I encountered a problem with variable substitution in the BASH shell.
Say you define a variable a. Then the command

    $> echo ${a//[0-4]/}

prints its value with all the numbers ranged between 0 and 4 removed:

    $> a="Hello1265-3World"
    $> echo ${a//[0-4]/}
    Hello65-World

This seems to work just fine, but let's take a look at the next example:

    $> b="?1265-3?"
    $> echo ${b//[0-4]/}
    ?1265-3?

Substitution did not take place: I assume that is because b contains CJK characters. This issue extends to all cases in which square brackets are involved. Surprisingly enough, variable substitution without square brackets works fine in both cases:

    $> a="Hello1265-3World"
    $> echo ${a//2/}
    Hello165-3World
    $> b="?1265-3?"
    $> echo ${b//2/}
    ?165-3?

Is it a bug or am I missing something?

I use Lubuntu 12.04, terminal is lxterminal and echo $BASH_VERSION returns 4.2.24(1)-release.

EDIT: Andrew Johnson in his comment stated that with gnome-terminal 4.2.37(1)-release the command works fine. I wonder whether it is a problem of lxterminal or of its specific 4.2.24(1)-release version.