tell how return relates to outer scopes

Author: gfldex

doc/Language/control.pod6

@@ -687,6 +687,12 @@ exception L<X::TypeCheck::Return|/type/X::TypeCheck::Return> is thrown. If it
 passes a control exception is raised and can be caught with
 L<CONTROL|/language/phasers#CONTROL>.
 
+Any C<return> in a block is tied to the outer lexical scope of that block.
+Please note that a C<return> in the root of a package will fail at runtime. A
+C<return> in a block that is evaluated lazily (e.g. inside C<map>) may find the
+outer lexical routine gone by the time the block is executed. In almost any
+case C<last> is the better alternative.
+
 =comment TODO add link to section in /language/function that shows how return values are produces/handled
 
 =head1 X<return-rw|control flow>