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doc/manual/source/language/expression/match.md

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+# Match Expression
+
+A `match` expression compares a target value against patterns from top to bottom and selects the first matching arm.
+
+```dcdl
+foo = match inputs.a.hoge {
+    >= 20: {
+        value = 200;
+    };
+    >= 10: {
+        value = 100;
+    };
+    _: {
+        value = 300;
+    };
+};
+```
+
+`_` is the fallback pattern.
+
+## Ordering
+
+Arms are ordered; Decodal does not automatically select the most specific pattern.
+If a broad condition appears first, narrower conditions after it are unreachable.