I've encountered several things where zsh's behaviour (in sh-mode) differs
from that of bash (in sh-mode). 

The attached script demonstrates the differences. When /bin/sh is bash,
the output is

ab
\y
$


When /bin/sh is zsh, the output is

a
b
y
\44


I'm undecided about which \ treatment inside of $'..' I prefer, so I guess
looking to what POSIX says is best. Regarding zsh's refusal to interpret
octal escapes that don't start with 0, I find that very annoying and it's
certainly not what most people expect. There are scripts out there that
will fail with sh=zsh because of this. I think this should be changed
(regardless of what POSIX says).

MSB

-- 
Indecision is the key to flexibility.