aded @@ for keyword swapping

tests/test_transpiler.py

@@ -102,3 +102,35 @@ def test_shebang_override():
 
 def test_shebang_default_when_absent():
     assert _check_shebang("si x:\n    pasar", "es") == "es"
+
+
+# ---------------------------------------------------------------------------
+# Postfix @@ syntax
+# ---------------------------------------------------------------------------
+
+def test_postfix_if():
+    out = es("x = 5\nx > 0 @@si:\n    imprimir(x)")
+    assert "if" in out
+    assert "@@" not in out
+
+def test_postfix_preserves_indentation():
+    src = (
+        "definir comprobar(x):\n"
+        "    x > 0 @@si:\n"
+        "        imprimir(x)\n"
+        "    sino:\n"
+        "        pasar\n"
+    )
+    out = es(src)
+    ast.parse(out)  # fails if indentation is broken
+
+def test_prefix_still_works_alongside_postfix():
+    src = (
+        "si x > 0:\n"
+        "    imprimir(x)\n"
+        "y < 0 @@si:\n"
+        "    imprimir(y)\n"
+    )
+    out = es(src)
+    assert out.count("if") == 2
+    assert "@@" not in out