fix compilation test

doc/Language/grammar_tutorial.pod6

@@ -305,7 +305,7 @@ Will output exactly the same as the code above.  Symptomatic of the difference
 between Classes and Roles, a conflict like defining C<token quote> twice
 using Role composition will result in an error:
 
-=begin code
+=begin code :skip-test<compilation error>
 grammar Quoted-Quotes does Letters does Quote-Quotes does Quote-Other { ... }
 # OUTPUT: ... Error while compiling ... Method 'quote' must be resolved ...
 =end code

doc/Language/js-nutshell.pod6

@@ -183,7 +183,7 @@ to Numeric if they're different types, C<eq> will cast them to strings:
 =begin code
 say '1' eq '1'; # True
 say 1 eq '1';   # True
-=end code;
+=end code
 
 The inverse of C<eq> is C<ne> or C<!eq>.
 
@@ -207,7 +207,7 @@ have the same value, but different containers, will return false:
 =begin code
 say 1 === 1; # True
 say '1' === 1; # True
-say {} === {}  # False
+say {} === {};  # False
 
 my \hash = {};
 my %hash := hash;
@@ -225,7 +225,7 @@ library for in Node.js:
 say {a => 1} eqv {a => 1}; # True;
 
 my \hash = {};
-my %hash := hash
+my %hash := hash;
 say hash eqv %hash; # True
 =end code
 
@@ -264,7 +264,7 @@ console.log(typeof 'foo');      // string
 console.log('foo'.constructor); // String
 =end code
 
-=begin code
+=begin code :ok-test<WHAT>
 say 'foo'.WHAT; # (Str)
 =end code
 

doc/Language/modules.pod6

@@ -414,13 +414,15 @@ Be careful I<not> to put C<sub EXPORT> after L«C<unit> declarator|/syntax/unit
 If you do so, it'll become just a sub inside your package, rather than the special
 export sub:
 
+=begin code :skip-test<unit module can't work here>
     unit module Bar;
     sub EXPORT { %(Foo => &say) } # WRONG!!! Sub is scoped wrong
 
     # ---------
 
     sub EXPORT { %(Foo => &say) } # RIGHT!!! Sub is outside the module
     unit module Bar;
+=end code
 
 =head2 Finding Modules
 

doc/Language/temporal.pod6

@@ -77,7 +77,10 @@ This very variable is also used to compute the month of the year when the file w
 
 C<Duration> objects can be compared. This is used in
 
-     $^a.value<age> <=> $^b.value<age>
+=for code :preamble<my %metadata>
+     %metadata.sort({
+         $^a.value<age> <=> $^b.value<age>
+     });
 
 to sort the files by age.