Dynamic scope/binding is
super useful, but I do not agree tcl does it or does it well, because it's
not just shadowing the closure environment (ha), or changing globals in a dynamic-wind.
Perl's the only non-lisp I'm aware of that does dynamic binding well-enough to get the idea, but too many things just don't work:
local *int = sub { return 69 }; print int("42");
is a particularly annoying one: You just can't do it. Other names might have better chances, e.g.
package foo; sub int { 42 };
package main; sub a{local *foo::int = sub { return 69 };&b(@_);} sub b{goto \&foo::int};
print b("x"), a("x"), b("x"), a("x");
but this is a little unsatisfying.