Interesting, I wasn't aware of this trick to fool the parser. (I suppose the special symbols are put directly into the stash of the class)

Using _add instead of + as method name should make it easier.

But replacing ${\'+'} with $_add holding the code ref is the fastest.

Problems with chains do not exist.

Btw: Are you aware that Perl supports operater overloading?

(This won't be faster, rather slower but more readable)