grep: bug or feature ?

[walter harms]

Hi list,
i was porting a script to an embedded box with bb and found the
following effect:

./busybox grep "[a-Z]" /etc/hosts
grep: bad regex '[a-Z]': Invalid range end

while
 grep "[a-Z]" /etc/hosts

works with no problem.

bug or feature ?


re,
 wh