use strict;

my %hash = {a=>'A', b =>'B'};
my @array = [1,2,3];
my $scalar = 'This is a scalar';

dummy(array=>@array, scalar=>$scalar, hash=>{a=>'A', b =>'B'});
dummy(array=>@array, scalar=>$scalar, hash=>%hash);
my $hashref = \%hash;
dummy(array=>@array, scalar=>$scalar, hash=>$hashref);

sub dummy {
   my %args = @_;
   my @a = @{$args{array}};
   my %h = %{$args{hash}};
   my $s = $args{scalar};

   print "scalar is:  $s\n",
      'array is: ', join(',', @a),"\n",
      "hash is:\n", map "$_ => $h{$_}\n", keys %h;
   print "--------\n";
}