if ( ref( $value ) ) {                   # <- that's a ref!
            # We have multiple values for this key
            foreach ( @$value ) {
                my $array_value = uri_escape( $_, $cgi_chars );
                $query_string .= "$key=$array_value&";
            }
        } else {
            $value = uri_escape( $value, $cgi_chars );
            $query_string .= "$key=$value&";
        }

##</code><code>##

        if ( ! ref( $value ) ) {
            $value = uri_escape( $value, $cgi_chars );
            $query_string .= "$key=$value&";
        } else {
            # We have multiple values for this key
            foreach ( @$value ) {
                my $array_value = uri_escape( $_, $cgi_chars );
                $query_string .= "$key=$array_value&";
            }
        }

##</code><code>##

    if(  UNIVERSAL::isa( $r, "ARRAY" )  ) {
        # access @$r here
    } elsif(  UNIVERSAL::isa( $r, "HASH" )  ) {
        # access %$r here

##</code><code>##

    if(  ref($r)  &&  "$r" =~ /(^|=)HASH/  ) {

##</code><code>##

sub method {
    my $self= shift;
    die "Invalid object" unless ref($self) eq "My::Package";

##</code><code>##

    die "Invalid object" unless UNIVERSAL::isa( $self, __PACKAGE__ );
# or
    die "Invalid object" unless eval { $self->isa(__PACKAGE__) };

##</code><code>##

if(  ref($r)  &&  "$r" =~ /=/  )