Try this simple demo

#!perl
use strict;
use CGI;
use CGI::Carp 'fatalsToBrowser'; # remove for prod

my %groupname = (
  ''=>'',
  1=>'11111',
  2=>'22222',
  3=>'33333',
  4=>'44444',
);

my $q = new CGI;
my $group = $q->param('group');

print $q->header,$q->start_html('test');
print qq!
<form>Select Group <select name="group" onChange="submit()">!;
for my $id (sort keys %groupname){
  my $sel = ($id eq $group) ? 'SELECTED' : '';
  print qq!<option value="$id" $sel>$groupname{$id}</option>!;
}
print q!</select></form><hr/>!;
  
#Information Table
if ($group){
  print qq!
 <table border="1" cellpadding="10" cellspacing="0">
  <h3> $groupname{$group} </h3>
  <tr>
   <td>Members of group: $group</td>
   <td>Jobs that group $group can do:</td>
  </tr>
  <tr>
   <td>Text on the way</td>
   <td>Text on the way</td>
  </tr>
 </table>!;
 } else {
   print "<h3>SELECT GROUP</h3>";
 }
print $q->end_html;
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poj