The part that was/is challenging/mind blowing for me to grok was:

   sub flatten {
        my @f;
        push @f, (ref $_ ? flatten( $_ ) : $_ ) for @{ $_[0] };
        return @f;
    }

The implicit $_, and whatever @{ $_[0]} does, is challenging enough that I bet I could find people who had been using perl to do work for years who wouldn't be able to explain what was happening here at first glance, even if they could eventually work it out/write it themselves with a bit of effort.

That's what I meant by native iterative/sequence languages like python lend themselves to easy solutions for this type of question, even for people who aren't programmers, whereas you really need to be a programmer to come up with something as powerful as the above.

Put another way, doing a complex joined query might be a trivial question for someone who knows even the slightest amount of SQL, but would be beyond most novice python developers (without of course just using a SQL select statement...)

I will admit the (dense) perl solution certainly has its own beauty that the more drawn out python solution is lacking, though I'm guessing it could be written in a pythonic way itself...