This gets around the package variable issue

package Data::Hash::Flatten;

use Storable qw(dclone);

sub this {
    my @args = ([], @_[1 .. $#_]);
    Data::Hash::Flatten->_flatten(@args);
}

sub _flatten {
    my (undef, $flattened, $href, $field, $depth, $flat_rec ) = @_;

    @$flattened = () unless defined($depth);

    if ( ref $href ) {
        my @key = keys %$href;
        for my $key_i ( 0 .. $#key ) {
            my $key = $key[$key_i];
            $flat_rec->{ $field->[$depth] } = $key;
            Data::Hash::Flatten->_flatten($flattened, $href->{$key},
                $field, $depth + 1, $flat_rec);
        }
    } else {
        $flat_rec->{ hits } = $href;
        my $new_rec = dclone $flat_rec;
        push @$flattened, $new_rec;
    }
    @$flattened;
}

package main;

use Data::Dumper;

my $a = {
    bill => { '5/27/96' => { 'a.dat' => 1, 'b.txt' => 2,
                             'c.lsp' => 3 } },
    jimm => { '6/22/98' => { 'x.prl' => 9, 'y.pyt' => 8,
                             'z.tcl' => 7 } }
};

my @a = Data::Hash::Flatten->this( $a, [qw(name date file)] );

print Dumper( \@a );
[download]

Hackish, but effective. Perhaps a better way around this is to re-write it as a class with methods and properties as opposed as to a function tucked away in it's own package.
HTH

_________
broquaint

update: changed code in this to suck less (wasn't passing the correct args)