#!/usr/bin/perl --
use strict; use warnings;
use CGI::FormBuilder;

Main( @ARGV );
exit( 0 );

sub Main {
    
    my $cgi = CGI->new;

    # Our "mode" parameter determines what we do
    my $mode = $cgi->param('mode') || 'default';

    # Change our form based on our mode
    if ($mode eq 'view') {
        modeView( $cgi );
    } elsif ($mode eq 'edit') {
        modeEdit( $cgi );
    } else {
        modeDefault( $cgi );
    }
}

sub modeDefault { ... }
sub modeEdit { ... }
sub modeView {
    my ( $cgi ) = @_;
    my $form = CGI::FormBuilder->new(
        method => 'post',
        fields => [qw(...)],
        params => $cgi      # get CGI params
    );
    ...
    if ($form->submitted && $form->validate) {
        print $form->confirm;
    } else {
        print $form->render;
    }
}