sub isa
{
    my $self = shift;
    my ($type) = @_;

    my %is_builtin = map { $_ => 1 } qw(
        HASH ARRAY SCALAR CODE GLOB
    );

    return 0 if $is_builtin{$type};
    return $self->SUPER::isa($type);
}

##</code><code>##

sub can_stringify
{
    my ($thingy) = @_;

    return 1 unless ref $thingy;
    return 0 unless blessed $thingy;
    return $thingy->can('STRINGIFY');
}

##</code><code>##

if (UNIVERSAL::can($x, 'can') && $x->can('(""'))
{
    # Do stuff here
}