Support empty positional captures.

Author: jnthn

src/QRegex/P5Regex/Actions.nqp

@@ -85,7 +85,10 @@ class QRegex::P5Regex::Actions is HLL::Actions {
     }
 
     method p5metachar:sym<( )>($/) {
-        make QAST::Regex.new( $<nibbler>.ast, :rxtype<subcapture>, :node($/) );
+        make QAST::Regex.new( :rxtype<subcapture>, :node($/),
+            $<nibbler>
+                ?? $<nibbler>[0].ast
+                !! QAST::Regex.new( :rxtype<anchor>, :subtype<pass> ) );
     }
 
     method p5metachar:sym<[ ]>($/) {

src/QRegex/P5Regex/Grammar.nqp

@@ -59,7 +59,7 @@ grammar QRegex::P5Regex::Grammar is HLL::Grammar {
         '(?' {} <assertion=p5assertion>
         [ ')' || <.panic: "Perl 5 regex assertion not terminated by parenthesis"> ]
     }
-    token p5metachar:sym<( )> { '(' {} <nibbler> ')' }
+    token p5metachar:sym<( )> { '(' {} <nibbler>? ')' }
     token p5metachar:sym<[ ]> { <?before '['> <cclass> }
 
     token cclass {