#!/usr/bin/perl

use CGI;
$query = new CGI;

$topic_directory = "topics";

if($query->param('topic')){
     $topic = $query->param('topic');
     &file_error unless (&open_topic);
     &format_error unless (&parse_topic);
     &print_page_start;
     &print_topic;
     &print_response_form;
     print "<P>Return to the <A HREF=\"display.pl\">Topic
list</A>.</P>\n";
     &print_page_end;
}
else{
     &page_title = "Topic Index";
     &print_page_start;
     &print_topic_index;
     &print_page_end;
}

sub print_page_start{
    print $query->header;

sub print_topic_index{
     eval{
     opendir(TOPICS, "$topic_directory")
          or die "Can't open $topic_directory";
     @topics = grep (/^.+\.txt$/, readdir (TOPICS));
     foreach $topic (@topics){
          $topic =~ s/(.+)\.txt/$1/;
          &open_topic;
          &parse_topic;
          print "<A HREF=\"display.pl?topic=$topic\">";
          print "$page_title</A>, $topic_author<BR>\n";
}
};
}
........
.......#<CODE HERE WAS OMITTED>
The following code contains the form that holds the variable contents for
$topic   The problem that I am having is I do not understand how the topic
parameter in the form is passed a topic ID when it is a hidden field?  The
code for the form creation is below:


sub print_response_form{
     print "<FORM METHOD=\"post\" ACTION=\"post.pl\">\n";
     print "<INPUT TYPE=\"hidden\" NAME=\"action\" ";
     print "VALUE=\"response\">\n";
     print "<INPUT TYPE=\"hidden\" NAME=\"response_to\" ";
     print "VALUE=\"$topic\">\n";
     print "Author: ";
     print "<INPUT TYPE=\"text\" NAME=\"author\" ";
     print "SIZE=40 MAXLENGHT=72 VALUE=\"$author\"><BR>\n";
     print "Message body: <BR>\n";
     print "<TEXTAREA ROWS=10 COLS=60 NAME=\"post\";
     print "WRAP=\"virtual\">";
     print ".........
..................................
.