diff --git a/t/20-special-values.t b/t/20-special-values.t
new file mode 100644
index 0000000..c4725f2
--- /dev/null
+++ b/t/20-special-values.t
@@ -0,0 +1,254 @@
+use strict;
+use warnings;
+
+use Test::More tests => 33;
+
+# =============================================================
+# Test accessor behavior with special Perl values and edge-case
+# attribute names that exercise unusual but valid code paths:
+#   - Reference values (hashref, arrayref, coderef, blessed, regex)
+#   - Underscore-prefixed attributes (double-underscore hooks)
+#   - Object independence (no cross-talk between instances)
+#   - Builders returning references
+#   - Hook interaction with reference values
+# =============================================================
+
+# --- Reference values: store and retrieve various ref types ---
+{
+    package RefStore;
+    use Simple::Accessor qw{hash_val array_val code_val obj_val regex_val};
+
+    package main;
+
+    my $href  = { a => 1, b => 2 };
+    my $aref  = [10, 20, 30];
+    my $cref  = sub { 'hello' };
+    my $obj   = bless { id => 42 }, 'SomeClass';
+    my $regex = qr/^foo\d+$/;
+
+    my $o = RefStore->new(
+        hash_val  => $href,
+        array_val => $aref,
+        code_val  => $cref,
+        obj_val   => $obj,
+        regex_val => $regex,
+    );
+
+    is_deeply $o->hash_val,  $href,  'hashref round-trips through constructor';
+    is_deeply $o->array_val, $aref,  'arrayref round-trips through constructor';
+    is $o->code_val,  $cref,  'coderef round-trips through constructor';
+    is $o->obj_val,   $obj,   'blessed ref round-trips through constructor';
+    is $o->regex_val, $regex, 'regex ref round-trips through constructor';
+
+    # verify the coderef is callable
+    is $o->code_val->(), 'hello', 'stored coderef is callable';
+
+    # update reference value via setter
+    my $new_href = { x => 99 };
+    $o->hash_val($new_href);
+    is_deeply $o->hash_val, $new_href, 'hashref updated via setter';
+}
+
+# --- Builder returning a reference ---
+{
+    package RefBuilder;
+    use Simple::Accessor qw{config items};
+
+    my $config_calls = 0;
+
+    sub _build_config {
+        $config_calls++;
+        return { debug => 0, verbose => 1 };
+    }
+
+    sub _build_items { [qw(alpha beta gamma)] }
+
+    sub config_call_count { $config_calls }
+
+    package main;
+
+    my $o = RefBuilder->new();
+    is_deeply $o->config, { debug => 0, verbose => 1 },
+        'builder returning hashref works';
+    is_deeply $o->items, [qw(alpha beta gamma)],
+        'builder returning arrayref works';
+
+    # builder fires only once (reference is stored)
+    $o->config;
+    is( RefBuilder->config_call_count(), 1,
+        'builder returning ref fires only once' );
+}
+
+# --- Hooks receive and validate reference values ---
+{
+    package RefHooks;
+    use Simple::Accessor qw{data};
+
+    sub _validate_data {
+        my ($self, $v) = @_;
+        return ref $v eq 'HASH' ? 1 : 0;
+    }
+
+    sub _before_data {
+        my ($self, $v) = @_;
+        return 1;
+    }
+
+    package main;
+
+    my $o = RefHooks->new();
+    $o->data({ key => 'val' });
+    is_deeply $o->data, { key => 'val' },
+        'validate hook accepts hashref';
+
+    $o->data([1, 2, 3]);
+    is_deeply $o->data, { key => 'val' },
+        'validate hook rejects non-hashref (arrayref), old value kept';
+
+    $o->data('string');
+    is_deeply $o->data, { key => 'val' },
+        'validate hook rejects non-hashref (string), old value kept';
+}
+
+# --- After-hook rollback with reference values ---
+{
+    package RefRollback;
+    use Simple::Accessor qw{payload};
+
+    sub _after_payload {
+        my ($self, $v) = @_;
+        # reject arrayrefs, accept everything else
+        return ref $v eq 'ARRAY' ? 0 : 1;
+    }
+
+    package main;
+
+    my $original = { status => 'ok' };
+    my $o = RefRollback->new(payload => $original);
+    is_deeply $o->payload, $original, 'initial reference value set';
+
+    $o->payload([1, 2, 3]);
+    is_deeply $o->payload, $original,
+        'after-hook rollback restores original reference on rejection';
+
+    my $new_hash = { status => 'updated' };
+    $o->payload($new_hash);
+    is_deeply $o->payload, $new_hash,
+        'after-hook allows non-arrayref reference';
+}
+
+# --- Underscore-prefixed attribute: double-underscore hooks ---
+{
+    package PrivateAttr;
+    use Simple::Accessor qw{_data _count};
+
+    my $validate_called = 0;
+
+    # hook name: _build_ + _data = _build__data (double underscore)
+    sub _build__data { 'default-data' }
+
+    # hook name: _validate_ + _data = _validate__data
+    sub _validate__data {
+        my ($self, $v) = @_;
+        $validate_called++;
+        return length($v) > 0 ? 1 : 0;
+    }
+
+    sub _build__count { 0 }
+
+    sub validate_call_count { $validate_called }
+
+    package main;
+
+    my $o = PrivateAttr->new();
+    is $o->_data, 'default-data',
+        'underscore-prefix attr: builder _build__data fires';
+    is $o->_count, 0,
+        'underscore-prefix attr: builder _build__count fires';
+
+    $o->_data('new-value');
+    is $o->_data, 'new-value',
+        'underscore-prefix attr: setter works';
+    is( PrivateAttr->validate_call_count(), 1,
+        'underscore-prefix attr: _validate__data hook fires' );
+
+    $o->_data('');
+    is $o->_data, 'new-value',
+        'underscore-prefix attr: _validate__data rejects empty string';
+}
+
+# --- Object independence: no cross-talk between instances ---
+{
+    package IndependentObj;
+    use Simple::Accessor qw{name score};
+
+    sub _build_score { 0 }
+
+    package main;
+
+    my $a = IndependentObj->new(name => 'Alice');
+    my $b = IndependentObj->new(name => 'Bob');
+
+    is $a->name, 'Alice', 'instance A has its own name';
+    is $b->name, 'Bob',   'instance B has its own name';
+
+    $a->score(100);
+    is $a->score, 100, 'instance A score set to 100';
+    is $b->score, 0,   'instance B score unaffected (builder default)';
+
+    $b->score(200);
+    is $a->score, 100, 'instance A score still 100 after B update';
+    is $b->score, 200, 'instance B score updated to 200';
+
+    # reference value independence: modifying one shouldn't affect the other
+    my $a_data = { key => 'a' };
+    my $b_data = { key => 'b' };
+    $a->name($a_data);
+    $b->name($b_data);
+    $a_data->{key} = 'modified';
+    is $a->name->{key}, 'modified',
+        'instance A reflects mutation of stored reference';
+    is $b->name->{key}, 'b',
+        'instance B reference is independent from A';
+}
+
+# --- Overloaded object as attribute value ---
+{
+    package OverloadedVal;
+    use overload
+        '""'   => sub { "stringified:" . $_[0]->{val} },
+        'bool' => sub { 1 },
+        fallback => 1;
+
+    sub new { bless { val => $_[1] }, $_[0] }
+
+    package OverloadConsumer;
+    use Simple::Accessor qw{tag};
+
+    package main;
+
+    my $ov = OverloadedVal->new('test');
+    my $o = OverloadConsumer->new(tag => $ov);
+    is ref($o->tag), 'OverloadedVal',
+        'overloaded object stored as-is (not stringified)';
+    is "${\$o->tag}", 'stringified:test',
+        'overloaded stringification works on retrieved value';
+}
+
+# --- Builder returning blessed object ---
+{
+    package ObjBuilder;
+    use Simple::Accessor qw{engine};
+
+    sub _build_engine {
+        return bless { type => 'v8' }, 'Engine';
+    }
+
+    package main;
+
+    my $o = ObjBuilder->new();
+    isa_ok $o->engine, 'Engine',
+        'builder returning blessed ref preserves class';
+    is $o->engine->{type}, 'v8',
+        'builder-returned object has correct data';
+}