I only glanced at your code, but I have two quick comments:

1) I like how you used <<'END_GRAMMAR' instead of q{...}. Escape slashes are simpler that way.

2) use strict and use warnings are suppiciously missing. Even if they are used in the .pl, they also need to be placed in the grammar as follows, if you wish for them to work for the "actions":

my $p = Parse::RecDescent->new( <<'END_GRAMMAR' );

{
   use strict;
   use warnings;
}

parse: ...
[download]