this({ 
        string => $string,
        times => 10,
    });

sub this {
    my $p = shift; # all params in hashref
    print $p->{string} x $p->{times};
}

##</code><code>##

my $href = { string => "Hello, world!" };
my $previous_error = $error;

this($href, $previous_error);

sub this {
    my $p = shift; # all params in hashref
    my $prev_error = shift;

    if (not $prev_error){
        print $p->{string};
    }
}

##</code><code>##

this();

sub this {
    my $p = shift;

    $p->{hostname} = $p->{hostname} || "0.pool.ntp.org";
    $p->{port} = $p->{port} || 123;
}