Curious case statement error

[pskocik]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I../. -I.././include -I.././lib  -D_FORTIFY_SOURCE=2 -g 
-O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat 
-Werror=format-security -Wall
uname output: Linux laptop 3.19.0-32-generic #37~14.04.1-Ubuntu SMP Thu Oct 22 
09:41:40 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.3
Patch Level: 11
Release Status: release

Description:

In the enclosed example ( based on 
http://unix.stackexchange.com/questions/303166/doesnt-work-the-bash-script-to-check-given-single-character-is-in-lower-case-or
 ), bash always echos Lowercase, whereas all dash, zsh, and ksh echo 
Lowecase/Uppercase pairs as expected.

Repeat-By:
    uplow:

        read d
        case $d in
            [a-z]) echo "Character is in Lowercase";;
            [A-Z]) echo "Character is in Uppercase";;
        esac
    
    test:
        for sh in bash dash ksh zsh; do echo $sh; $sh uplow <<<x; $sh uplow<<<X 
; echo ; done