use strict ;
  use warnings ;

  try() ;        #     none: 1
  try(undef) ;   #    undef: 1
  try(-1) ;      #       -1: 0
  try(0) ;       #        0: 0
  try(1) ;       #        1: 1

  sub try {
    my ($s) = @_ ;

    my $r = validate_max_size(@_) ;

    if    (@_ == 0)      { $s = "none" ;  }
    elsif (!defined($s)) { $s = "undef" ; } ;

    printf "%8s: %d\n", $s, $r+0 ;
  } ;

  sub validate_max_size {
    my $val = shift;

    ! defined $val || $val > 0;
  }

##</code><code>##

  !defined($val) || ($val > 0) ;

##</code><code>##

  try('undef') ;  # Argument "undef" isn't numeric in numeric gt (>) ...