Examples for overriding ws

Author: moritz

lib/Language/regexes.pod

@@ -761,6 +761,28 @@ Becomes:
 If a regex is declared with the C<rule> keyword, both the C<:sigspace> and
 C<:ratchet> adverbs are implied.
 
+Grammars provide an easy way to override what C«<.ws>» matches:
+
+    grammar Demo {
+        token ws {
+            <!ww>   # only match when no within a word
+            \h*     # only match horizontal whitespace
+        }
+        rule TOP {  # called by Demo.parse;
+            a b '.'
+        }
+    }
+
+    # doesn't parse, whitspace required between a and b
+    say so Demo.parse("ab.");       # False
+    say so Demo.parse("a b.");      # True
+    say so Demo.parse("a\tb .");    # True
+    # \n is vertical whitespace, so no match
+    say so Demo.parse("a\tb\n.");   # False
+
+When parsing file formats where some whitespace (for example vertical
+whitespace) is significant, it is advisable to override C<ws>.
+
 =head2 Matching Adverbs
 
 In contrast to regex adverbs, which are tied to the declaration of a regex,