Mark snippets from other languages

Only test Perl 6.

Author: coke

CONTRIBUTING.md

@@ -128,6 +128,13 @@ for a file. Use the pod-config option `skip-test` to skip them.
         your-example-here();
     =end code
 
+In other cases, the snippet of code isn't Perl 6; in that case, mark the
+language, which will also skip the test.
+
+    =begin code :lang<tcl>
+        puts "this is not Perl"
+    =end code
+
 ### Catching expected exception
 
 Some tests will throw exceptions that would stop the execution of the extracted

doc/Language/traps.pod6

@@ -195,7 +195,7 @@ Instead, use an expression that produces a value when you want a value.
 In Perl 5 one could reference the last element of an array by asking for the
 "-1th" element of the array, e.g.:
 
-=for code :skip-test<perl5>
+=for code :lang<perl5>
     my @array = qw{victor alice bob charlie eve};
     say @array[-1];    # OUTPUT: «eve␤»
 

xt/examples-compilation.t

@@ -57,10 +57,13 @@ my $counts = BagHash.new;
 for @files -> $file {
     for extract-pod($file.IO).contents -> $chunk {
         if $chunk ~~ Pod::Block::Code  {
+            if $chunk.config<lang> && $chunk.config<lang> ne 'perl6' {
+                next; # Only testing Perl 6 snippets.
+            }
             my $todo = False;
             if $chunk.config<skip-test> {
                 %*ENV<P6_DOC_TEST_FUDGE> ?? ($todo = True) !! next;
-        }
+            }
             @examples.push: %(
                 'contents', $chunk.contents.map({walk $_}).join,
                 'file', $file,