &get_datetime;
   $delim=$delimiter;
   $delim=~s/\\//g;
   &get_the_lock;
   open(IDBFILE,"<$BASEDIR$datafile");
   @mailing=<IDBFILE>;            
   close(IDBFILE);            

   open(ODBFILE,">$BASEDIR$datafile");
   foreach $line (@mailing)    
    {
      chop $line;
      ($thismail,$thisip,$thisdate)=split(/$delimiter/,$line);
      if ($email ne $thismail)
       {
        print ODBFILE "$line\n";
       }
    }
   if ($action eq "subscribe")
    {
     print ODBFILE "$email$delim$ip_addr$delim$rd$delim\n";
    }
   close (ODBFILE);
# This may seem a silly place to check to see if we were able to
# create the file, but a lot of people don't have access to their
# error logs to find message written by "die"
   &drop_the_lock;
   if (!-w "$BASEDIR$datafile")
     { print "Content-type: text/html\n\n";
       print "Configuration Error: could not create datafile
              please check path and permissions!\n";
       exit;
     }

}

##################################################################
sub decode_vars
 {
  $i=0;
  read(STDIN,$temp,$ENV{'CONTENT_LENGTH'});
  @pairs=split(/&/,$temp);
  foreach $item(@pairs)
   {
    ($key,$content)=split(/=/,$item,2);
    $content=~tr/+/ /;
    $content=~s/%(..)/pack("c",hex($1))/ge;
    $content=~s/\t/ /g;
    $content=~tr/A-Z/a-z/;
    $fields{$key}=$content;
   }
}

##################################################################
sub valid_address
 {
  local($testmail) = @_;
  if ($testmail eq "")
   {return 0;}
  if ($testmail =~ /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/ ||
  $testmail !~ /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/)
   { return 0;}
   else
    { return 1;}
}

##################################################################
sub bad_email
{
print <<__STOP_OF_BADMAIL__;
Content-type: text/html

<body background="http://www.mdsutton.com/images/line-bg1.gif">

<CENTER>
<TABLE WIDTH="510" BORDER="0" CELLPADDING="3" BGCOLOR="#FFFFFF">
</table>
</center>
<div align="center">
  <center>
  <table>

 <TR>
 <TD>
  <TABLE WIDTH="637" BORDER="0" CELLPADDING="5" BGCOLOR="#FFFFFF">
   <TR>
    <TD width="520">
      <CENTER>
      <FONT FACE="ARIAL">
      <font color="#800000" size="4" face="ARIAL"><b>
      &nbsp; Sorry!&nbsp;</b></font>
      <B><font color="#000080"><br>
      Your request to join the M.D. Sutton Newsletter could not be processed because your email address was not properly entered. Please enter it this way:
      &quot;yourname\@somewhere.com&quot;. <br>
      </font><font color="#800000">
      <BR>
      </font>
      <A HREF="$return_to"><img border="0" src="http://www.mdsutton.com/images/click-prev-page.gif" width="192" height="86">
    </TD>
    <TD width="117" valign="middle">
      <FONT FACE="ARIAL">
     
<img border="0" src="http://www.mdsutton.com/images/mike-with-name.gif" align="left" width="106" height="140">
    </TD>
   </TR>
  </TABLE>
  </TD>
 </TR>
    </table>
   </center>
  </div>
__STOP_OF_BADMAIL__
}

##################################################################
sub get_the_lock
{
  local ($endtime);                                  
  $endtime = 60;                                      
  $endtime = time + $endtime;                        
  while (-e $lockfile && time < $endtime)
   {
    # Do Nothing                                    
   }                                                  
   open(LOCK_FILE, ">$lockfile");                    
}

##################################################################
sub drop_the_lock
{
  close($lockfile);
  unlink($lockfile);
}

##################################################################
sub get_datetime
{
   %mos = ( "jan","01", "feb","02", "mar","03", "apr","04",            
            "may","05", "jun","06", "jul","07", "aug","08",
            "sep","09", "oct","10", "nov","11", "dec","12");
   $date=localtime(time);                                              
   ($day, $month, $num, $time, $year) = split(/\s+/,$date);            
   @time_temp=split(/\:/,$time);                                        
   $month=~tr/A-Z/a-z/;                                                
   $rd="$mos{$month}\/$num\/$year $time_temp[0]\:$time_temp[1]\:$time_temp[2]";
}


##################################################################
sub valid_page
 {
  if (@okaydomains == 0)
     {return;}
  $DOMAIN_OK=0;                                        
  $RF=$ENV{'HTTP_REFERER'};                            
  $RF=~tr/A-Z/a-z/;                                    
  foreach $ts (@okaydomains)                            
   {                                                    
     if ($RF =~ /$ts/)                                  
      {                                                
        $DOMAIN_OK=1;                                  
      }                                                
   }                                                    
   if ( $DOMAIN_OK == 0)                                
     {                                                  
      print "Content-type: text/html\n\n Sorry....Cant run from here!";    
      exit;                                            
     }                                                  
 }


=====
Now here's the working version of the Email article script where I would like the "RETURN TO PREVIOUS PAGE feature added"

#! /usr/local/bin/perl
use CGI;

$q=new CGI;
$friendname=$q->param("friend_name");
$friendmail=$q->param("friend_mail");
$sendername=$q->param("sender_name");
$sendermail=$q->param("sender_mail");
$articlename = "I asked M.D. Sutton to send you this Informative article";

#The article name can be passed as hidden field.
$filePath = "/mnt/web/guide/mdsutton/cgibin/email_articles/test-article.txt";
# the absolute path to the file.
open (FILE, $filePath) || die "cant open $filePath...$!";
while (<FILE>)
{
  $articlebody .= $_;
}
close (FILE);

$mail_program = "/usr/sbin/sendmail -t";
open (MAIL, "|$mail_program") || die ("Could Not Open Mail Program");
print MAIL "To: $friendname <$friendmail>\n";
print MAIL "From: $sendername <$sendermail>\n";
print MAIL "Subject: $articlename\n\n";
print MAIL $articlebody;
close (MAIL);

print "Content-type: text/html\n\n";
open (HTML_FILE, "/mnt/web/guide/mdsutton/cgibin/email_articles/success_msg.html") || die "cant open the html file";
@Success_Html = <HTML_FILE>;
close(HTML_FILE);

foreach (@Success_Html)
{
  print $_;
}
;