sub X
{
    my $self = shift;

    $self->{age} = 17;
}

##</code><code>##

sub X
{
    my $self = shift;

    print "\$self = $self\n";
    $self->{age} = 17;
    print "\$self = $self\n";
}

##</code><code>##

sub Z
{
     my ($foo) = @_;

     print "\$foo = $foo\n";
     $foo = 17;
     print "\$foo = $foo\n";
}

my $bar = 29;
print "\$bar = $bar\n";
Z($bar);
print "\$bar = $bar\n";

##</code><code>##

sub Z
{
     my ($foo) = @_;

     print "\$foo = $foo\n";
     $$foo = 17;
     print "\$foo = $foo\n";
}

my $bar = 29;
print "\$bar = $bar\n";
Z(\$bar);
print "\$bar = $bar\n";