Make something experimental again

docs/src/experimental.md

@@ -6,6 +6,10 @@ deal with significant changes to these features in future versions of
 Query.jl. At the same time any feedback on these features would be
 especially welcome.
 
+## Source as the first argument to standalone query commands
+
+Some standalone query commands accept the source argument as the first argument, in addition to accepting it via the pipe operator. For example, `source |> @map(_)` and @map(source, _)` are equivalent. These source-as-the-first-argument versions of the standalone query operators are considered experimental and might disappear in future releases.
+
 ## The `_` and `__` syntax
 
 This syntax only works in the standalone query commands. Instead of writing

docs/src/standalonequerycommands.md

@@ -18,21 +18,6 @@ df2 = df |>
 
 ## Standalone query operators
 
-All standalone query commands can either take a source as their first argument, or one can pipe the source into the command, as in the above example. For example, one can either write
-
-```julia
-df = df |> @groupby(_.a)
-```
-or
-```julia
-df = @groupby(df, _.a)
-```
-both forms are equivalent.
-
-The remaining arguments of each query demand are command specific.
-
-The following discussion will present each command in the version where a source is piped into the command.
-
 ## The `@map` command
 
 The `@map` command has the form `source |> @map(element_selector)`. `source` can be any source that can be queried. `element_selector` must be an anonymous function that accepts one element of the element type of the source and applies some transformation to this single element.