Lots of questions here!

First off, remember that HTTP is a stateless protocol, which means that the server(s) do not share any data between requests. You need to do that explicitly, either by putting data in the url, or in a form, or in a session.

Sharing state between requests

You have essentially three options:

1. Using url parameters: myapp?rm=edit;user=1 produces a page, and adds user=1 to the relevant urls. E.g. myapp?rm=save;user=1. The next request finds the user id with $self->query->param('user').
2. Using form fields: The same request produces a form with a hidden field:

   <form action="myapp">
   <input type="hidden" name="rm" value="save">
   <input type="hidden" name="user" value="1">
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   The next request finds the user id with $self->query->param('user') as well.
3. using a session: The same request creates a session, stores user=>1 in it, and sends a cookie with the session id in it along with the output. The next request looks in the session for the "user" parameter.

How to use sessions with CGI::Application

Save yourself headaches, and install CGI::Application::Plugin::Session. Configuration is pretty straightforward. Usage is dead simple too:

sub edit {
    my $self = shift;
    my $user_id = $self->query->param( 'user' );
    $self->session->param( user => $user_id ); # store it
    ...
}

sub save {
    my $self = shift;
    my $user_id = $self->session->param( 'user' ); # retrieve it
    ...
}
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Form validation strategy

It's handy to have form display and form processing in separate methods. The general pattern of form processing is

1. Gather input
2. Validate input
3. • If invalid, display the form again with error messages
   • If valid, process the input

Something like this:

sub display_form {
   ...
}

sub process_form {
   my $self = shift;

   my @input = data_from_query_or_session();

   # use CAP::ValidateRM here
   my @errors = validate( $profile, @input );

   if( @errors ) {
      # HTML::FillInForm makes this easier
      return $self->display_form( @errors );
   }

   # submission was ok, process the data
   ...
}
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Hope that helps :)