Trying to get sort keys to work

[mario]

Hi -

One of the biggest frustrations with the "sort" utility is figuring out how to 
tell it where exactly the keys are on each line.  For example, I have a file which 
contains, in part,

MI#4617 ROM11  FAD_13 vss! vss! nmos  L=0.18U W=0.69U 
MI#4765 ROM0N  FAD_11 vss! vss! nmos  L=0.18U W=0.69U 
MI#4749 ROM8N  FAD_15 vss! vss! nmos  L=0.18U W=0.69U 

I really want to sort FIRST on column 3, and then on the numeric part of column 
2.  I would think that the sort command would be something like

sort -s -k3 -k2.4n

BUT this doesn't work.  It sorts OK on column 3, but then does nothing with the 
second sort key.

It would be incredibly useful if there were some mode in which sort would just 
report each line and the sort keys found on that line, so that I can make sure 
that I'm properly communicating how to find the darn keys!

-- Mario

% sort --version
sort (GNU coreutils) 5.97
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software.  You may redistribute copies of it under the terms of
the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and Paul Eggert.