use strict;
use warnings;
use CGI;
...
# first one, processes POST data if present
my $q = new CGI(); 
...
# passing the anon hash causes this CGI.pm object
# to read its params from the hash instead of
# the environment
my $q2 = new CGI({});

##</code><code>##

use strict;
use warnings;
use CGI;
...

my $q = new CGI(); 
...
if( $someRedirectCondition ) {
  my $q2 = new CGI({});
  $q2->param('copy' => $q->param('copy') );
  $q2->param('foo' => 'bar');
  $q2->param('qux' => 'baz');
  ...
  my $uri = "http://some.domain/and/a/path?" . $q2->query_string();
  print $q2->redirect( -uri => $uri );
  exit 0;
}