make examples compile

Author: gfldex

doc/Language/functions.pod6

@@ -178,20 +178,23 @@ values.
 
 Perl 6 has many ways to specify a function's return type:
 
-    sub foo(--> Int)      {}; say &foo.returns # (Int)
-    sub foo() returns Int {}; say &foo.returns # (Int)
-    sub foo() of Int      {}; say &foo.returns # (Int)
-    my Int sub foo()      {}; say &foo.returns # (Int)
+=for code :skip-test
+sub foo(--> Int)      {}; say &foo.returns; # (Int)
+sub foo() returns Int {}; say &foo.returns; # (Int)
+sub foo() of Int      {}; say &foo.returns; # (Int)
+my Int sub foo()      {}; say &foo.returns; # (Int)
 
 Attempting to return values of another type will cause a compilation error.
 
-    sub foo() returns Int { "a"; }; foo; # Type check fails
+=for code :catch-all
+sub foo() returns Int { "a"; }; foo; # Type check fails
 
 Note that C<Nil> and C<Failure> are excempt from return type constraints and
 can be returned from any routine, regardless of its constraint:
 
-    sub foo() returns Int { fail   }; foo; # Failure returned
-    sub foo() returns Int { return }; foo; # Nil returned
+=for code :catch-all
+sub foo() returns Int { fail   }; foo; # Failure returned
+sub bar() returns Int { return }; bar; # Nil returned
 
 =head2 X<Multi-dispatch|declarator,multi>