Joelle's solution to 29.1 in Perl 6

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+#!/usr/bin/env perl6
+use v6;
+
+# This handles the following:
+#
+#   a{1,2}
+#   a{1,2{3,4}}{5,6}b
+# 
+# And similar versions.  So, yes, you can nest and have multiple
+# curlies. Note there is no way to "quote" commas or curlies at this
+# time, but they would be reasonably straightforward to add (Perl 6 is
+# awesome).  Now to try to figure out how to do this in P5, without the
+# awesome grammars...
+#
+
+grammar Expansion {
+    rule TOP      {
+        ^
+        <element>*
+        $
+    }
+    token element  { <string> | <curly> }
+    token string   { <-[ \{ \} ]>+ }
+    token curly    { \{ <option>+ % ',' \} }
+    token option   { <innerstr> | <curly> }
+    token innerstr { <-[ \{ \} \, ]>* }
+}
+
+
+sub MAIN(Str:D $str) {
+    my $expanded = expand($str);
+
+    say $expanded.sort.unique.join("\n");
+}
+
+sub expand($str) {
+    my $parse = Expansion.parse($str);
+    die "Invalid String" unless $parse.defined;
+
+    return expansion([''], $parse);
+}
+
+# The magic happens here.  Basically it recursively calls itself as it
+# descends the tree.  Have I mentioned how much I love Perl 6 grammars?
+#
+# Note that string token is different than the innerstr, which looks
+# like duplicated code (I'm willing to live with a couple lines here)
+# but is not quite since string and innerstring *are* different - the
+# outter strings (outside any curlies) allows commas.
+sub expansion(@arr is copy, $tree) {
+    if $tree<element>:exists {
+        # Handle each element.
+        for @($tree<element>) -> $ele {
+            @arr = expansion(@arr, $ele);
+        }
+        return @arr;
+    } elsif $tree<string>:exists {
+        return @arr.map: { $_ ~ $tree<string> };
+    } elsif $tree<innerstr>:exists {
+        return @arr.map: { $_ ~ $tree<innerstr> };
+    } elsif $tree<curly>:exists {
+        my @arr-copy = @arr;
+        @arr = [];
+        for @($tree<curly><option>) -> $ele {
+            @arr.append: expansion(@arr-copy, $ele);
+        }
+        return @arr;
+    } else {
+        die;
+    }
+
+}
+