You said

my $q = CGI->new; instead of  my $q = CGI->new( { } );
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. . . reads all the POST data and makes it unavailable to your main pr
+ogram
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Yes both, cases were true. I changed them and now everything is working fine. Just to confirm whether I am following good coding practice or not, below are my few doubts on same line.

1. myModule has following code in its new sub routine, does it has any flaws:

   sub new { 
       bless {}, shift 
   }
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2. How do I use relative name scheme? (instead, of using : use lib 'D:\\Websiste\\One\cgi-bin';) I tried earlier, but it failed. Normal CGI scripts and myModule are in same directory.
3. In myModule, I was using my $session = CGI::Session->load or die CGI::Session->errstr; at global scope to check sessions, before generating HTML contents. Now after your suggestion, I moved same code in each sub routine. But this duplicates code, and I have to write it in, every sub routine. Is there any work around for same. Or all session handling code should be put into different sub routine.

myModule has following code in its new sub routine, does it has any flaws:

I don't see any flaws with that "class method"

2. How do I use relative name scheme? (instead, of using : use lib 'D:\\Websiste\\One\cgi-bin';) I tried earlier, but it failed. Normal CGI scripts and myModule are in same directory.

?? File::FindLib - Find and use a file/dir from a directory above your script file
?? FindBin - Locate directory of original perl script

In myModule, I was using my $session = CGI::Session->load or die CGI::Session->errstr; at global scope to check sessions, before generating HTML contents. Now after your suggestion, I moved same code in each sub routine. But this duplicates code, and I have to write it in, every sub routine. Is there any work around for same. Or all session handling code should be put into different sub routine.

Um, try

sub new {
  my( $class, %args ) = @_;
  my $self        = bless { %args }, $class
  my $query       = CGI->new;
  my $sessionargs = $self->{sessionargs} || $default_sessionargs;
  my $session = CGI::Session->load(
      $sessionargs->{dsn}, $query, $sessionargs->{dsn_args},
  ) or die CGI::Session->errstr;
  $self->{query}   = $query;
  $self->{session} = $session;
  return $self;
}
sub param {
    my $self = shift;
    $self->{query}->param( @_ );
}
sub session { $_[0]->{session}; }
sub fandango {
    my( $self ) = @_;
    $self->param ...;
    ...;
    $self->session->param ...;
    ...;
}
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Things like that, see http://cgi-app.org//CGI::Application
http://mojolicio.us/perldoc/Mojolicious/Guides/Growing
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Hi, Anonymous Monk

This post, not only answers, my original questions, but would also clear my upcoming doubts, on same path. Thanks!

Testing, what you have said, and would communicate back results. Thanks for giving pointer.