Document that try/finally expressions take the value of the try block (#57663)

Close #56855

Author: IanButterworth

base/docs/basedocs.jl

@@ -1118,6 +1118,41 @@ normally), [`close(f)`](@ref) will be executed. If the `try` block exits due to
 the exception will continue propagating. A `catch` block may be combined with `try` and
 `finally` as well. In this case the `finally` block will run after `catch` has handled
 the error.
+
+When evaluating a `try/catch/else/finally` expression, the value of the entire
+expression is the value of the last block executed, excluding the `finally`
+block. For example:
+
+```jldoctest
+julia> try
+           1
+       finally
+           2
+       end
+1
+
+julia> try
+           error("")
+       catch
+           1
+       else
+           2
+       finally
+           3
+       end
+1
+
+julia> try
+           0
+       catch
+           1
+       else
+           2
+       finally
+           3
+       end
+2
+```
 """
 kw"finally"
 

doc/src/manual/control-flow.md

@@ -893,6 +893,41 @@ When control leaves the `try` block (for example due to a `return`, or just fini
 continue propagating. A `catch` block may be combined with `try` and `finally` as well. In this
 case the `finally` block will run after `catch` has handled the error.
 
+When evaluating a `try/catch/else/finally` expression, the value of the entire
+expression is the value of the last block executed, excluding the `finally`
+block. For example:
+
+```jldoctest
+julia> try
+           1
+       finally
+           2
+       end
+1
+
+julia> try
+           error("")
+       catch
+           1
+       else
+           2
+       finally
+           3
+       end
+1
+
+julia> try
+           0
+       catch
+           1
+       else
+           2
+       finally
+           3
+       end
+2
+```
+
 ## [Tasks (aka Coroutines)](@id man-tasks)
 
 Tasks are a control flow feature that allows computations to be suspended and resumed in a flexible