my %hash = ( 'This'  => 1,
             'That'  => 2,
             'Other' => 3 );
my @array = ( 1, 2, 3, 4, 5 );
my $scalr = "Hello World!\n";

mytest ( \%hash, \@array, $scalr );

sub mytest {
    my $h_ref = shift;
    my $a_ref = shift;
    my $simple = shift;
    local $, = ", ";
    print $h_ref->{$_}, "\n" foreach keys %{$h_ref};
    print $_, "\n" foreach @{$a_ref};
    print $simple, "\n";
}