Problems about ferret command "set axis/modulo "

[Chi <chi@xxxxxxxxx>]

Hi Jonathan and everyone
  I found a problem with ferret command "set axis/modulo". I have a 3D netcdf file,
the longitude are west and are defined as 
   longitude = -30, -29.5, -29, -28.5, -28, -27.5, -27;
  If I don't use "set axis/modulo" command, just set region using
set region/x="-27.5"/y="6.5":"11"/z="-200":"-1"/l=1, then everything is fine
  However, I found that the LAS generated ferret script called 
set axis/modulo to setup longitude as modulo, then it used 
set region/x="332.5"/y="6.5":"11"/z="-200":"-1"/l=1, but it didn't return the
correct data/image at the longitude -27.5, which is what I needed.
  I remembered that some perl source code of LAS said that since ferret won't process
negative west longitude well, then LAS automatically convert it to positive east-wise
value. However when I manually called ferret script to process my data using negative 
west longitude, everything was fine. It was the "set axis/modulo" command who caused 
me problems.
  Anybody can help me about this? Or How can I configure LAS not to use "sex axis/modulo"?
  Thanks a lot, Ding