.experimental can now be used to enable specific features

doc/manual.rst

@@ -1397,10 +1397,10 @@ dereferencing operations for reference types:
 
 Automatic dereferencing is also performed for the first argument of a routine
 call. But currently this feature has to be only enabled
-via ``{.experimental.}``:
+via ``{.experimental: "implicitDeref".}``:
 
 .. code-block:: nim
-  {.experimental.}
+  {.experimental: "implicitDeref".}
 
   proc depth(x: NodeObj): int = ...
 
@@ -5588,7 +5588,7 @@ dot operators
 -------------
 
 **Note**: Dot operators are still experimental and so need to be enabled
-via ``{.experimental.}``.
+via ``{.experimental: "dotOperators".}``.
 
 Nim offers a special family of dot operators that can be used to
 intercept and rewrite proc call and field access attempts, referring
@@ -6885,17 +6885,12 @@ is uncertain (it may be removed any time).
 Example:
 
 .. code-block:: nim
-  {.experimental.}
-  type
-    FooId = distinct int
-    BarId = distinct int
-  using
-    foo: FooId
-    bar: BarId
+  {.experimental: "parallel".}
 
   proc useUsing(bar, foo) =
-    echo "bar is of type BarId"
-    echo "foo is of type FooId"
+    parallel:
+      for i in 0..4:
+        echo "echo in parallel"
 
 
 Implementation Specific Pragmas
@@ -7917,7 +7912,7 @@ Example:
 
   # Compute PI in an inefficient way
   import strutils, math, threadpool
-  {.experimental.}
+  {.experimental: "parallel".}
 
   proc term(k: float): float = 4 * math.pow(-1, k) / (2*k + 1)