Add examples of passing arguments to grammars

Demonstrate passing arguments to grammars

doc/Language/grammars.pod6

@@ -419,6 +419,65 @@ attributes can be accessed in the match returned after parsing if made public:
     # OUTPUT: [(Bool) True]
 =end code
 
+=head2 Passing arguments into grammars
+
+To pass arguments into a grammar, you can use the named argument of C<:args> on any of the parsing methods of grammar. The arguments passed should be in a C<list>.
+
+=begin code
+    grammar demonstrate-arguments {
+        rule TOP ($word) {
+        "I like" $word
+        }
+    }
+
+    # Notice the comma after "sweets" when passed to :args to coerce it to a list
+    say demonstrate-arguments.parse("I like sweets", :args(("sweets",))); # OUTPUT: «｢I like sweets｣␤»    
+=end code
+
+Once the arguments are passed in, they can be used in a call to a named regex inside the grammar.
+
+=begin code
+    grammar demonstrate-arguments-again
+        rule TOP ($word) {
+	   <phrase-stem><added-word($word)>
+        }
+
+        rule phrase-stem {
+	   "I like"
+	}
+
+        rule added-word($passed-word) {
+           $passed-word
+	}
+     }
+
+     say demonstrate-arguments-again.parse("I like vegetables", :args(("vegetables",)));
+     # OUTPUT: ｢I like vegetables｣␤»
+     # OUTPUT:  «phrase-stem => ｢I like ｣␤»
+     # OUTPUT:  «added-word => ｢vegetables｣␤»
+=end code
+
+Alternatively, you can initialise dynamic variables and use any arguments that way within the grammar.
+
+=begin code
+     grammar demonstrate-arguments-dynamic {
+         rule TOP ($*word, $*extra) {
+            <phrase-stem><added-words>
+	  }
+         rule phrase-stem {
+	    "I like"
+	 }
+         rule added-words {
+	    $*word $*extra
+	 }
+      }
+
+     say demonstrate-arguments-dynamic.parse("I like everything else", :args(("everything", "else")));
+     # OUTPUT: «｢I like everything else｣␤»
+     # OUTPUT:  «phrase-stem => ｢I like ｣␤»
+     # OUTPUT:  «added-words => ｢everything else｣␤»
+=end code
+
 X<|Actions>
 =head1 Action objects