> I wonder why none[1] of the major dynamic languages offer the option of running with the built-in associative-data structures implemented using a Red-Black Tree. Seems like an obvious thing to do.

It's not a command-line option, but Perl lets you "tie" a hash to a different backing implementation, and there are some tree-based ones:

    use Tree::RB;
    tie my %hash, 'Tree::RB';