If somebody goes out of their way to tie $x before invoking lambda $x => sub { $x**2 }, then I think they would also be surprised to have that tie have no impact each time sub { $x**2 } gets called.

It seemed ‘obvious’ to me that, after a local $x, I should be able to assume that I'm in the same state as if $x had just been freshly declared, regardless of what happened in the outer scope; but I find this an excellent argument for why that would be a bad way to arrange things.