Perl 6 also has dynamic scoping. But I don't think they kept it just for backward compatibility with Perl 4 & 5 :)

Here is another example where dynamic scoping can indeed be very useful:

    sub bar { 'bar' }
    sub baz { bar() }

    sub foo {
        no warnings 'redefine';
        local *bar = sub { 'My Bar' };
        baz();
    }

    say foo();   # => 'My Bar'
    say baz();   # => 'bar'