Return value (if you don't specify anything through $return) is the value of the last successfully matched items. The information can be found in the documentation in section 'Subrules':

The value associated with a subrule is the value associated with its $return variable (see "Actions" below), or with the last successfully matched item in the subrule match.

The second problem is that your print statement only belongs to the second rule, i.e. if Pre is matched, nothing is done at all. You might check the return value of your call to $p2->Format to see if a production was parsed successfully

The second problem is that your print statement only belongs to the second rule, i.e. if Pre is matched, nothing is done at all.

Wow, there is something I am not getting here. I would expect %item to have what matches in the rule, so if the rule is "Pre | Post", %item would have either the "Pre" or the "Post" matching part.

Obviously I am getting all this wrong

citromatik

You are right, %item has either the Pre or Post matching part. But only in one case does it print anything!

Entry      : Pre | Post
  { use Data::Dumper; print Dumper \%item;}

# is equivalent to

Entry : Pre 
Entry : Post
  { use Data::Dumper; print Dumper \%item; }

# is equivalent to

Entry : Post
  { use Data::Dumper; print Dumper \%item; }
Entry : Pre

# is NOT equivalent to

Entry : Pre 
  { use Data::Dumper; print Dumper \%item; }
Entry : Post
 { use Data::Dumper; print Dumper \%item; }
[download]

And the last example is what you want

I get this when I try to run it:

                ERROR: Internal error in generated parser code!
                (Hint: Set $::RD_HINT (or -RD_HINT if you're using "pe
+rl -s")
               for hints on fixing these problems.)
Can't call method "Format" on an undefined value at ./temp.pl line 17.
[download]

When run with "$::RD_HINT" set, as it recommends, I get this:

                ERROR: Internal error in generated parser code!
                (Hint: Global symbol "%ite" requires explicit package 
+name at
               (eval 8) line 472. syntax error at (eval 8) line 475,
               near ") {" syntax error at (eval 8) line 480, near "}
               Parse::RecDescent::_trace" BEGIN not safe after errors-
               -compilation aborted at (eval 8) line 541. )
Can't call method "Format" on an undefined value at ./temp.pl line 20.
[download]

I'm using Perl version 5.12.

Update: Ok, the problem was that I copy-pasted the code, and one of the lines was broken from that. I've used the "download" link, and now it runs fine. (though with citromatik's original problem) (thanks, jethro!)

I don't have any problem running the example I posted in Perl 5.10:

#!/usr/bin/perl

use strict;
use warnings;
use Parse::RecDescent;

my $p2 = Parse::RecDescent->new(q(
                                hyphen     : "-"
                                option     : "a" | "b" | "c"
                                Format     : Entry(s)
                                Pre        : hyphen option
                                Post       : option hyphen
                                Entry      : Pre | Post
                                { use Data::Dumper; print Dumper \%ite
+m;}
));
$p2->Format('a-');
$p2->Format('-a');
[download]

output:

$VAR1 = {
          'Post' => '-',
          '__RULE__' => 'Entry'
        };
[download]

citromatik