Using `==` in `expr` can lead to unintended behavior for strings that also qualify as doubles. One example being `if {$a == $b}` when a=1.0 and b=1. I imagine the reason `==` even works for strings post 8.4 is backwards compatibility with scripts that haven't replaced it with `eq` yet.

Is there a (simple) way to detect this at runtime, possibly finding all erroneous uses during test? Like activating a "strict" mode or something?