Completing environmental variable names?

[Ludwig, Mark]

Has anyone written a hook to complete environmental variable
names?

Imagine that I have a variable named LONG_ENV_VAR_NAME, and
one called LONG_FOO_VAR_NAME.  If I'm finding a file (typing
its name in the minibuffer, the usual way), and after typing
"$LONG_E" I want to press TAB, and have it to complete it to
$LONG_ENV_VAR_NAME and then to expand its value (as it does
already).

I've become accustomed to this behavior in the T C Shell,
and frown when my beloved Emacs is less capable....

Thanks,
--
Mark Ludwig
Lifecycle Coll
Product Lifecycle Management

Siemens Industry Sector
Siemens Product Lifecycle Management Software Inc.
5939 Rice Creek Parkway
Shoreview, MN  55126 United States 
Tel.      :+1 (651) 855-6140
Fax      :+1 (651) 855-6280
ludwig.mark@siemens.com 
www.siemens.com/plm