[gradsusr] Multi-panel plots

[TYTECA Sophie]

Hello,

I want to use GrADS script function "panels.gsf" to draw multi-panel plot
all scripts are here: /opt/GrADS/lib and  GASCRP=/opt/GrADS/lib
I see in panels_demo.gs that I have to use "gsfallow" first, right?
See below my try :

Grid Analysis and Display System (GrADS) Version 2.0.1
Copyright (c) 1988-2011 by Brian Doty and the
Institute for Global Environment and Society (IGES)
GrADS comes with ABSOLUTELY NO WARRANTY
See file COPYRIGHT for more information

Config: v2.0.1 little-endian readline printim grib2 netcdf hdf4-sds hdf5 
opendap-grids,stn geotiff shapefile
Issue 'q config' command for more detailed configuration information
GX Package Initialization: Size = 8.5 11
ga-> open PLGEO500.ctl
Scanning description file:  PLGEO500.ctl
Data file PLGEO500.SG3.1959.dat is open as file 1
LON set to 0 360
LAT set to -87.864 87.864
LEV set to 500 500
Time values set: 1959:1:1:0 1959:1:1:0
E set to 1 1
ga-> rc = gsfallow("on")
Syntax Error:  Invalid Operand
   'gsfallow' not a variable or function name
   Error ocurred at column 1
DEFINE error:  Invalid expression.

thank you for your help