package Tie::HashNKeys;
    use strict;

    sub TIEHASH {
        my $class = shift;
        bless {}, $class;
    }

    sub STORE {
         $_[0]->{ join $;, sort split /$;/, $_[1] } = $_[2];
    }

    sub FETCH {
        $_[0]->{ join $;, sort split /$;/, $_[1] };
    }

##</code><code>##

    tie my %hash, 'Tie::HashNKeys';
    $hash{'csUsers','csGroups'} = 'foo';
    print $hash{'csGroups','csUsers'};   ## prints 'foo'