#!/usr/bin/perl

    use strict;
    use warnings;
    use CGI;

    require 'myroutines.pl';
    # other required routines here
    ...
    ...
  
    my $cgi = new CGI;

    my $JSCRIPT=<<EOF;

    // JS functions to validate user input
    ...
    ...
    EOF

   print $cgi->header();
   print $cgi->start_html(-Title=>'myTitle',
-script=>$JSCRIPT);
 
   ## code here ##

   if( $cgi->param('submit') {
   my $output1 = & subRoutine1(arg1,arg2..);
   ...
   ...
   my $output2 = & subRoutine2(arg1,arg2,arg3..);
   ...
   ...
   ### I've used several subroutines

   ### showing the output to the user
   
   }

   else {

   ### code to show form fields the user has to fill in
  
  }
   
   print $cgi->end_html;