Perl's default bitwise operators do differentiate between numbers and strings that look like numbers in a way that addition doesn't*, and the readline/glob operator <> does different things depending on what (if anything) is between the signs.

There's also the whole overload pragma for objects, which doesn't affect default data types, but if you're sufficiently perverse, you can define a String class that uses '+' like JavaScript.

* in 2015, they added new operators so that those and the original operators don't overload and have only one specific purpose if the bitwise ~~pragma~~ Edit: feature is turned on. You might know all this already though.