diff --git a/source/strpool.hon b/source/strpool.hon
index e69de29..678bb27 100644
--- a/source/strpool.hon
+++ b/source/strpool.hon
@@ -0,0 +1,80 @@
+import "@std/mem"
+import "@std/arraylist"
+import "@std/hashmap"
+import "@std/testing"
+
+StringId :: alias usize
+
+StringPool :: struct {
+	ids hashmap.StringHashMap(StringId) # string → id
+	strings arraylist.ArrayList([]u8)   # id → owned string
+	allocator mem.Allocator
+}
+
+init func(allocator mem.Allocator) StringPool {
+	return StringPool{
+		ids = hashmap.init(allocator),
+		strings = arraylist.init(allocator),
+		allocator = allocator,
+	}
+}
+
+deinit func(pool @mut StringPool) void {
+	hashmap.deinit(&pool.ids)
+	for pool.strings.items |str| {
+		mem.free(pool.allocator, str)
+	}
+	arraylist.deinit(&pool.strings)
+}
+
+intern func(pool @mut StringPool, str []u8) StringId ! mem.AllocError {
+	if hashmap.get(&pool.ids, str) |id| return id
+
+	id :: pool.strings.items.len
+	owned_str []mut u8 :: try mem.alloc(u8, pool.allocator, str.len)
+	errdefer mem.free(pool.allocator, owned_str)
+	memcopy!(owned_str, str)
+
+	try arraylist.append(&pool.strings, owned_str)
+	errdefer _ = arraylist.pop(&pool.strings)
+
+	hashmap.put(&pool.ids, owned_str, id) catch |err| {
+		match err {
+			.key_exists: unreachable
+			else: return err
+		}
+	}
+
+	return id
+}
+
+get_str func(pool @StringPool, id StringId) ?[]u8 {
+	if (id >= pool.strings.items.len) return null
+	return pool.strings.items[id]
+}
+
+get_id func(pool @StringPool, str []u8) ?StringId {
+	return hashmap.get(&pool.ids, str)
+}
+
+handles_intern test {
+	pool StringPool = init(mem.c_allocator)
+	defer deinit(&pool)
+
+	input [5]mut u8 = ['h', 'e', 'l', 'l', 'o']
+	id :: try intern(&pool, input[..])
+	duplicate :: try intern(&pool, "hello")
+	input[0] = 'j'
+
+	same_id :: get_id(&pool, "hello")
+	mutated_id :: get_id(&pool, input[..])
+	hello_str :: get_str(&pool, id)
+	invalid_str :: get_str(&pool, id + 1)
+
+	try testing.expect_equal(0, id)
+	try testing.expect_equal(id, duplicate)
+	try testing.expect_equal(id, same_id?)
+	try testing.expect_equal(null, mutated_id)
+	try testing.expect_equal(null, invalid_str)
+	try testing.expect_equal("hello", hello_str?)
+}
diff --git a/std/arraylist/arraylist.hon b/std/arraylist/arraylist.hon
index 9088da7..4eb28d1 100644
--- a/std/arraylist/arraylist.hon
+++ b/std/arraylist/arraylist.hon
@@ -62,6 +62,13 @@ append func($T type, list @mut ArrayList(T), value T) void ! mem.AllocError {
 	return
 }
 
+pop func($T type, list @mut ArrayList(T)) ?T {
+	if (list.items.len == 0) return null
+	value :: list.items[list.items.len - 1]
+	list.items = list.items.ptr[..list.items.len - 1]
+	return value
+}
+
 clear func($T type, list @mut ArrayList(T)) void {
 	list.items = list.items.ptr[..0]
 }
diff --git a/std/testing/testing.hon b/std/testing/testing.hon
index 964dab3..e5e08c0 100644
--- a/std/testing/testing.hon
+++ b/std/testing/testing.hon
@@ -38,11 +38,9 @@ expect_equal func($T type, expected, actual T, location SourceLocation) void ! E
 			debug.print("{s}:{d}:{d}: expected and actual slices differ\n", {location.file, location.line, location.column})
 			return .expectation_failed
 		}
-		else: {
-			if expected != actual {
-				debug.print("{s}:{d}:{d}: expected {}, found {}\n", {location.file, location.line, location.column, expected, actual})
-				return .expectation_failed
-			}
+		else: if expected != actual {
+			debug.print("{s}:{d}:{d}: expected {}, found {}\n", {location.file, location.line, location.column, expected, actual})
+			return .expectation_failed
 		}
 	}
 }