As an alternative, here's something I regularly use some variation of (Update: examples: 1, 2, 3) to output strings or other small data structures as part of my debug output:

sub pp {
    die "bad number of args to pp" unless @_==1;
    return Data::Dumper->new([shift])->Terse(1)->Purity(1)->Useqq(1)
        ->Quotekeys(0)->Sortkeys(1)->Indent(0)->Pair('=>')->Dump;
}
[download]

As for your question of wanting to load either one or the other module, here's an example of how I would have done it - with this, you can always use dd, no matter which module is available, although of course the output will look different:

BEGIN {
    if ( eval { require Data::Dump; 1 } )
        { Data::Dump->import('dd'); }
    else {
        require Data::Dumper;
        *dd = sub { print Data::Dumper->new(\@_)->Purity(1)
            ->Useqq(1)->Quotekeys(0)->Sortkeys(1)->Dump };
    }
}
[download]