Curious case of arithmetic expansion

[Florian Mayer]

Consider

$ foo=bar; bar=moo; moo=123
$ echo $foo $bar $moo
=> bar moo 123
$ echo $((foo))
=> 123 
$ echo $foo $bar $moo
=> bar moo 123
$ # so far so good but
$ ((foo++))
$ echo $foo $bar $moo
=> 123 moo 123

Now my chain of indirections is broken…