Bash programmable completion of variable names

[Hal Burgiss]

I have a number of Ubuntu systems. On just one the tab expansion of shell
variables does not "work" as expected. Other types of completion work just
fine. And on all the other systems, tab completion of variables works fine.
For the life of me I cannot find where/how to turn this aspect on. I find
plenty of references of this on google, but not really troubleshooting type
help.

So on all systems except one, 

 cd $c/<TAB> ... expands to 
 cd /var/system/clients

on the problem system I get:

 cd $c/<TAB>
 cd \$c

$c is defined identically on all systems.

Thanks.

-- 
Hal