use strict, doesn't catch undefined variables in subroutines, that has the same name as variables outside, that has been declared, this causes hard to find bugs.

You don't want this. It is the entire point of strictures to be able to safely use a variable name without knowing whether it has been used before and not make code break.

If you want the opposite, then you're using quasi-globals. Instead, define variables in the smallest possible scope, so that they're not visible from anywhere other than where they get used.

Makeshifts last the longest.