use strict;
use warnings;
use Data::Dumper;
sub one {
    return undef;
}
sub two {
    my @a = @_;
    print Dumper(\@a);
    return;
}
two(1,2,one(), 3);

##</code><code>##

$VAR1 = [1,2,undef,3];
$VAR1 = [1,2,3];

##</code><code>##

      sub read_file {
          my $file = shift;
          -f $file || return undef;  #file doesn't exist!

          #Continue reading file...
      }

      #and later...

      if ( my @data = read_file($filename) ){

          # if $filename doesn't exist,
          # @data will be (undef),
          # but I'll still be in here!

          process(@data);
      }
      else{

          # This is my error handling code.
          # I probably want to be in here
          # if $filname doesn't exist.

          die "$filename not found";
      }

##</code><code>##

      sub read_file {
          my $file = shift;
          -f $file || return;  #DWIM!

          #Continue reading file...
      }