sub handler {

  my @items2show;
  ...
  checkForm (..., \@items2show);
  ...
  showPage (..., \@items2show);
  ...
}

##</code><code>##

use constant ARRAYX => 3;

##</code><code>##

sub checkForm {
  my (..., $items2show_ref) = @_;
  @$items2show_ref = ();
  $$items2show_ref[ARRAYX] = [];  # should this be () ??
  ...
  push @??ARRAYX??, $value;
  ...
}